WorldWideScience

Sample records for downflow entrained flow

  1. Modelling, simulation, and optimisation of a downflow entrained flow reactor for black liquor gasification

    Energy Technology Data Exchange (ETDEWEB)

    Marklund, Magnus [ETC Energitekniskt Centrum, Piteaa (Sweden)

    2003-12-01

    Black liquor, a by-product of the chemical pulping process, is an important liquid fuel in the pulp and paper industry. A potential technology for improving the recovery cycle of energy and chemicals contained in the liquid fuel is pressurised gasification of black liquor (PGLG). However, uncertainties about the reliability and robustness of the technology are preventing a large-scale market introduction. One important step towards a greater trust in the process reliability is the development of simulation tools that can provide a better understanding of the process and improve performance through optimisation. In the beginning of 2001 a project was initiated in order to develop a simulation tool for an entrained-flow gasifier in PBLG based on CFD (Computational Fluid Dynamics). The aim has been to provide an advanced tool for a better understanding of process performance, to help with trouble shooting in the development plant, and for use in optimisation of a full-scale commercial gasifier. Furthermore, the project will also provide quantitative information on burner functionality through advanced laser-optical measurements by use of a Phase Doppler Anemometer (PDA). To this point in current project, three different concept models have been developed. The work has been comprised in a thesis 'Modelling and Simulation of Pressurised Black Liquor Gasification at High Temperature' and presented at Luleaa Univ. of Technology in Oct 2003. The construction of an atmospheric burner test rig has also been initiated. The main objective with the rig will be to quantify the atomisation performance of suitable burner nozzles for a PBLG gasifier that can be used as input for the CFD model. The main conclusions from the modelling work done this far can be condensed to the following points: From the first modelling results it was concluded that a wide spray pattern is preferable with respect to demand for long residence times for black liquor droplets and a low amount

  2. Entrained Flow Gasification of Biomass

    DEFF Research Database (Denmark)

    Qin, Ke

    The present Ph. D. thesis describes experimental and modeling investigations on entrained flow gasification of biomass and an experimental investigation on entrained flow cogasification of biomass and coal. A review of the current knowledge of biomass entrained flow gasification is presented....... Biomass gasification experiments were performed in a laboratory-scale atmospheric pressure entrained flow reactor with the aim to investigate the effects of operating parameters and biomass types on syngas products. A wide range of operating parameters was involved: reactor temperature, steam/carbon ratio......, excess air ratio, oxygen concentration, feeder gas flow, and residence time. Wood, straw, and lignin were used as biomass fuels. In general, the carbon conversion was higher than 90 % in the biomass gasification experiments conducted at high temperatures (> 1200 °C). The biomass carbon...

  3. Down-flow moving-bed gasifier with catalyst recycle

    Science.gov (United States)

    Halow, John S.

    1999-01-01

    The gasification of coal and other carbonaceous materials by an endothermic gasification reaction is achieved in the presence of a catalyst in a down-flow, moving-bed gasifier. Catalyst is removed along with ash from the gasifier and is then sufficiently heated in a riser/burner by the combustion of residual carbon in the ash to volatilize the catalyst. This volatilized catalyst is returned to the gasifier where it uniformly contacts and condenses on the carbonaceous material. Also, the hot gaseous combustion products resulting from the combustion of the carbon in the ash along with excess air are introduced into the gasifier for providing heat energy used in the endothermic reaction.

  4. Entrainment in vertical annular two-phase flow

    International Nuclear Information System (INIS)

    Sawant, Pravin; Ishii, Mamoru; Mori, Michitsugu

    2009-01-01

    Prediction of amount of entrained droplets or entrainment fraction in annular two-phase flow is essential for the estimation of dryout condition and analysis of post dryout heat transfer in light water nuclear reactors and steam boilers. In this study, air-water and organic fluid (Freon-113) annular flow entrainment experiments have been carried out in 9.4 and 10.2 mm diameter test sections, respectively. Both the experiments covered three distinct pressure conditions and wide range of liquid and gas flow conditions. The organic fluid experiments simulated high pressure steam-water annular flow conditions. In each of the experiments, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using a liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant et al. (2008a) for the prediction of entrainment fraction is further improved in this study in order to account for the existence of critical gas and liquid flow rates below which no entrainment is possible. Additionally, a new correlation is proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction condition. The improved correlation successfully predicted the newly collected air-water and Freon-113 entrainment fraction data. Furthermore, the correlations satisfactorily compared with the air-water, helium-water and air-genklene experimental data measured by Willetts (1987). (author)

  5. TREATMENT OF METHANOLIC WASTEWATER BY ANAEROBIC DOWN-FLOW HANGING SPONGE (ANDHS) REACTOR AND UASB REACTOR

    Science.gov (United States)

    Sumino, Haruhiko; Wada, Keiji; Syutsubo, Kazuaki; Yamaguchi, Takashi; Harada, Hideki; Ohashi, Akiyoshi

    Anaerobic down-flow hanging sponge (AnDHS) reactor and UASB reactor were operated at 30℃ for over 400 days in order to investigate the process performance and the sludge characteristics of treating methanolic wastewater (2 gCOD/L). The settings OLR of AnDHS reactor and of UASB reactor were 5.0 -10.0 kgCOD/m3/d and 5.0 kgCOD/m3/d. The average of the COD removal demonstrated by both reactors were over 90% throughout the experiment. From the results of methane producing activities and the PCR-DGGE method, most methanol was directly converted to methane in both reactors. The conversion was carried out by different methanogens: one closely related to Methanomethylovorans hollandica in the AnDHS retainted sludge and the other closely related to Methanosarcinaceae and Metanosarciales in the UASB retainted sludge.

  6. Experimental study of flow monitoring instruments in air-water, two-phase downflow

    International Nuclear Information System (INIS)

    Sheppard, J.D.; Hayes, P.H.; Wynn, M.C.

    1976-01-01

    The performance of a turbine meter, target flow meter (drag disk), and a gamma densitometer was studied in air-water, two-phase vertical downflow. Air and water were metered into an 0.0889-m-ID (3.5-in.) piping system; air flows ranged from 0.007 to 0.3 m 3 /sec (16 to 500 scfm) and water flows ranged from 0.0006 to 0.03 m 3 /sec (10 to 500 gpm). The study included effects of flow rate, quality, flow regime, and flow dispersion on the mean and fluctuating components of the instrument signals. Wire screen flow dispersers located at the inlet to the test section had a significant effect on the readings of the drag disk and gamma densitometer, but had little effect on the turbine. Further, when flow dispersers were used, mass flow rates determined from the three instrument readings and a two-velocity, slip flow model showed good agreement with actual mass flow rate over a three-fold range in quality; mass flows determined with the drag disk and densitometer readings assuming homogeneous flow were nearly as accurate. However, when mass flows were calculated using the turbine and densitometer or turbine and drag disk readings assuming homogeneous flow, results were scattered and relatively inaccurate compared to the actual mass flows. Turbine meter data were used with a two-velocity turbine model and continuity relationships for each phase to determine the void fraction and mean phase velocities in the test section. The void fraction was compared with single beam gamma densitometer results and fluid momentum calculated from a two-velocity model was compared with drag disk readings

  7. Particle Entrainment under Turbulent Flow Conditions

    Science.gov (United States)

    Diplas, Panayiotis

    2009-11-01

    Erosion, transportation and deposition of sediments and pollutants influence the hydrosphere, pedosphere, biosphere and atmosphere in profound ways. The global amount of sediment eroded annually over the continental surface of the earth via the action of water and wind is estimated to be around 80 billion metric tons, with 20 of them delivered by rivers to the oceans. This redistribution of material over the surface of the earth affects most of its physical, chemical and biological processes in ways that are exceedingly difficult to comprehend. The criterion currently in use for predicting particle entrainment, originally proposed by Shields in 1936, emphasizes the time-averaged boundary shear stress and therefore is incapable of accounting for the fluctuating forces encountered in turbulent flows. A new criterion that was developed recently in an effort to overcome the limitations of the previous approach will be presented. It is hypothesized that not only the magnitude, but also the duration of energetic near bed turbulent events is relevant in predicting grain removal from the bed surface. It is therefore proposed that the product of force and its duration, or impulse, is a more appropriate and universal criterion for identifying conditions suitable for particle dislodgement. Analytical formulation of the problem and experimental data are used to examine the validity of the new criterion.

  8. Flow regime mapping of vertical two-phase downflow in a ribbed annulus

    International Nuclear Information System (INIS)

    Kielpinski, A.L.

    1992-01-01

    Two-phase flow regimes have been mapped for vertical, cocurrent downflow in a narrow annulus which is partially segmented by the presence of longitudinal ribs. This geometry and flow condition has application to the analysis of a Large-Break Loss of Coolant Accident (LB-LOCA) in the production K-Reactor at the Savannah River Site (SRS). The ribbed annular geometry, particularly the presence of non-sealing ribs, gives rise to some unique phenomenological features. The flow behavior is influenced by the partial segmentation of the annulus into four quadrants or subchannels. A random element is induced by the natural bowing of the slender tubes; the width of the azimuthal flow path between two subchannels at a given axial location is indeterminate, and can take on any value between zero and the maximum clearance of 7.6 x l0 -4 m. When the rib gap is zero at a given location, it is at a maximum 180P away at the same axial location. The range of rib gaps is spanned in a single test section, as it would be also in a reactor assembly. As a result of these effects, flow regime maps obtained by other researchers for downflow in annuli are not accurate for defining flow regimes in a ribbed annulus. Flow regime transitions similar to those noted by, e.g., Bamea, were observed; the locations of these transitions were displaced with respect to the transition equations derived by Bamea. Experimental bubble rise velocity measurements were also obtained in the same test section. The bubble rise velocities were much higher than expected from the theory developed for slug bubbles in tubes, unribbed annuli, and rectangular channels. An elliptical-cap bubble rises faster than a slug bubble of the same area. Large, slug-shaped bubbles injected into the test section were observed to reduce in size as they rose, due to interaction with a longitudinal rib. They thereby adopted a shape more like an elliptical-cap bubble, hence rising faster than the original slug bubble

  9. Development of a down-flow hanging sponge reactor for the treatment of low strength sewage.

    Science.gov (United States)

    Yoochatchaval, Wilasinee; Onodera, Takashi; Sumino, Haruhiko; Yamaguchi, Takashi; Mizuochi, Motoyuki; Okadera, Tomohiro; Syutsubo, Kazuaki

    2014-01-01

    The process performance of a down-flow hanging sponge (DHS) reactor for treating low strength sewage (biochemical oxygen demand (BOD) 20-50 mg/L) was investigated in Bangkok, Thailand. The hydraulic retention time (HRT) was set at 4 h during the start-up period and was reduced to 1.5 h in a stepwise manner. Throughout the 300-day operational period, the DHS reactor shows high performance with respect to the removal of total suspended solid (>90% total suspended solid removal efficiency). No clogging of sponge media was observed in response to the self-digestion phenomena of the biofilm. At a HRT of 1.5 h, the BOD removal efficiency was sufficiently high (about 85%). The pathogen Escherichia coli and other coliform bacteria were removed almost completely as well (removal was 99.4% and 98.1%, respectively). Regarding the retained sludge activity measurement, the nitrite oxidation rate was higher than the ammonium oxidation rate (0.031 and 0.022 gram of nitrogen per gram of volatile suspended solids per day, respectively). In the 300 days of operation, the amount of excess sludge production was negligible. Thus, no sludge treatment system is required. Introduction of the DHS system in developing countries is recommended because this system requires a relatively small area, and has low electricity consumption and operation costs.

  10. A droplet entrainment model for horizontal segregated flows

    Energy Technology Data Exchange (ETDEWEB)

    Höhne, Thomas, E-mail: T.Hoehne@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) – Institute of Fluid Dynamics, P.O. Box 510119, D-01314 Dresden (Germany); Hänsch, Susann [Imperial College, Department of Mechanical Engineering, South Kensington Campus, London SW7 2AZ (United Kingdom)

    2015-05-15

    Highlights: • We further developed the flow morphology detection model AIAD. • An advanced droplet entrainment model was introduced. • The new approach is applied against HAWAC experiments. - Abstract: One limitation in simulating horizontal segregated flows is that there is no treatment of droplet formation mechanisms at wavy surfaces. For self-generating waves and slugs, the interfacial momentum exchange and the turbulence parameters have to be modeled correctly. Furthermore, understanding the mechanism of droplet entrainment for heat and mass transfer processes is of great importance in the chemical and nuclear industry. The development of general computational fluid dynamics models is an essential precondition for the application of CFD codes to the modeling of flow related phenomena. The new formulation for the interfacial drag at the free surface and turbulence parameters within the algebraic interfacial area density model (AIAD) represents one step toward a more physical description of free surface flows including less empiricism. The AIAD approach allows the use of different physical models depending on the local fluid morphology inside a macro-scale multi-fluid framework. A further step of improving the modeling of free interfaces lies within the consideration of droplet entrainment mechanisms. In this paper a new sub-grid entrainment model is proposed, which assumes that due to liquid turbulence the interface gets rough and wavy leading to the formation of droplets. Therefore, the droplet entrainment model requires the consideration of an additional droplet phase, which is described with an own set of balance equations in the spirit of the particle model. Two local key factors determine the rate of droplet entrainment: the liquid turbulent kinetic energy as well as the outward velocity gradient of the liquid relative to the interface motion. The new droplet entrainment approach is included into CFD simulations for attempting to reproduce existing

  11. Sulfate reduction in an entrained-flow black liquor gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Kymaelaeinen, M.; Janka, K. [Tampella Power, Tampere (Finland); Frederick, W.J.; Littau, M.; Sricharoenchaikul, V.; Jivakanun, N.; Waag, K. [Oregon State Univ., Corvallis, OR (United States). Dept. of Chemical Engineering

    1995-12-31

    Sulfate reduction and carbon conversion during pyrolysis and gasification of black liquor particles were experimentally studied in a laminar entrained-flow reactor. A model was also developed to simulate an entrained-flow black liquor gasifier. Experimental results were then compared to model calculations. Results indicated that carbon must be present to get a high degree of sulfate reduction during gasification. It is therefore important to balance the rates of carbon conversion and sulfate reduction. High local temperatures in the reactor should be avoided so that carbon does not convert too rapidly, but temperatures of nearly 1000 degrees C are required to achieve good sulfate reduction. It was suggested that a new equation was needed to adequately predict sulfate reduction in an entrained-flow black liquor gasifier. 12 refs., 8 figs., 5 tabs.

  12. Mixing and entrainment in hydraulically driven stratified sill flows

    DEFF Research Database (Denmark)

    Nielsen, Morten Holtegaard; Pratt, Larry; Helfrich, Karl

    2004-01-01

    The investigation involves the hydraulic behaviour of a dense layer of fluid flowing over an obstacle and subject to entrainment of mass and momentum from a dynamically inactive (but possibly moving) overlying fluid. An approach based on the use of reduced gravity, shallow-water theory with a cross......-interface entrainment velocity is compared with numerical simulations based on a model with continuously varying stratification and velocity. The locations of critical flow (hydraulic control) in the continuous model are estimated by observing the direction of propagation of small-amplitude long-wave disturbances...... that the reduced gravity model systematically underestimates inertia and overestimates buoyancy. These differences are quantified by shape coefficients that measure the vertical non-uniformities of the density and horizontal velocity that arise, in part, by incomplete mixing of entrained mass and momentum over...

  13. Entrained Flow Reactor Test of Potassium Capture by Kaolin

    DEFF Research Database (Denmark)

    Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao

    2015-01-01

    In the present study a method to simulate the reaction between gaseous KCl and kaolin at suspension fired condition was developed using a pilot-scale entrained flow reactor (EFR). Kaolin was injected into the EFR for primary test of this method. By adding kaolin, KCl can effectively be captured...

  14. Entrainment at a sediment concentration interface in turbulent channel flow

    Science.gov (United States)

    Salinas, Jorge; Shringarpure, Mrugesh; Cantero, Mariano; Balachandar, S.

    2016-11-01

    In this work we address the role of turbulence on entrainment at a sediment concentration interface. This process can be conceived as the entrainment of sediment-free fluid into the bottom sediment-laden flow, or alternatively, as the entrainment of sediment into the top sediment-free flow. We have performed direct numerical simulations for fixed Reynolds and Schmidt numbers while varying the values of Richardson number and particle settling velocity. The analysis performed shows that the ability of the flow to pick up a given sediment size decreases with the distance from the bottom, and thus only fine enough sediment particles are entrained across the sediment concentration interface. For these cases, the concentration profiles evolve to a final steady state in good agreement with the well-known Rouse profile. The approach towards the Rouse profile happens through a transient self-similar state. Detailed analysis of the three dimensional structure of the sediment concentration interface shows the mechanisms by which sediment particles are lifted up by tongues of sediment-laden fluid with positive correlation between vertical velocity and sediment concentration. Finally, the mixing ability of the flow is addressed by monitoring the center of mass of the sediment-laden layer. With the support of ExxonMobil, NSF, ANPCyT, CONICET.

  15. Characterization of Residual Particulates from Biomass Entrained Flow Gasification

    DEFF Research Database (Denmark)

    Qin, Ke; Lin, Weigang; Fæster, Søren

    2013-01-01

    Biomass gasification experiments were carried out in a bench scale entrained flow reactor, and the produced solid particles were collected by a cyclone and a metal filter for subsequent characterization. During wood gasification, the major part of the solid material collected in the filter is soot...

  16. Stability analysis for downflow in heated channels

    International Nuclear Information System (INIS)

    Sampaio, P.A.B. de.

    1985-01-01

    Stability and flow distribution are analysed for downflow in heated channels. It is shown that at low flow rates instabilities associated with the buoyancy forces may appear. A computer code in FORTRAN language to determine downflow distribution among n heated channels is presented. The model used to calculate downflow distribution and the onset of instability is compared with experiments performed in a test section with two parallel channels. (Author) [pt

  17. Laboratory simulations of cumulus cloud flows explain the entrainment anomaly

    Science.gov (United States)

    Narasimha, Roddam; Diwan, Sourabh S.; Subrahmanyam, Duvvuri; Sreenivas, K. R.; Bhat, G. S.

    2010-11-01

    In the present laboratory experiments, cumulus cloud flows are simulated by starting plumes and jets subjected to off-source heat addition in amounts that are dynamically similar to latent heat release due to condensation in real clouds. The setup permits incorporation of features like atmospheric inversion layers and the active control of off-source heat addition. Herein we report, for the first time, simulation of five different cumulus cloud types (and many shapes), including three genera and three species (WMO Atlas 1987), which show striking resemblance to real clouds. It is known that the rate of entrainment in cumulus cloud flows is much less than that in classical plumes - the main reason for the failure of early entrainment models. Some of the previous studies on steady-state jets and plumes (done in a similar setup) have attributed this anomaly to the disruption of the large-scale turbulent structures upon the addition of off-source heat. We present estimates of entrainment coefficients from these measurements which show a qualitatively consistent variation with height. We propose that this explains the observed entrainment anomaly in cumulus clouds; further experiments are planned to address this question in the context of starting jets and plumes.

  18. Evaluation of Water Distribution and Oxygen Mass Transfer in Sponge Support Media for a Down-flow Hanging Sponge Reactor

    International Nuclear Information System (INIS)

    Uemura, S.; Okubo, T.; Maeno, K.; Takahashi, M.; Kubota, K.; Harada, H.

    2016-01-01

    A down-flow hanging sponge reactor has been developed for sewage treatment, mainly in developing countries. This novel reactor employs polyurethane sponge material as a support medium, which promises a proliferation of a large amount of biomass, offering excellent pollutant removal capability. Three types of sponge medium were evaluated with respect to water distribution and oxygen mass transfer. Water was supplied to the device, which consisted of 40 pieces of sponge media connected in series, and a tracer experiment was carried out. The ratios of actual hydraulic retention time to theoretical hydraulic retention time were in the range of 25-67% depending on the type of support medium. By supplying deoxygenated water from the top of the device, the overall volumetric oxygen transfer coefficient, K L a, was evaluated. Despite the non-aerated conditions, the K L a values of the support media were very high, in the range of 0.56-4.88 (1/min), surpassing those of other mechanically aerated processes. Furthermore, it was found that the suspended solids concentration in the influent played a role in increasing the actual hydraulic retention time/theoretical hydraulic retention time ratio, suggesting that managing the influent suspended solids concentration is prerequisite for preventing clogging problems in the down-flow hanging.

  19. Laboratory Studies of Anomalous Entrainment in Cumulus Cloud Flows

    Science.gov (United States)

    Diwan, Sourabh S.; Narasimha, Roddam; Bhat, G. S.; Sreenivas, K. R.

    2011-12-01

    Entrainment in cumulus clouds has been a subject of investigation for the last sixty years, and continues to be a central issue in current research. The development of a laboratory facility that can simulate cumulus cloud evolution enables us to shed light on the problem. The apparatus for the purpose is based on a physical model of cloud flow as a plume with off-source diabatic heating that is dynamically similar to the effect of latent-heat release in natural clouds. We present a critical review of the experimental data so far obtained in such facilities on the variation of the entrainment coefficient in steady diabatic jets and plumes. Although there are some unexplained differences among different data sets, the dominant trend of the results compares favourably with recent numerical simulations on steady-state deep convection, and helps explain certain puzzles in the fluid dynamics of clouds.

  20. Laboratory Studies of Anomalous Entrainment in Cumulus Cloud Flows

    International Nuclear Information System (INIS)

    Diwan, Sourabh S; Narasimha, Roddam; Sreenivas, K R; Bhat, G S

    2011-01-01

    Entrainment in cumulus clouds has been a subject of investigation for the last sixty years, and continues to be a central issue in current research. The development of a laboratory facility that can simulate cumulus cloud evolution enables us to shed light on the problem. The apparatus for the purpose is based on a physical model of cloud flow as a plume with off-source diabatic heating that is dynamically similar to the effect of latent-heat release in natural clouds. We present a critical review of the experimental data so far obtained in such facilities on the variation of the entrainment coefficient in steady diabatic jets and plumes. Although there are some unexplained differences among different data sets, the dominant trend of the results compares favourably with recent numerical simulations on steady-state deep convection, and helps explain certain puzzles in the fluid dynamics of clouds.

  1. Construction and demolition waste: Comparison of standard up-flow column and down-flow lysimeter leaching tests.

    Science.gov (United States)

    Butera, Stefania; Hyks, Jiri; Christensen, Thomas H; Astrup, Thomas F

    2015-09-01

    Five samples of construction and demolition waste (C&DW) were investigated in order to quantify leaching of inorganic elements under percolation conditions according to two different experimental setups: standardised up-flow saturated columns (<4mm particle size) and unsaturated, intermittent down-flow lysimeters (<40mm particle size). While standardised column tests are meant primarily to provide basic information on characteristic leaching properties and mechanisms and not to reproduce field conditions, the lysimeters were intended to mimic the actual leaching conditions when C&DW is used in unbound geotechnical layers. In practice, results from standardised percolation tests are often interpreted as estimations of actual release from solid materials in percolation scenarios. In general, the two tests yielded fairly similar results in terms of cumulative release at liquid-to-solid ratio (L/S) 10l·kgTS; however, significant differences were observed for P, Pb, Ba, Mg and Zn. Further differences emerged in terms of concentration in the early eluates (L/S<5l·kg(-1)TS) for Al, As, Ba, Cd, Cu, DOC, Mg, Mn, Ni, P, Pb, Sb, Se, Si, Zn. Observed differences between tests are likely to be due to differences in pH related to crushing and exposure of fresh particle surfaces, as well as in equilibrium conditions. In the case of C&DW, the standardised column tests, which are more practical, are considered to acceptably describe cumulative releases at L/S 10l·kg(-1)TS in percolation scenarios. However, when the focus is on estimation of initial concentrations for (for example) risk assessment, data from standardised column tests may not be fully applicable, and data from lysimeters may be used for validation purposes. Se, Cr and, to a lesser extent, SO4 and Sb were leaching from C&DW in critical amounts compared with existing limit values. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Absorption of CO2 and H2S in Aqueous Alkanolamine Solutions using a Fixed-Bed Reactor with Cocurrent Downflow Operation in the Pulsing Flow Regime

    NARCIS (Netherlands)

    Versteeg, G.F.; Swaaij, W.P.M. van

    1988-01-01

    Absorption rates of H2S and CO2 in several aqueous alkanolamines in a cocurrent downflow fixed-bed reactor operated in the pulse flow regime have been measured in order to obtain information on the potential selectivity and on the mass transfer parameters. From these experiments it can be concluded

  3. Dryout-type critical heat flux in vertical upward annular flow: effects of entrainment rate, initial entrained fraction and diameter

    Science.gov (United States)

    Wu, Zan; Wadekar, Vishwas; Wang, Chenglong; Sunden, Bengt

    2018-01-01

    This study aims to reveal the effects of liquid entrainment, initial entrained fraction and tube diameter on liquid film dryout in vertical upward annular flow for flow boiling. Entrainment and deposition rates of droplets were included in mass conservation equations to estimate the local liquid film mass flux in annular flow, and the critical vapor quality at dryout conditions. Different entrainment rate correlations were evaluated using flow boiling data of water and organic liquids including n-pentane, iso-octane and R134a. Effect of the initial entrained fraction (IEF) at the churn-to-annular flow transition was also investigated. A transitional Boiling number was proposed to separate the IEF-sensitive region at high Boiling numbers and the IEF-insensitive region at low Boiling numbers. Besides, the diameter effect on dryout vapor quality was studied. The dryout vapor quality increases with decreasing tube diameter. It needs to be pointed out that the dryout characteristics of submillimeter channels might be different because of different mechanisms of dryout, i.e., drying of liquid film underneath long vapor slugs and flow boiling instabilities.

  4. Free-surface entrainment into a rimming flow containing surfactants

    Science.gov (United States)

    Thoroddsen, S. T.; Tan, Y.-K.

    2004-02-01

    We study experimentally the free-surface entrainment of tubes into a steady rimming flow formed inside a partially filled horizontally rotating cylinder. The liquid consists of a glycerin-water mixture containing surfactants (fatty acids). The phenomenon does not occur without the surfactants and the details are sensitive to their concentration. The entrainment of numerous closely spaced air tubes and/or surfactant columns can start intermittently along a two-dimensional stagnation line, but is usually associated with the appearance of an axially periodic vortex structure, the so-called shark teeth, which fixes the spanwise location of these tubes. The number of tubes is governed by the three-dimensional shape of the free surface, reducing from more than 10 to only two in each trough, as the rotation rate is increased. The tubes vary in diameter from 10-30 μm and can extend hundreds of diameters into the liquid layer before breaking up into a continuous stream of bubbles and/or drops. The tubes are driven through the stagnation line by the strong viscous shear and are stretched in the downstream direction. The entrainment starts when the Capillary number Ca=μωR/σ≃0.4.

  5. Review Article: Advances in modeling of bed particle entrainment sheared by turbulent flow

    Science.gov (United States)

    Dey, Subhasish; Ali, Sk Zeeshan

    2018-06-01

    Bed particle entrainment by turbulent wall-shear flow is a key topic of interest in hydrodynamics because it plays a major role to govern the planetary morphodynamics. In this paper, the state-of-the-art review of the essential mechanisms governing the bed particle entrainment by turbulent wall-shear flow and their mathematical modeling is presented. The paper starts with the appraisal of the earlier multifaceted ideas in modeling the particle entrainment highlighting the rolling, sliding, and lifting modes of entrainment. Then, various modeling approaches of bed particle entrainment, such as deterministic, stochastic, and spatiotemporal approaches, are critically analyzed. The modeling criteria of particle entrainment are distinguished for hydraulically smooth, transitional, and rough flow regimes. In this context, the responses of particle size, particle exposure, and packing condition to the near-bed turbulent flow that shears the particles to entrain are discussed. From the modern experimental outcomes, the conceptual mechanism of particle entrainment from the viewpoint of near-bed turbulent coherent structures is delineated. As the latest advancement of the subject, the paper sheds light on the origin of the primitive empirical formulations of bed particle entrainment deriving the scaling laws of threshold flow velocity of bed particle motion from the perspective of the phenomenological theory of turbulence. Besides, a model framework that provides a new look on the bed particle entrainment phenomenon stemming from the stochastic-cum-spatiotemporal approach is introduced. Finally, the future scope of research is articulated with open questions.

  6. Measured gas and particle temperatures in VTT's entrained flow reactor

    DEFF Research Database (Denmark)

    Clausen, Sønnik; Sørensen, L.H.

    2006-01-01

    Particle and gas temperature measurements were carried out in experiments on VTTs entrained flow reactor with 5% and 10% oxygen using Fourier transform infrared emission spectroscopy (FTIR). Particle temperature measurements were performed on polish coal,bark, wood, straw particles, and bark...... and wood particles treated with additive. A two-color technique with subtraction of the background light was used to estimate particle temperatures during experiments. A transmission-emission technique was used tomeasure the gas temperature in the reactor tube. Gas temperature measurements were in good...... agreement with thermocouple readings. Gas lines and bands from CO, CO2 and H2O can be observed in the spectra. CO was only observed at the first measuring port (100ms) with the strongest CO-signal seen during experiments with straw particles. Variations in gas concentration (CO2 and H2O) and the signal from...

  7. Ignition characteristics of coal blends in an entrained flow furnace

    Energy Technology Data Exchange (ETDEWEB)

    J. Faundez; B. Arias; F. Rubiera; A. Arenillas; X. Garcia; A.L. Gordon; J.J. Pis [Universidad de Concepcion, Concepcion (Chile)

    2007-09-15

    Ignition tests were carried out on blends of three coals of different rank - subbituminous, high volatile and low volatile bituminous - in two entrained flow reactors. The ignition temperatures were determined from the gas evolution profiles (CO, CO{sub 2}, NO, O{sub 2}), while the mechanism of ignition was elucidated from these profiles and corroborated by high-speed video recording. Under the experimental conditions of high carbon loading, clear interactive effects were observed for all the blends. Ignition of the lower rank coals (subbituminous, high volatile bituminous) enhanced the ignition of the higher rank coal (low volatile bituminous) in the blends. The ignition temperatures of the blends of the low rank coals (subbituminous-high volatile bituminous) were additive. However, for the rest of the blends the ignition temperatures were always closer to the lower rank coal in the blend. 21 refs., 8 figs.

  8. Optimization of operating parameters of hybrid vertical down-flow constructed wetland systems for domestic sewerage treatment.

    Science.gov (United States)

    Huang, Zhujian; Zhang, Xianning; Cui, Lihua; Yu, Guangwei

    2016-09-15

    In this work, three hybrid vertical down-flow constructed wetland (HVDF-CW) systems with different compound substrates were fed with domestic sewage and their pollutants removal performance under different hydraulic loading and step-feeding ratio was investigated. The results showed that the hydraulic loading and step-feeding ratio were two crucial factors determining the removal efficiency of most pollutants, while substrate types only significantly affected the removal of COD and NH4(+)-N. Generally, the lower the hydraulic loading, the better removal efficiency of all contaminants, except for TN. By contrast, the increase of step-feeding ratio would slightly reduce the removal rate of ammonium and TP but obviously promoted the TN removal. Therefore, the optimal operation of this CWs could be achieved with low hydraulic loading combined with 50% of step-feeding ratio when TN removal is the priority, whereas medium or low hydraulic loading without step-feeding would be suitable when TN removal is not taken into consideration. The obtained results in this study can provide us with a guideline for design and optimization of hybrid vertical flow constructed wetland systems to improve the pollutants removal from domestic sewage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Dissolved methane oxidation and competition for oxygen in down-flow hanging sponge reactor for post-treatment of anaerobic wastewater treatment

    OpenAIRE

    Hatamoto, Masashi; Miyauchi, Tomo; Kindaichi, Tomonori; Ozaki, Noriatsu; Ohashi, Akiyoshi

    2011-01-01

    Post-treatment of anaerobic wastewater was undertaken to biologically oxidize dissolved methane, with the aim of preventing methane emission. The performance of dissolved methane oxidation and competition for oxygen among methane, ammonium, organic matter, and sulfide oxidizing bacteria were investigated using a lab-scale closed-type down-flow hanging sponge (OHS) reactor. Under the oxygen abundant condition of a hydraulic retention time of 2 h and volumetric air supply rate of 12.95 m(3)-air...

  10. Droplet behavior analysis in consideration of droplet entrainment from liquid film in annular dispersed flow

    International Nuclear Information System (INIS)

    Matsuura, Keizo; Otake, Hiroshi; Kataoka, Isao; Serizawa, Akimi

    2000-01-01

    A method of droplet behavior simulation in an annular dispersed flow has been developed. In this method, both droplet deposition and entrainment from liquid film are considered. The Lagrangian method and stochastic model are used to analyze droplet diffusion and deposition behavior in a turbulent flow, and droplet entrainment from liquid film is calculated by an entrainment correlation. For the verification of this method, Gill's experiment is analyzed, in which the transition from annular flow with no entrainment to equilibrium annular dispersed flow was observed. Analysis results can also show the similar transition tendency. The experimental results of radial distribution of droplet mass flux are compared with analysis results. The agreement is good for low liquid flow rate, but entrainment rate must be adjusted for high liquid flow rate, in which gas turbulence is thought to be modified by high droplet density. In future work the effect of high droplet density on turbulence should be considered. (author)

  11. Entrainment in Laboratory Simulations of Cumulus Cloud Flows

    Science.gov (United States)

    Narasimha, R.; Diwan, S.; Subrahmanyam, D.; Sreenivas, K. R.; Bhat, G. S.

    2010-12-01

    A variety of cumulus cloud flows, including congestus (both shallow bubble and tall tower types), mediocris and fractus have been generated in a water tank by simulating the release of latent heat in real clouds. The simulation is achieved through ohmic heating, injected volumetrically into the flow by applying suitable voltages between diametral cross-sections of starting jets and plumes of electrically conducting fluid (acidified water). Dynamical similarity between atmospheric and laboratory cloud flows is achieved by duplicating values of an appropriate non-dimensional heat release number. Velocity measurements, made by laser instrumentation, show that the Taylor entrainment coefficient generally increases just above the level of commencement of heat injection (corresponding to condensation level in the real cloud). Subsequently the coefficient reaches a maximum before declining to the very low values that characterize tall cumulus towers. The experiments also simulate the protected core of real clouds. Cumulus Congestus : Atmospheric cloud (left), simulated laboratory cloud (right). Panels below show respectively total heat injected and vertical profile of heating in the laboratory cloud.

  12. Anaerobic digestion of corn ethanol thin stillage in batch and by high-rate down-flow fixed film reactors.

    Science.gov (United States)

    Wilkinson, A; Kennedy, K J

    2012-01-01

    Thin stillage (CTS) from a dry-grind corn ethanol plant was evaluated as a carbon source for anaerobic digestion (AD) by batch and high rate semi-continuous down-flow stationary fixed film (DSFF) reactors. Biochemical methane potential (BMP) assays were carried out with CTS concentrations ranging from approximately 2,460-27,172 mg total chemical oxygen demand (TCOD) per litre, achieved by diluting CTS with clean water or a combination of clean water and treated effluent. High TCOD, SCOD and volatile solids (VS) removal efficiencies of 85 ± 2, 94 ± 0 and 82 ± 1% were achieved for CTS diluted with only clean water at an organic concentration of 21,177 mg TCOD per litre, with a methane yield of 0.30 L methane per gram TCOD(removed) at standard temperature and pressure (STP, 0 °C and 1 atmosphere). Batch studies investigating the use of treated effluent for dilution showed promising results. Continuous studies employed two mesophilic DSFF anaerobic digesters treating thin stillage, operated at hydraulic retention times (HRT) of 20, 14.3, 8.7, 6.3, 5 and 4.2 d. Successful digestion was achieved up to an organic loading rate (OLR) of approximately 7.4 g TCOD L(-1)d(-1) at a 5 d HRT with a yield of 2.05 LCH(4) L(-1)d(-1) (at STP) and TCOD and VS removal efficiencies of 89 ± 3 and 85 ± 3%, respectively.

  13. Biological oxidation of dissolved methane in effluents from anaerobic reactors using a down-flow hanging sponge reactor.

    Science.gov (United States)

    Hatamoto, Masashi; Yamamoto, Hiroki; Kindaichi, Tomonori; Ozaki, Noriatsu; Ohashi, Akiyoshi

    2010-03-01

    Anaerobic wastewater treatment plants discharge dissolved methane, which is usually not recovered. To prevent emission of methane, which is a greenhouse gas, we utilized an encapsulated down-flow hanging sponge reactor as a post-treatment to biologically oxidize dissolved methane. Within 3 weeks after reactor start-up, methane removal efficiency of up to 95% was achieved with a methane removal rate of 0.8 kg COD m(-3) day(-1) at an HRT of 2 h. After increasing the methane-loading rate, the maximum methane removal rate reached 2.2 kg COD m(-3) day(-1) at an HRT of 0.5 h. On the other hand, only about 10% of influent ammonium was oxidized to nitrate during the first period, but as airflow was increased to 2.5 L day(-1), nitrification efficiency increased to approximately 70%. However, the ammonia oxidation rate then decreased with an increase in the methane-loading rate. These results indicate that methane oxidation occurred preferentially over ammonium oxidation in the reactor. Cloning of the 16S rRNA and pmoA genes as well as phylogenetic and T-RFLP analyses revealed that type I methanotrophs were the dominant methane oxidizers, whereas type II methanotrophs were detected only in minor portion of the reactor. Copyright 2009 Elsevier Ltd. All rights reserved.

  14. Bacterial community involved in the nitrogen cycle in a down-flow sponge-based trickling filter treating UASB effluent.

    Science.gov (United States)

    Mac Conell, E F A; Almeida, P G S; Martins, K E L; Araújo, J C; Chernicharo, C A L

    2015-01-01

    The bacterial community composition of a down-flow sponge-based trickling filter treating upflow anaerobic sludge blanket (UASB) effluent was investigated by pyrosequencing. Bacterial community composition considerably changed along the reactor and over the operational period. The dominant phyla detected were Proteobacteria, Verrucomicrobia, and Planctomycetes. The abundance of denitrifiers decreased from the top to the bottom and it was consistent with the organic matter concentration gradients. At lower loadings (organic and nitrogen loading rates), the abundance of anammox bacteria was higher than that of the ammonium-oxidizing bacteria in the upper portion of the reactor, suggesting that aerobic and anaerobic ammonium oxidation occurred. Nitrification occurred in all the compartments, while anammox bacteria prominently appeared even in the presence of high organic carbon to ammonia ratios (around 1.0-2.0 gCOD gN(-1)). The results suggest that denitrifiers, nitrifiers, and anammox bacteria coexisted in the reactor; thus, different metabolic pathways were involved in ammonium removal in the post-UASB reactor sponge-based.

  15. Kinematics of flow and sediment particles at entrainment and deposition

    Science.gov (United States)

    Antico, Federica; Sanches, Pedro; Aleixo, Rui; Ferreira, Rui M. L.

    2015-04-01

    A cohesionless granular bed subjected to a turbulent open-channel flow is analysed. The key objective is to clarify the kinematics of entrainment and deposition of individual sediment particles. In particular, we quantify a) the turbulent flow field in the vicinity of particles at the instants of their entrainment and of their deposition; b) the initial particle velocity and the particle velocity immediately before returning to rest. The experimental work was performed at the Hydraulics Laboratory of IST-UL in a 12.5 m long, 0.405 m wide glass-walled flume recirculating water and sediment through independent circuits. The granular bed was a 4.0 m long and 2.5 cm deep reach filled with 5 mm diameter glass beads packed (with some vibration) to a void fraction of 0.356, typical of random packing. Upstream the mobile bed reach the bed was composed of glued particles to ensure the development of a boundary layer with the same roughness. Laboratory tests were run under conditions of weak beadload transport with Shields parameters in the range 0.007 to 0.03. Froude numbers ranged from 0.63 to 0.95 while boundary Reynolds numbers were in the range 130 to 300. It was observed that the bed featured patches of regular arrangements: face centered cubic (fcc) or hexagonal close packing (hcp) blocks alternate with and body centered cubic (bcc) blocks. The resulting bed surface exhibits cleavage lines between blocks and there are spatial variations of bed elevation. The option for artificial sediment allowed for a simplified description of particle positioning at the instant of entrainment. In particular support and pivoting angles are found analytically. Skin friction angles were determind experimentally. The only relevant variables are exposure (defined as the ratio of the actual frontal projection of the exposed area to the area of a circle with 5 mm diameter) and protrusion (defined as the vertical distance between the apex of the particle and the mean local bed elevation

  16. Entrainment and deposition rates of droplets in annular two-phase flow

    International Nuclear Information System (INIS)

    Kataoka, I.; Ishii, M.

    1986-01-01

    The droplet entrainment from a liquid film is important to the mass, momentum, and energy transfer process in annular two-phase flow. For example, the amount of entrainment as well as the rate of entrainment significantly affect the occurrences of the dryout, whereas the post-CHF heat transfer depends strongly on the entrainment and droplet sizes. Despite the importance of the entrainment rate, there have been no satisfactory correlations available in the literature. In view of these, correlations for entrainment rate covering both entrance region and equilibrium region were developed from a simple model in collaboration with data. Results show that the entrainment rate varies considerably in the entrainment-development region. However, at a certain distance from an inlet it attains an equilibrium value. A simple approximate correlation was obtained for the equilibrium state where entrainment rate and deposition rate becomes equal. The result indicates that the equilibrium entrainment rate is proportional to Weber number based on the hydraulic diameter of a tube. 34 references, 14 figures

  17. Trickle/pulse flow regime transition in downflow packed tower involving foaming liquids

    Directory of Open Access Journals (Sweden)

    Sodhi Vijay

    2012-01-01

    Full Text Available The most of past studies in foaming trickle bed reactors aimed at the improvement of efficiency and operational parameters leads to high economic advantages. Conventionally most of the industries rely on frequently used gas continuous flow (GCF where operational output is satisfactory but not yields efficiently as in pulsing flow (PF and foaming pulsing flow (FPF. Hydrodynamic characteristics like regime transitions are significantly influenced by foaming nature of liquid as well as gas and liquid flow rates. This study’s aim was to demonstrate experimentally the effects of liquid flow rate, gas flow rates and liquid surface tension on regime transition. These parameters were analyzed for the air-aqueous Sodium Lauryl Sulphate and air-water systems. More than 240 experiments were done to obtain the transition boundary for trickle flow (GCF to foaming pulsing flow (PF/FPF by use excessive foaming 15-60 ppm surfactant compositions. The trickle to pulse flow transition appeared at lower gas and liquid flow rates with decrease in liquid surface tension. All experimental data had been collected and drawn in the form of four different transitional plots which are compared and drawn by using flow coordinates proposed by different researchers. A prominent decrease in dynamic liquid saturation was observed especially during regime transitional change. The reactor two phase pressure evident a sharp rise to verify the regime transition shift from GCF to PF/FPF. Present study reveals, the regime transition boundary significantly influenced by any change in hydrodynamic as well as physiochemical properties including surface tension.

  18. Theoretical study on bubble formation and flow condensation in downflow channel with horizontal gas injection

    Science.gov (United States)

    Zhu, Kang; Li, Yanzhong; Wang, Jiaojiao; Ma, Yuan; Wang, Lei; Xie, Fushou

    2018-05-01

    Bubble formation and condensation in liquid pipes occur widely in industrial systems such as cryogenic propellant feeding system. In this paper, an integrated theoretical model is established to give a comprehensive description of the bubble formation, motion and condensation process. The model is validated by numerical simulations and bubble condensation experiments from references, and good agreements are achieved. The bubble departure diameter at the orifice and the flow condensation length in the liquid channel are predicted by the model, and effects of various influencing parameters on bubble behaviors are analyzed. Prediction results indicate that the orifice diameter, the gas feeding rate, and the liquid velocity are the primary influence factors on the bubble departure diameter. The interfacial heat transfer as well as the bubble departure diameter has a direct impact on the bubble flow condensation length, which increases by 2.5 times over a system pressure range of 0.1 0.4 MPa, and decreases by 85% over a liquid subcooling range of 5 30 K. This work could be beneficial to the prediction of bubble formation and flow condensation processes and the design of cryogenic transfer pipes.

  19. Elementary theory of bed-sediment entrainment by debris flows and avalanches

    Science.gov (United States)

    Iverson, Richard M.

    2012-01-01

    Analyses of mass and momentum exchange between a debris flow or avalanche and an underlying sediment layer aid interpretations and predictions of bed-sediment entrainment rates. A preliminary analysis assesses the behavior of a Coulomb slide block that entrains bed material as it descends a uniform slope. The analysis demonstrates that the block's momentum can grow unstably, even in the presence of limited entrainment efficiency. A more-detailed, depth-integrated continuum analysis of interacting, deformable bodies identifies mechanical controls on entrainment efficiency, and shows that entrainment rates satisfy a jump condition that involves shear-traction and velocity discontinuities at the flow-bed boundary. Explicit predictions of the entrainment rateEresult from making reasonable assumptions about flow velocity profiles and boundary shear tractions. For Coulomb-friction tractions, predicted entrainment rates are sensitive to pore fluid pressures that develop in bed sediment as it is overridden. In the simplest scenario the bed sediment liquefies completely, and the entrainment-rate equation reduces toE = 2μ1gh1 cos θ(1 − λ1)/ , where θ is the slope angle, μ1 is the flow's Coulomb friction coefficient, h1 is its thickness, λ1 is its degree of liquefaction, and is its depth-averaged velocity. For values ofλ1ranging from 0.5 to 0.8, this equation predicts entrainment rates consistent with rates of 0.05 to 0.1 m/s measured in large-scale debris-flow experiments in which wet sediment beds liquefied almost completely. The propensity for bed liquefaction depends on several factors, including sediment porosity, permeability, and thickness, and rates of compression and shear deformation that occur when beds are overridden.

  20. De-entrainment on vertical elements in air droplet cross flow

    International Nuclear Information System (INIS)

    Dallman, J.C.; Kirchner, W.L.

    1980-01-01

    De-entrainment phenomena on vertical elements in air-water droplet cross flow are generated using a horizontal array of water spray nozzles and a draft-induced wind tunnel. These conditions are used to obtain experimental values of the de-entrainment efficiency of isolated elements (25.4-, 63.5-, and 101.6-mm-diam cylinders and a 76.2-mm-square tube), and of an array of 101.6-mm-diam cylinders. A flow model is developed that extrapolates the de-entrainment efficiency of isolated elements through the use of a correlation for the interference effect to predict the efficiency of large arrays of similar elements. This simple model is shown to provide a good prediction of the de-entrainment efficiency of arrays in terms of the efficiency of an isolated element

  1. Treatment of natural rubber processing wastewater using a combination system of a two-stage up-flow anaerobic sludge blanket and down-flow hanging sponge system.

    Science.gov (United States)

    Tanikawa, D; Syutsubo, K; Hatamoto, M; Fukuda, M; Takahashi, M; Choeisai, P K; Yamaguchi, T

    2016-01-01

    A pilot-scale experiment of natural rubber processing wastewater treatment was conducted using a combination system consisting of a two-stage up-flow anaerobic sludge blanket (UASB) and a down-flow hanging sponge (DHS) reactor for more than 10 months. The system achieved a chemical oxygen demand (COD) removal efficiency of 95.7% ± 1.3% at an organic loading rate of 0.8 kg COD/(m(3).d). Bacterial activity measurement of retained sludge from the UASB showed that sulfate-reducing bacteria (SRB), especially hydrogen-utilizing SRB, possessed high activity compared with methane-producing bacteria (MPB). Conversely, the acetate-utilizing activity of MPB was superior to SRB in the second stage of the reactor. The two-stage UASB-DHS system can reduce power consumption by 95% and excess sludge by 98%. In addition, it is possible to prevent emissions of greenhouse gases (GHG), such as methane, using this system. Furthermore, recovered methane from the two-stage UASB can completely cover the electricity needs for the operation of the two-stage UASB-DHS system, accounting for approximately 15% of the electricity used in the natural rubber manufacturing process.

  2. Multiphysics Simulations of Entrained Flow Gasification. Part I: Validating the Nonreacting Flow Solver and the Particle Turbulent Dispersion Model

    KAUST Repository

    Kumar, Mayank; Ghoniem, Ahmed F.

    2012-01-01

    In this two-part paper, we describe the construction, validation, and application of a multiscale model of entrained flow gasification. The accuracy of the model is demonstrated by (1) rigorously constructing and validating the key constituent

  3. Performance of entrained flow and fluidised bed biomass gasifiers on different scales

    International Nuclear Information System (INIS)

    Tremel, Alexander; Becherer, Dominik; Fendt, Sebastian; Gaderer, Matthias; Spliethoff, Hartmut

    2013-01-01

    Highlights: ► Gasification of biomass in fluidised bed and entrained flow reactors is modelled. ► The systems are evaluated for a thermal input from 10 MW to 500 MW. ► Special attention is given to the preconditioning methods for biomass. ► Fluidised bed and entrained flow gasifiers are compared in terms of efficiency and costs. - Abstract: This biomass gasification process study compares the energetic and economic efficiencies of a dual fluidised bed and an oxygen-blown entrained flow gasifier from 10 MW th to 500 MW th . While fluidised bed gasification became the most applied technology for biomass in small and medium scale facilities, entrained flow gasification technology is still used exclusively for industrial scale coal gasification. Therefore, it is analysed whether and for which capacity the entrained flow technology is an energetically and economically efficient option for the thermo-chemical conversion of biomass. Special attention is given to the pre-conditioning methods for biomass to enable the application in an entrained flow gasifier. Process chains are selected for the two gasifier types and subsequently transformed to simulation models. The simulation results show that the performance of both gasifier types is similar for the production of a pressurised product gas (2.5 MPa). The cold gas efficiency of the fluidised bed is 76–79% and about 0.5–2 percentage points higher than for the entrained flow reactor. The net efficiencies of both technologies are similar and between 64% and 71% depending on scale. The auxiliary power consumption of the entrained flow reactor is caused mainly by the air separation unit, the oxygen compression, and the fuel pulverisation, whereas the fluidised bed requires additional power mainly for gas compression. The costs for the product gas are determined as between €4.2 cent/kWh (500 MW th ) and €7.4 cent/kWh (10 MW th ) in the economic analysis of both technologies. The study indicates that the

  4. Removal of organic substances and oxidation of ammonium nitrogen by a down-flow hanging sponge (DHS) reactor under high salinity conditions.

    Science.gov (United States)

    Uemura, Shigeki; Suzuki, Saori; Abe, Kenichi; Kubota, Keiichi; Yamaguchi, Takashi; Ohashi, Akiyoshi; Takemura, Yasuyuki; Harada, Hideki

    2010-07-01

    A down-flow hanging sponge (DHS) reactor, constructed by connecting three identical treatment units in series, was fed with highly saline artificial coke-plant wastewater containing 1400 mg L(-1) of phenol in terms of chemical oxygen demand (COD) and 500 mg-NL(-1) of ammonium nitrogen. The COD was removed by the 1st unit, achieving 92% removal at an average COD loading rate of 3.0 kg-COD m(-3)d(-1) for all units, with oxidation of ammonium nitrogen occurring primarily in the two downstream units. Microbial assays of the different units of the reactor revealed greater numbers of nitrifying bacteria in the 2nd and 3rd units than in the 1st unit, corresponding with the observed ammonium oxidation pattern of the reactor. These findings suggest that a succession of microflora was successfully established along the DHS. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  5. Dissolved methane oxidation and competition for oxygen in down-flow hanging sponge reactor for post-treatment of anaerobic wastewater treatment.

    Science.gov (United States)

    Hatamoto, Masashi; Miyauchi, Tomo; Kindaichi, Tomonori; Ozaki, Noriatsu; Ohashi, Akiyoshi

    2011-11-01

    Post-treatment of anaerobic wastewater was undertaken to biologically oxidize dissolved methane, with the aim of preventing methane emission. The performance of dissolved methane oxidation and competition for oxygen among methane, ammonium, organic matter, and sulfide oxidizing bacteria were investigated using a lab-scale closed-type down-flow hanging sponge (DHS) reactor. Under the oxygen abundant condition of a hydraulic retention time of 2h and volumetric air supply rate of 12.95m(3)-airm(-3)day(-1), greater than 90% oxidation of dissolved methane, ammonium, sulfide, and organic matter was achieved. With reduction in the air supply rate, ammonium oxidation first ceased, after which methane oxidation deteriorated. Sulfide oxidation was disrupted in the final step, indicating that COD and sulfide oxidation occurred prior to methane oxidation. A microbial community analysis revealed that peculiar methanotrophic communities dominating the Methylocaldum species were formed in the DHS reactor operation. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. De-entrainment phenomena on vertical tubes in droplet cross flow. Informal report

    International Nuclear Information System (INIS)

    Dallman, J.C.; Kirchner, W.L.

    1980-04-01

    In this study, flow conditions in the upper plenum of a PWR during the reflood stage of a loss-of-coolant accident (LOCA) are simulated using water sprays and a draft-induced wind tunnel. The de-entrainment efficiencies of isolated structures are presented for a variety of air-water droplet cross flow conditions. Since droplet splashing and/or bouncing from the draining liquid film is not accounted for in classical inertial impaction theory, there is substantial disagreement between measurement and the theory. The de-entrainment efficiencies of isolated tubes are extrapolated to those of tubes in a multiple tube array, and a predictive relation is presented for the overall de-entrainment eficiency of multiple tube arrays

  7. Physical modelling of near-wall phenomena in entrained-flow coal gasifiers

    OpenAIRE

    Troiano, Maurizio

    2015-01-01

    Combustion and gasification under slagging conditions are key aspects of the design of modern entrained-flow reactors for thermal conversion of solid fuels, aimed at increasing the overall energy efficiency. In these systems, solid particles migrate toward the reactor walls, due to swirled/tangential flow induced in the reaction chamber and to turbophoresis, generating, thanks to the very high operating temperatures, a slag layer that flows along the reactor internal walls and is drained to t...

  8. Cladding motion and entrainment during loss of flow in the LMFBR

    International Nuclear Information System (INIS)

    Scale, T.J.; Eggen, D.T.

    1978-01-01

    The study that has been undertaken here is to characterize the loss of flow with appropriate dimensionless numbers such as Re, sup(p)vap/Psteel, sup(Dh/L), and to suggest a minimum Re, necessary for entrainment of simulant cladding material under transient melting. In particular, we are interested in the downward flow of vapor over an intact rod undergoing a loss of flow or loss of heat sink. (author)

  9. Construction and demolition waste: Comparison of standard up-flow column and down-flow lysimeter leaching tests

    DEFF Research Database (Denmark)

    Butera, Stefania; Hyks, Jiri; Christensen, Thomas Højlund

    2015-01-01

    Five samples of construction and demolition waste (C&DW) were investigated in order to quantify leaching of inorganic elements under percolation conditions according to two different experimental setups: standardised up-flow saturated columns (-1TS) for Al, As, Ba, Cd, Cu, DOC, Mg, Mn, Ni, P, Pb...

  10. Onset of entrainment and degree of dispersion in dual continuous horizontal oil-water flows

    Energy Technology Data Exchange (ETDEWEB)

    Al-Wahaibi, Talal [Department of Petroleum and Chemical Engineering, Sultan Qaboos University, P.O. Box 33, Al-Khoud, P.C. 123 (Oman); Angeli, Panagiota [Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

    2009-04-15

    The transition from stratified to dual continuous oil-water flow (where each phase retains its continuity but there is dispersion of one phase into the other) as well as the dispersed phase fractions in the layers of the dual continuous pattern, were studied experimentally. Transition to this pattern from stratified flow occurs when drops of one phase appear into the other (onset of entrainment). The studies were carried out in a 38 mm ID horizontal stainless steel test section using two different inlet geometries, a T- and a Y-junction. The patterns were visualized through a transparent acrylic section located at 7 m from the inlet using a high speed video camera. Phase distribution measurements in a pipe cross section were obtained just before the acrylic section with a local impedance probe and the results were used to calculate the volume fraction of each phase entrained into the other. The onset of entrainment was found to occur at lower superficial water velocities as the oil superficial velocities increased. However, the inlet geometry did not affect significantly the transition line. During dual continuous flow, the dispersion of one phase into the opposite was found to extend further away from the interface with increasing water superficial velocity for a certain oil superficial velocity. An increase in the superficial water velocity increased the entrained fraction of water in oil (E{sub w/o}) but there was no trend with the oil velocity. Similarly, an increase in the superficial oil velocity increased the fraction of oil drops in water (E{sub o/w}) but the water velocity had no clear effect. The entrainment fractions were affected by the inlet geometry, with the T-inlet resulting in higher entrainment than the Y-inlet, perhaps because of the increased mixing induced by the T-inlet. The difference between the two inlets increased as the oil and water velocities increased. (author)

  11. Post-dryout heat transfer and entrained droplet sizes at low pressure and low flow conditions

    International Nuclear Information System (INIS)

    Jeong, H.Y.; No, H.C.

    1997-01-01

    The entrainment mechanisms and the entrained droplet sizes with relation to the flow regimes are investigated. Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low. This is explained by the change of main entrainment mechanism with the change of flow regime. In bubbly or slug flow a number of tiny droplets generated from bubble burst become important in the heat transfer after dryout. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime (j g * = 0.5∼4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 25%, respectively

  12. Characterisation of vortex flow inside an entrained cavity

    Energy Technology Data Exchange (ETDEWEB)

    Rambert, A.; Elcafsi, A.; Gougat, P. [Centre National de la Recherche Scientifique, 91 - Orsay (France). Lab. d' Informatique pour la Mecanique et les Sciences de l' Ingenieur

    2000-07-01

    A number of studies have referred to the existence of a vortex cell within an urban street canyon when ambient winds aloft are perpendicular to the street. The understanding of vortex dynamics or vorticity distribution in a such configuration is of great interest. Vortex structures play an important role in the dynamics of pollutant dispersion. This configuration was simulated by the interaction between a boundary layer and a cavity. Experimental characterisation of the vortex structures evolution was developed by flow velocity measurements inside and out of the cavity. Classical methods like hot wire and laser Doppler velocimetry (LDV) display only local measurements. Particle image velocimetry (PIV) method based on the optical flow technique permitted global velocity measurements. This technique emphasis the vortex structures inside the cavity which present small scales as well as large scales related to the cavity geometry. These vortices are usually non-stationary. (orig.)

  13. Advanced One-Dimensional Entrained-Flow Gasifier Model Considering Melting Phenomenon of Ash

    Directory of Open Access Journals (Sweden)

    Jinsu Kim

    2018-04-01

    Full Text Available A one-dimensional model is developed to represent the ash-melting phenomenon, which was not considered in the previous one-dimensional (1-D entrained-flow gasifier model. We include sensible heat of slag and the fusion heat of ash in the heat balance equation. To consider the melting of ash, we propose an algorithm that calculates the energy balance for three scenarios based on temperature. We also use the composition and the thermal properties of anorthite mineral to express ash. gPROMS for differential equations is used to solve this algorithm in a simulation; the results include coal conversion, gas composition, and temperature profile. Based on the Texaco pilot plant gasifier, we validate our model. Our results show good agreement with previous experimental data. We conclude that the sensible heat of slag and the fusion heat of ash must be included in the entrained flow gasifier model.

  14. Mercury adsorption characteristics of HBr-modified fly ash in an entrained-flow reactor.

    Science.gov (United States)

    Zhang, Yongsheng; Zhao, Lilin; Guo, Ruitao; Song, Na; Wang, Jiawei; Cao, Yan; Orndorff, William; Pan, Wei-ping

    2015-07-01

    In this study, the mercury adsorption characteristics of HBr-modified fly ash in an entrained-flow reactor were investigated through thermal decomposition methods. The results show that the mercury adsorption performance of the HBr-modified fly ash was enhanced significantly. The mercury species adsorbed by unmodified fly ash were HgCl2, HgS and HgO. The mercury adsorbed by HBr-modified fly ash, in the entrained-flow reactor, existed in two forms, HgBr2 and HgO, and the HBr was the dominant factor promoting oxidation of elemental mercury in the entrained-flow reactor. In the current study, the concentration of HgBr2 and HgO in ash from the fine ash vessel was 4.6 times greater than for ash from the coarse ash vessel. The fine ash had better mercury adsorption performance than coarse ash, which is most likely due to the higher specific surface area and longer residence time. Copyright © 2015. Published by Elsevier B.V.

  15. Downflow film boiling in a rod bundle at low pressure

    International Nuclear Information System (INIS)

    Hochreiter, L.E.; Rosal, E.R.; Fayfich, R.R.

    1978-01-01

    A series of low pressure downflow film boiling heat transfer experiments were conducted in a 14-foot (4.27 m) long electrically heater rod bundle containing 336 heater rods. The resulting data was compared with the Dougall-Rohsenow dispersed flow film boiling correlation. The data was found to lie below this correlation as the quality was increased. It is believed that buoyancy effects decreased the heat transfer in downflow film boiling. (author)

  16. Characterization of sludge properties for sewage treatment in a practical-scale down-flow hanging sponge reactor: oxygen consumption and removal of organic matter, ammonium, and sulfur.

    Science.gov (United States)

    Nomoto, Naoki; Hatamoto, Masashi; Ali, Muntjeer; Jayaswal, Komal; Iguchi, Akinori; Okubo, Tsutomu; Takahashi, Masanobu; Kubota, Kengo; Tagawa, Tadashi; Uemura, Shigeki; Yamaguchi, Takashi; Harada, Hideki

    2018-02-01

    The characteristics of sludge retained in a down-flow hanging sponge reactor were investigated to provide a better understanding of the sewage treatment process in the reactor. The organic removal and sulfur oxidation conditions were found to differ between the first layer and the following three layers. It was found that 63% and 59% of the organic matter was removed in the first layer, even though the hydraulic retention time was only 0.2 h. It is thought that the organic removal resulted from aerobic and anaerobic biodegradation on the sponge medium. The sulfate concentration increased 1.5-1.9-fold in the first layer, with almost no subsequent change in the second to fourth layers. It was shown that oxidation of sulfide in the influent was completed in the first layer. The result of the oxygen uptake rate test with an ammonium nitrogen substrate suggested that the ammonium oxidation rate was affected by the condition of dissolved oxygen (DO) or oxidation-reduction potential (ORP).

  17. Defining microbial community composition and seasonal variation in a sewage treatment plant in India using a down-flow hanging sponge reactor.

    Science.gov (United States)

    Nomoto, Naoki; Hatamoto, Masashi; Hirakata, Yuga; Ali, Muntjeer; Jayaswal, Komal; Iguchi, Akinori; Okubo, Tsutomu; Takahashi, Masanobu; Kubota, Kengo; Tagawa, Tadashi; Uemura, Shigeki; Yamaguchi, Takashi; Harada, Hideki

    2018-05-01

    The characteristics of the microbial community in a practical-scale down-flow hanging sponge (DHS) reactor, high in organic matter and sulfate ion concentration, and the seasonal variation of the microbial community composition were investigated. Microorganisms related to sulfur oxidation and reduction (2-27%), as well as Leucobacter (7.50%), were abundant in the reactor. Anaerobic bacteria (27-38% in the first layer) were also in abundance and were found to contribute to the removal of organic matter from the sewage in the reactor. By comparing the Simpson index, the abundance-based coverage estimator (ACE) index, and the species composition of the microbial community across seasons (summer/dry, summer/rainy, autumn/dry, and winter/dry), the microbial community was found to change in composition only during the winter season. In addition to the estimation of seasonal variation, the difference in the microbial community composition along the axes of the DHS reactor was investigated for the first time. Although the abundance of each bacterial species differed along both axes of the reactor, the change of the community composition in the reactor was found to be greater along the vertical axis than the horizontal axis of the DHS reactor.

  18. Particle re-entrainment from a powder deposit in an horizontal air flow

    International Nuclear Information System (INIS)

    Alloul, L.; Witschger, O.; Alloul, L.; Renoux, A.; Le Dur, D.; Monnatte, J.

    2000-01-01

    Particle re-entrainment from surfaces to turbulent air flow is an important subject in many different fields like nuclear safety, environmental air pollution, sediment transport by wind, surface contamination in semiconductor operations. Theoretical and experimental studies have been numerous and cover different aspects of the phenomena. Although a number of theoretical works have been devoted for describing the mechanisms of detachment of primary spherical particles form flat smooth surfaces in a turbulent flow, experimental data are still needed in order to comparison. Moreover, the knowledge of the effect of parameters related to the deposit (monolayer, multilayer, cone-like pile), the powder particles (particle-size distribution, adhesive properties), the surface (roughness,...),the airflow (velocity, acceleration, turbulence) or the environment (humidity,...) is still in an elementary stage. The main objective of our work is to contribute to the understanding and quantification of the parameters that govern the particle re-entrainment from a powder deposit in an turbulent horizontal airflow. Therefore, a new experimental facility called BISE (french acronym for wind tunnel for studying particle re-entrainment by airflow) has been designed and built in our laboratory. (authors)

  19. Large Eddy and Interface Simulation (LEIS) of liquid entrainment in turbulent stratified flow

    International Nuclear Information System (INIS)

    Gulati, S.; Buongiorno, J.; Lakehal, D.

    2011-01-01

    Dryout of the liquid film on the fuel rods in BWR fuel assemblies leads to an abrupt decrease in heat transfer coefficient and can result in fuel failure. The process of mechanical mass transfer from the continuous liquid field into the continuous vapor field along the liquid-vapor interface is called entrainment and is the dominant depletion mechanism for the liquid film in annular flow. Using interface tracking methods combined with a Large Eddy Simulation approach, implemented in the Computational Multi-Fluid Dynamics (CMFD) code TransAT®, we are studying entrainment phenomena in BWR fuel assemblies. In this paper we report on the CMFD simulation approaches and the current validation effort for the code. (author)

  20. Effect of splash on the deposition and re-entrainment in annular mist flow

    International Nuclear Information System (INIS)

    Xie, Heng; Koshizuka, Seiichi; Oka, Yoshiaki

    2004-01-01

    The three-dimensional Moving Particle Semi-implicit (MPS) method is employed to simulate the deposition process of single droplet on the liquid film. The model accounts for the presence of inertial, gravitation, viscous and surface tension and is validated by comparison with experiment results. A one-dimensional mixture model is developed to calculate the necessary parameters for the simulation of deposition on the Boiling Water Reactor (BWR) condition. The correlations and methods on void fraction, entertainment fraction and droplet velocity and size distribution are employed to get the parameters of droplet and liquid film. The simulation results are analyzed to study the effect of splash on the deposition and re-entrainment process in annular-mist flow on the condition of BWR. It is found that the splash plays an important role in the deposition and re-entrainment process in high quality conditions of BWR. (author)

  1. A review of recent developments on turbulent entrainment in stratified flows

    International Nuclear Information System (INIS)

    Cotel, Aline J

    2010-01-01

    Stratified interfaces are present in many geophysical flow situations, and transport across such an interface is an essential factor for correctly evaluating the physical processes taking place at many spatial and temporal scales in such flows. In order to accurately evaluate vertical and lateral transport occurring when a turbulent flow impinges on a stratified interface, the turbulent entrainment and vorticity generation mechanisms near the interface must be understood and quantified. Laboratory experiments were performed for three flow configurations: a vertical thermal, a sloping gravity current and a vertical turbulent jet with various tilt angles and precession speeds. All three flows impinged on an interface separating a two-layer stably stratified environment. The entrainment rate is quantified for each flow using laser-induced fluorescence and compared to predictions of Cotel and Breidenthal (1997 Appl. Sci. Res. 57 349-66). The possible applications of transport across stratified interfaces include the contribution of hydrothermal plumes to the global ocean energy budget, turbidity currents on the ocean floor, the design of lake de-stratification systems, modeling gas leaks from storage reservoirs, weather forecasting and global climate change.

  2. Electrification of particulate entrained fluid flows-Mechanisms, applications, and numerical methodology

    Science.gov (United States)

    Wei, Wei; Gu, Zhaolin

    2015-10-01

    Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas-solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The charge

  3. Entrainment effects in periodic forcing of the flow over a backward-facing step

    Science.gov (United States)

    Berk, T.; Medjnoun, T.; Ganapathisubramani, B.

    2017-07-01

    The effect of the Strouhal number on periodic forcing of the flow over a backward-facing step (height, H ) is investigated experimentally. Forcing is applied by a synthetic jet at the edge of the step at Strouhal numbers ranging from 0.21 flow. In the present study, variations with Strouhal number are explained based on a continuous variation of entrainment of momentum into the recirculation region rather than on specific frequencies. The reattachment length is shown to decrease linearly with entrainment of momentum. Vertical momentum flux is driven by vortices generated by the forcing, and locally vertical momentum flux is shown to be qualitatively similar to circulation for all cases considered. Total circulation (and therewith entrainment of momentum and the effect on the reattachment length) is shown to decrease with Strouhal number, whereas this is not predicted by models based on specific low and high frequencies. An empirical model for the (decay of) circulation is derived by tracking vortices in phase-locked data. This model is used to decipher relevant scaling parameters that explain the variations in circulation, entrainment of momentum, and reattachment length. Three regimes of Strouhal number are identified. A low-Strouhal-number regime is observed for which vortices are formed at a late stage relative to the recirculation region, causing a decrease in effectiveness. For high Strouhal numbers, vortices are being reingested into the actuator or are packed so close together that they cancel each other, both decreasing the effectiveness of forcing. In the intermediate regime a vortex train is formed of which the decay of circulation increases for increasing Strouhal number. The scaling of this

  4. Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

    International Nuclear Information System (INIS)

    Bae, Byeong Geon; Yun, Byong Jo; Kim, Kyoung Du

    2014-01-01

    It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

  5. Debris flow analysis with a one dimensional dynamic run-out model that incorporates entrained material

    Science.gov (United States)

    Luna, Byron Quan; Remaître, Alexandre; van Asch, Theo; Malet, Jean-Philippe; van Westen, Cees

    2010-05-01

    Estimating the magnitude and the intensity of rapid landslides like debris flows is fundamental to evaluate quantitatively the hazard in a specific location. Intensity varies through the travelled course of the flow and can be described by physical features such as deposited volume, velocities, height of the flow, impact forces and pressures. Dynamic run-out models are able to characterize the distribution of the material, its intensity and define the zone where the elements will experience an impact. These models can provide valuable inputs for vulnerability and risk calculations. However, most dynamic run-out models assume a constant volume during the motion of the flow, ignoring the important role of material entrained along its path. Consequently, they neglect that the increase of volume enhances the mobility of the flow and can significantly influence the size of the potential impact area. An appropriate erosion mechanism needs to be established in the analyses of debris flows that will improve the results of dynamic modeling and consequently the quantitative evaluation of risk. The objective is to present and test a simple 1D debris flow model with a material entrainment concept based on limit equilibrium considerations and the generation of excess pore water pressure through undrained loading of the in situ bed material. The debris flow propagation model is based on a one dimensional finite difference solution of a depth-averaged form of the Navier-Stokes equations of fluid motions. The flow is treated as a laminar one phase material, which behavior is controlled by a visco-plastic Coulomb-Bingham rheology. The model parameters are evaluated and the model performance is tested on a debris flow event that occurred in 2003 in the Faucon torrent (Southern French Alps).

  6. Evaluation of the process performance of a down-flow hanging sponge reactor for direct treatment of domestic wastewater in Bangkok, Thailand.

    Science.gov (United States)

    Miyaoka, Yuma; Yoochatchaval, Wilasinee; Sumino, Haruhiko; Banjongproo, Pathan; Yamaguchi, Takashi; Onodera, Takashi; Okadera, Tomohiro; Syutsubo, Kazuaki

    2017-08-24

    This study assesses the performance of an aerobic trickling filter, down-flow hanging sponge (DHS) reactor, as a decentralized domestic wastewater treatment technology. Also, the characteristic eukaryotic community structure in DHS reactor was investigated. Long-term operation of a DHS reactor for direct treatment of domestic wastewater (COD = 150-170 mg/L and BOD = 60-90 mg/L) was performed under the average ambient temperature ranged from 28°C to 31°C in Bangkok, Thailand. Throughout the evaluation period of 550 days, the DHS reactor at a hydraulic retention time of 3 h showed better performance than the existing oxidation ditch process in the removal of organic carbon (COD removal rate = 80-83% and BOD removal rate = 91%), nitrogen compounds (total nitrogen removal rate = 45-51% and NH 4 + -N removal rate = 95-98%), and low excess sludge production (0.04 gTS/gCOD removed). The clone library based on the 18S ribosomal ribonucleic acid gene sequence revealed that phylogenetic diversity of 18S rRNA gene in the DHS reactor was higher than that of the present oxidation ditch process. Furthermore, the DHS reactor also demonstrated sufficient COD and NH 4 + -N removal efficiency under flow rate fluctuation conditions that simulates a small-scale treatment facility. The results show that a DHS reactor could be applied as a decentralized domestic wastewater treatment technology in tropical regions such as Bangkok, Thailand.

  7. Microbial community composition of a down-flow hanging sponge (DHS) reactor combined with an up-flow anaerobic sludge blanket (UASB) reactor for the treatment of municipal sewage.

    Science.gov (United States)

    Kubota, Kengo; Hayashi, Mikio; Matsunaga, Kengo; Iguchi, Akinori; Ohashi, Akiyoshi; Li, Yu-You; Yamaguchi, Takashi; Harada, Hideki

    2014-01-01

    The microbial community composition of a down-flow hanging sponge (DHS) reactor in an up-flow anaerobic sludge blanket (UASB)-DHS system used for the treatment of municipal sewage was investigated. The clone libraries showed marked differences in microbial community composition at different reactor heights and in different seasons. The dominant phylotypes residing in the upper part of the reactor were likely responsible for removing organic matters because a significant reduction in organic matter in the upper part was observed. Quantification of the amoA genes revealed that the proportions of ammonia oxidizing bacteria (AOB) varied along the vertical length of the reactor, with more AOB colonizing the middle and lower parts of the reactor than the top of the reactor. The findings indicated that sewage treatment was achieved by a separation of microbial habitats responsible for organic matter removal and nitrification in the DHS reactor. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Product Characterization for Entrained Flow Coal/Biomass Co-Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Maghzi, Shawn; Subramanian, Ramanathan; Rizeq, George; Singh, Surinder; McDermott, John; Eiteneer, Boris; Ladd, David; Vazquez, Arturo; Anderson, Denise; Bates, Noel

    2011-09-30

    The U.S. Department of Energy‘s National Energy Technology Laboratory (DOE NETL) is exploring affordable technologies and processes to convert domestic coal and biomass resources to high-quality liquid hydrocarbon fuels. This interest is primarily motivated by the need to increase energy security and reduce greenhouse gas emissions in the United States. Gasification technologies represent clean, flexible and efficient conversion pathways to utilize coal and biomass resources. Substantial experience and knowledge had been developed worldwide on gasification of either coal or biomass. However, reliable data on effects of blending various biomass fuels with coal during gasification process and resulting syngas composition are lacking. In this project, GE Global Research performed a complete characterization of the gas, liquid and solid products that result from the co-gasification of coal/biomass mixtures. This work was performed using a bench-scale gasifier (BSG) and a pilot-scale entrained flow gasifier (EFG). This project focused on comprehensive characterization of the products from gasifying coal/biomass mixtures in a high-temperature, high-pressure entrained flow gasifier. Results from this project provide guidance on appropriate gas clean-up systems and optimization of operating parameters needed to develop and commercialize gasification technologies. GE‘s bench-scale test facility provided the bulk of high-fidelity quantitative data under temperature, heating rate, and residence time conditions closely matching those of commercial oxygen-blown entrained flow gasifiers. Energy and Environmental Research Center (EERC) pilot-scale test facility provided focused high temperature and pressure tests at entrained flow gasifier conditions. Accurate matching of syngas time-temperature history during cooling ensured that complex species interactions including homogeneous and heterogeneous processes such as particle nucleation, coagulation, surface condensation, and

  9. Product Characterization for Entrained Flow Coal/Biomass Co-Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Maghzi, Shawn [General Electric Global Research, Niskayuna, NY (United States); Subramanian, Ramanathan [General Electric Global Research, Niskayuna, NY (United States); Rizeq, George [General Electric Global Research, Niskayuna, NY (United States); Singh, Surinder [General Electric Global Research, Niskayuna, NY (United States); McDermott, John [General Electric Global Research, Niskayuna, NY (United States); Eiteneer, Boris [General Electric Global Research, Niskayuna, NY (United States); Ladd, David [General Electric Global Research, Niskayuna, NY (United States); Vazquez, Arturo [General Electric Global Research, Niskayuna, NY (United States); Anderson, Denise [General Electric Global Research, Niskayuna, NY (United States); Bates, Noel [General Electric Global Research, Niskayuna, NY (United States)

    2011-12-11

    The U.S. Department of Energy's National Energy Technology Laboratory (DOE NETL) is exploring affordable technologies and processes to convert domestic coal and biomass resources to high-quality liquid hydrocarbon fuels. This interest is primarily motivated by the need to increase energy security and reduce greenhouse gas emissions in the United States. Gasification technologies represent clean, flexible and efficient conversion pathways to utilize coal and biomass resources. Substantial experience and knowledge had been developed worldwide on gasification of either coal or biomass. However, reliable data on effects of blending various biomass fuels with coal during gasification process and resulting syngas composition are lacking. In this project, GE Global Research performed a complete characterization of the gas, liquid and solid products that result from the co-gasification of coal/biomass mixtures. This work was performed using a bench-scale gasifier (BSG) and a pilot-scale entrained flow gasifier (EFG). This project focused on comprehensive characterization of the products from gasifying coal/biomass mixtures in a high-temperature, high-pressure entrained flow gasifier. Results from this project provide guidance on appropriate gas clean-up systems and optimization of operating parameters needed to develop and commercialize gasification technologies. GE's bench-scale test facility provided the bulk of high-fidelity quantitative data under temperature, heating rate, and residence time conditions closely matching those of commercial oxygen-blown entrained flow gasifiers. Energy and Environmental Research Center (EERC) pilot-scale test facility provided focused high temperature and pressure tests at entrained flow gasifier conditions. Accurate matching of syngas time-temperature history during cooling ensured that complex species interactions including homogeneous and heterogeneous processes such as particle nucleation, coagulation, surface condensation

  10. K-capture by Al-Si based Additives in an Entrained Flow Reactor

    DEFF Research Database (Denmark)

    Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao

    2016-01-01

    A water slurry, consisting of KCl and Al-Si based additives (kaolin and coal fly ash) was fed into an entrained flow reactor (EFR) to study the K-capturing reaction of the additives at suspension-fired conditions. Solid products collected from the reactor were analysed with respect to total...... of KCl to K-aluminosilicate decreased. When reaction temperature increased from 1100 °C to 1450 °C, the conversion of KCl does not change significantly, which differs from the trend observed in fixed-bed reactor....

  11. Development of a Cl-impregnated activated carbon for entrained-flow capture of elemental mercury.

    Science.gov (United States)

    Ghorishi, S Behrooz; Keeney, Robert M; Serre, Shannon D; Gullett, Brian K; Jozewicz, Wojciech S

    2002-10-15

    Efforts to discern the role of an activated carbon's surface functional groups on the adsorption of elemental mercury (Hg0) and mercuric chloride demonstrated that chlorine (Cl) impregnation of a virgin activated carbon using dilute solutions of hydrogen chloride leads to increases (by a factor of 2-3) in fixed-bed capture of these mercury species. A commercially available activated carbon (DARCO FGD, NORITAmericas Inc. [FGD])was Cl-impregnated (Cl-FGD) [5 lb (2.3 kg) per batch] and tested for entrained-flow, short-time-scale capture of Hg0. In an entrained flow reactor, the Cl-FGD was introduced in Hg0-laden flue gases (86 ppb of Hg0) of varied compositions with gas/solid contact times of about 3-4 s, resulting in significant Hg0 removal (80-90%), compared to virgin FGD (10-15%). These levels of Hg0 removal were observed across a wide range of very low carbon-to-mercury weight ratios (1000-5000). Variation of the natural gas combustion flue gas composition, by doping with nitrogen oxides and sulfur dioxide, and the flow reactor temperature (100-200 degrees C) had minimal effects on Hg0 removal bythe Cl-FGD in these carbon-to-mercury weight ratios. These results demonstrate significant enhancement of activated carbon reactivity with minimal treatment and are applicable to combustion facilities equipped with downstream particulate matter removal such as an electrostatic precipitator.

  12. Improved Accuracy for Two-Phase Downflow Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Cliff B. Davis

    2012-10-01

    Problems have been reported for very high downflows in small and intermediate pipes in the bubbly and slug flow regimes. When the flow rate is near critical, the calculated mass flow rate depends strongly on the flow orientation for small and intermediate pipes, whereas the flow rate is nearly independent of flow direction for large pipes. At very high flow rates, the flow is expected to be nearly homogenous and hence to be nearly independent of flow direction. The flow rates calculated by RELAP5-3D agree with this expectation except for downflow in small and intermediate pipes, where the calculated flows in the downward direction are about 20% lower than the flows in the upward and horizontal directions. The problem was traced to an extrapolation of the EPRI drift flux correlation beyond the range of its database. The problem was corrected by creating a very high downflow regime. The EPRI correlation is replaced by the Zuber-Findlay churn turbulent and Kataoka-Ishii drift flux correlations in the very high downflow regime for small and intermediate pipes.

  13. Sugarcane molasses-based bio-ethanol wastewater treatment by two-phase multi-staged up-flow anaerobic sludge blanket (UASB) combination with up-flow UASB and down-flow hanging sponge.

    Science.gov (United States)

    Choeisai, P; Jitkam, N; Silapanoraset, K; Yubolsai, C; Yoochatchaval, W; Yamaguchi, T; Onodera, T; Syutsubo, K

    2014-01-01

    This study was designed to evaluate a treatment system for high strength wastewater (vinasse) from a sugarcane molasses-based bio-ethanol plant in Thailand. A laboratory-scale two-phase treatment system composed of a sulfate reducing (SR) tank and multi-staged up-flow anaerobic sludge blanket (MS-UASB) reactor was used as the pre-treatment unit. Conventional UASB and down-flow hanging sponge (DHS) reactors were used as the post-treatment unit. The treatment system was operated for 300 days under ambient temperature conditions (24.6-29.6 °C). The hydraulic retention time (HRT) in each unit was kept at 25 h for the two-phase system and 23 h for the UASB&DHS. The influent concentration was allowed to reach up to 15,000 mg chemical oxygen demand (COD)/L. COD removal efficiency (based on influent COD) of the two-phase MS-UASB and the UASB&DHS was 54.9 and 18.7%, respectively. Due to the effective removal of sulfide in the SR tank, the MS-UASB achieved a high methane conversion ratio of up to 97%. In DHS, nitrification occurred at the outside portion of the sponge media while denitrification occurred at the inside. Consequently, 27% of the total nitrogen (TN) was removed. An amount of 32% of residual nitrogen (28 mgN/L) was in the form of nitrate, a better nitrogen state for fertilizer.

  14. Effect of Entrainment and Overflow Occurrences on Concentration Profile in PUREX Flow Sheet

    International Nuclear Information System (INIS)

    Ueda, Yoshinori; Ishii, Junichi; Matsumoto, Shiro

    2003-01-01

    A deviation in the operational condition of a mixer settler and a centrifugal contactor causes an entrainment or an overflow, which affects the concentration profile. Although there has been no quantitative study about the effect of such abnormal flows on the concentration profile, the occurrence of such abnormal flows has been severely restricted for a PUREX flow sheet. However, the restriction of abnormal flows can be relaxed when the effect of such flows is limited within the allowable range such that the concentration of the product does not deviate from its specification. This relaxation could serve to benefit a continuous operation under a certain degree of deviation from the operational condition and a smaller design load of a solvent extractor. From this viewpoint, the relationship between the magnitude of abnormal flows and the effect of them on the process was studied quantitatively using a specially developed code in a wide range of PUREX flow sheet conditions, and the possibility of this relaxation was investigated. The results showed that the effect of the abnormal flow on the concentration in the organic outflow or aqueous raffinate was dominated by the leakage fraction under normal conditions regardless of each specific flow sheet condition. The common correlations were found between the leakage fraction of uranium and plutonium under the occurrence of abnormal flows and that under no abnormal flow for the stripping and extracting conditions, respectively. Comparing the given correlations and the usual specification of the leakage fraction of uranium and plutonium suggested that the restriction of the abnormal flows could be relaxed for a usual PUREX flow sheet

  15. Influence of bed material entrainment and non-Newtonian rheology on turbulent geophysical flows dynamics. Numerical study

    Science.gov (United States)

    Eglit, M. E.; Yakubenko, A. E.; Yakubenko, T. A.

    2017-10-01

    This paper deals with the mathematical and numerical modeling of the propagation stage of geophysical gravity-driven flows, such as snow avalanches, mudflows, and rapid landslides. New mathematical models are presented which are based on full, not-depth-averaged equations of mechanics of continuous media. The models account for three important issues: non-Newtonian rheology of the moving material, entrainment of the bed material by the flow, and turbulence. The main objective is to investigate the effect of these three factors on the flow dynamics and on the value of the entrainment rate. To exclude the influence of many other factors, e.g., the complicated slope topography, only the motion down a long uniform slope with a constant inclination angle is studied numerically. Moreover, the entire flow from the front to the rear area was not modeled, but only its middle part where the flow is approximately uniform in length. One of the qualitative results is that in motion along homogeneous slope the mass entrainment increases the flow velocity and depth while the entrainment rate at large time tends to become constant which depends on the physical properties of the flow and the underlying material but not on the current values of the flow velocity and depth.

  16. Dynamic modeling of Shell entrained flow gasifier in an integrated gasification combined cycle process

    International Nuclear Information System (INIS)

    Lee, Hyeon-Hui; Lee, Jae-Chul; Joo, Yong-Jin; Oh, Min; Lee, Chang-Ha

    2014-01-01

    Highlights: • Detailed dynamic model for the Shell entrained flow gasifier was developed. • The model included sub-models of reactor, membrane wall, gas quench and slag flow. • The dynamics of each zone including membrane wall in the gasifier were analyzed. • Cold gas efficiency (81.82%), gas fraction and temperature agreed with Shell data. • The model could be used as part of the overall IGCC simulation. - Abstract: The Shell coal gasification system is a single-stage, up-flow, oxygen-blown gasifier which utilizes dry pulverized coal with an entrained flow mechanism. Moreover, it has a membrane wall structure and operates in the slagging mode. This work provides a detailed dynamic model of the 300 MW Shell gasifier developed for use as part of an overall IGCC (integrated gasification combined cycle) process simulation. The model consists of several sub-models, such as a volatilization zone, reaction zone, quench zone, slag zone, and membrane wall zone, including heat transfers between the wall layers and steam generation. The dynamic results were illustrated and the validation of the gasifier model was confirmed by comparing the results in the steady state with the reference data. The product gases (H 2 and CO) began to come out from the exit of the reaction zone within 0.5 s, and nucleate boiling heat transfer was dominant in the water zone of the membrane wall due to high heat fluxes. The steady state of the process was reached at nearly t = 500 s, and our simulation data for the steady state, such as the temperature and composition of the syngas, the cold gas efficiency (81.82%), and carbon conversion (near 1.0) were in good agreement with the reference data

  17. Study on CFD approach for gas entrainment phenomenon. Evaluation of applicability of finite element flow analysis

    International Nuclear Information System (INIS)

    Eguchi, Yuzuru

    2005-07-01

    The report is concerned with the evaluation of applicability of numerical modelling methods for the prediction of gas entrainment in an upper plenum of a sodium-cooled fast breeder reactor (FBR). Special attention was paid to applicability of variational multiscale (VMS) modelling in the context of the Finite Element Method. Two flow problems, which were experimentally shown to induce gas entrainment, are solved by a VMS code (MISTRAL). First, computing a benchmark problem of a gas entrainment swirl flow in a cylindrical vessel has led to the following results; (1) the VMS solution is able to resolve the precise vortex core structure more accurately than the non-VMS solution computed by Smart-fem. The circumferential velocity obtained from VMS computation rises almost double in comparison with the non-VMS solution, though it still underestimates the experimental values. (2) the half-value radius of the negative region of the second invariant of velocity gradient matches well between the VMS solution and non-VMS solution. (3) the negative/positive boundary of the second invariant of velocity gradient obtained from the VMS solution is closer to the vortex core radius observed in the experiment than that of the non-VMS solution, though the vortex dip length computed from the VMS result is shorter than the experimental value. Second, computing a benchmark problem of open channel flow with a square pillar and downstream suction pipe has led to the following results; (4) 2Δx-type spatial oscillation was observed due to lack of mesh subdivisions. (5) the distributional profile of the second invariant of velocity gradient is similar to that of the first problem (swirl flow in a cylindrical vessel), characterized by a strong negative region surrounded by a weak positive region. As a possible future plan, it may be necessary to analyze more precisely the features of unsteady vortices obtained in the second benchmark problem and to identify the difference (if any) from the

  18. Flash pyrolysis of agricultural residues using a plasma heated laminar entrained flow reactor

    International Nuclear Information System (INIS)

    Xiu Shuangning; Yi Weiming; Li Baoming

    2005-01-01

    In order to study the volatilization characteristics of biomass particles at flash heating rates, a plasma heated laminar entrained flow reactor (PHLEFR) was designed and built in our lab. Two agricultural residues, wheat straw and corn stalk, were chosen as feedstock for pyrolysis which were conducted on the PHLEFR with the aim of determining the extent of thermal decomposition at high heating rate (more than 10 4o Cs -1 ). Based on the experimental data, a first order kinetic model was introduced and the relevant kinetic parameters (apparent active energy and apparent frequency factor) were determined for the two straws: E=31.51kJmol -1 , A=1028s -1 (wheat straw) and E=33.74kJmol -1 , A=1013s -1 (corn stalk). The predicted conversion of the fitted model to the experimental data provided general agreements when one considered the experimental errors

  19. Development of advanced air-blown entrained-flow two-stage bituminous coal IGCC gasifier

    Directory of Open Access Journals (Sweden)

    Abaimov Nikolay A.

    2017-01-01

    Full Text Available Integrated gasification combined cycle (IGCC technology has two main advantages: high efficiency, and low levels of harmful emissions. Key element of IGCC is gasifier, which converts solid fuel into a combustible synthesis gas. One of the most promising gasifiers is air-blown entrained-flow two-stage bituminous coal gasifier developed by Mitsubishi Heavy Industries (MHI. The most obvious way to develop advanced gasifier is improvement of commercial-scale 1700 t/d MHI gasifier using the computational fluid dynamics (CFD method. Modernization of commercial-scale 1700 t/d MHI gasifier is made by changing the regime parameters in order to improve its cold gas efficiency (CGE and environmental performance, namely H2/CO ratio. The first change is supply of high temperature (900°C steam in gasifier second stage. And the second change is additional heating of blast air to 900°C.

  20. Multiphysics Simulations of Entrained Flow Gasification. Part I: Validating the Nonreacting Flow Solver and the Particle Turbulent Dispersion Model

    KAUST Repository

    Kumar, Mayank

    2012-01-19

    In this two-part paper, we describe the construction, validation, and application of a multiscale model of entrained flow gasification. The accuracy of the model is demonstrated by (1) rigorously constructing and validating the key constituent submodels against relevant canonical test cases from the literature and (2) validating the integrated model against experimental data from laboratory scale and commercial scale gasifiers. In part I, the flow solver and particle turbulent dispersion models are validated against experimental data from nonswirling flow and swirling flow test cases in an axisymmetric sudden expansion geometry and a two-phase flow test case in a cylindrical bluff body geometry. Results show that while the large eddy simulation (LES) performs best among all tested models in predicting both swirling and nonswirling flows, the shear stress transport (SST) k-ω model is the best choice among the commonly used Reynolds-averaged Navier-Stokes (RANS) models. The particle turbulent dispersion model is accurate enough in predicting particle trajectories in complex turbulent flows when the underlying turbulent flow is well predicted. Moreover, a commonly used modeling constant in the particle dispersion model is optimized on the basis of comparisons with particle-phase experimental data for the two-phase flow bluff body case. © 2011 American Chemical Society.

  1. STUDY OF MERCURY OXIDATION BY SCR CATALYST IN AN ENTRAINED-FLOW REACTOR UNDER SIMULATED PRB CONDITIONS

    Science.gov (United States)

    A bench-scale entrained-flow reactor system was constructed for studying elemental mercury oxidation under selective catalytic reduction (SCR) reaction conditions. Simulated flue gas was doped with fly ash collected from a subbituminous Powder River Basin (PRB) coal-fired boiler ...

  2. Distinguishing Between Supra-Arcade Downflows and Plasmoids

    Science.gov (United States)

    Savage, Sabrina

    2015-01-01

    Supra-arcade downflows (SADs) and downflowing loops (SADLs), observed as sunward-traveling voids and thin flux tubes in the current sheet region above developing flare arcades, are considered indicators of magnetic reconnection fueling long­-duration solar eruptions. These flows are located in regions of very low signal-­to-noise in the corona where high cadence magnetic field measurements are not yet achievable, making observations difficult to fully interpret with respect to reconnection. Several models have been developed to explain their characteristics and behaviors, but most do not successfully recreate the observations. We will present a variety of downflow observations and provide comparisons to a number of the more prominent models.

  3. Supercavitating flow around high-speed underwater projectile near free surface induced by air entrainment

    Directory of Open Access Journals (Sweden)

    Chang Xu

    2018-03-01

    Full Text Available Cavitating flow near free surface is a complicated issue and may provide new inspiration on high-speed surface cruising. This study observes stable supercavitating flow as a new phenomenon in a launch experiment of axisymmetric projectile when the upper side of the projectile coincides with the free surface. A numerical approach is established using large eddy-simulation and volume-of-fluid methods, and good agreements are achieved between numerical and experimental results. Supercavity formation mechanism is revealed by analyzing the experiment photographs and the iso-surface of 90% water volume fraction in numerical results. The entrainment of a large amount of air into the cavity can cause the pressure inside the cavity to similarly increase with the pressure outside the cavity, which makes the actual cavitation number close to zero and is similar to supercavitation. Cases with various headforms of the projectile and cavitation numbers on the cavitating flow, as well as the drag reduction effects are further examined. Results indicate that the present strategy near the free surface could possibly be a new effective approach for high-speed cruising after vigorous design optimization in the future.

  4. Performance evaluation of mobile downflow booths for reducing airborne particles in the workplace.

    Science.gov (United States)

    Lo, Li-Ming; Hocker, Braden; Steltz, Austin E; Kremer, John; Feng, H Amy

    2017-11-01

    Compared to other common control measures, the downflow booth is a costly engineering control used to contain airborne dust or particles. The downflow booth provides unidirectional filtered airflow from the ceiling, entraining released particles away from the workers' breathing zone, and delivers contained airflow to a lower level exhaust for removing particulates by filtering media. In this study, we designed and built a mobile downflow booth that is capable of quick assembly and easy size change to provide greater flexibility and particle control for various manufacturing processes or tasks. An experimental study was conducted to thoroughly evaluate the control performance of downflow booths used for removing airborne particles generated by the transfer of powdered lactose between two containers. Statistical analysis compared particle reduction ratios obtained from various test conditions including booth size (short, regular, or extended), supply air velocity (0.41 and 0.51 m/s or 80 and 100 feet per minute, fpm), powder transfer location (near or far from the booth exhaust), and inclusion or exclusion of curtains at the booth entrance. Our study results show that only short-depth downflow booths failed to protect the worker performing powder transfer far from the booth exhausts. Statistical analysis shows that better control performance can be obtained with supply air velocity of 0.51 m/s (100 fpm) than with 0.41 m/s (80 fpm) and that use of curtains for downflow booths did not improve their control performance.

  5. Performance evaluation of the sulfur-redox-reaction-activated up-flow anaerobic sludge blanket and down-flow hanging sponge anaerobic/anoxic sequencing batch reactor system for municipal sewage treatment.

    Science.gov (United States)

    Hatamoto, Masashi; Ohtsuki, Kota; Maharjan, Namita; Ono, Shinya; Dehama, Kazuya; Sakamoto, Kenichi; Takahashi, Masanobu; Yamaguchi, Takashi

    2016-03-01

    A sulfur-redox-reaction-activated up-flow anaerobic sludge blanket (UASB) and down-flow hanging sponge (DHS) system, combined with an anaerobic/anoxic sequencing batch reactor (A2SBR), has been used for municipal sewage treatment for over 2 years. The present system achieved a removal rate of 95±14% for BOD, 74±22% for total nitrogen, and 78±25% for total phosphorus, including low water temperature conditions. Sludge conversion rates during the operational period were 0.016 and 0.218 g-VSS g-COD-removed(-1) for the UASB, and DHS, respectively, which are similar to a conventional UASB-DHS system, which is not used of sulfur-redox-reaction, for sewage treatment. Using the sulfur-redox reaction made advanced treatment of municipal wastewater with minimal sludge generation possible, even in winter. Furthermore, the occurrence of a unique phenomenon, known as the anaerobic sulfur oxidation reaction, was confirmed in the UASB reactor under the winter season. Copyright © 2016. Published by Elsevier Ltd.

  6. Numerical investigation of slag formation in an entrained-flow gasifier

    Science.gov (United States)

    Zageris, G.; Geza, V.; Jakovics, A.

    2018-05-01

    A CFD mathematical model for an entrained-flow gasifier is constructed – the model of an actual gasifier is rendered in 3D and appropriately meshed. Then, the turbulent gas flow in the gasifier is modeled with the realizable k-ε approach, taking devolatilization, combustion and coal gasification in account. Various such simulations are conducted, obtaining results for different air inlet positions and by tracking particles of varying sizes undergoing devolatilization and gasification. The model identifies potential problematic zones where most particles collide with the gasifier walls, indicating risk regions where ash deposits could most likely form. In conclusion, effects on the formation of an ash layer of air inlet positioning and particle size allowed in the main gasifier tank are discussed, and viable solutions such as radial inlet positioning for decreasing the amount of undesirable deposits are proposed. We also conclude that the particular chemical reactions that take place inside the gasifier play a significant role in determining how slagging occurs inside a gasifier.

  7. The transformation of nitrogen during pressurized entrained-flow pyrolysis of Chlorella vulgaris.

    Science.gov (United States)

    Maliutina, Kristina; Tahmasebi, Arash; Yu, Jianglong

    2018-08-01

    The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600-900 °C and pressures of 0.1-4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. Ignition behaviour of different rank coals in an entrained flow reactor

    Energy Technology Data Exchange (ETDEWEB)

    J. Faundez; A. Arenillas; F. Rubiera; X. Garcia; A.L. Gordon; J.J. Pis [Instituto Nacional del Carbon (INCAR), Oviedo (Spain)

    2005-12-01

    An experimental study to determine the temperature and mechanism of coal ignition was carried out by using an entrained flow reactor (EFR) at relatively high coal feed rates (0.5 g min{sup -1}). Seven coals ranging in rank from subbituminous to semianthracite, were tested and the evolved gases (O{sub 2}, CO, CO{sub 2}, NO) were measured continuously. The ignition temperature was evaluated from the gas evolution profiles, and it was found to be inversely correlated to the reactivity of the coal, as reflected by the increasing values of the ignition temperature in the sequence: subbituminous, high volatile bituminous, low volatile bituminous and semianthracite coals. The mechanism of ignition varied from a heterogeneous mechanism for subbituminous, low volatile bituminous and semianthracite coals, to a homogeneous mechanism for high volatile bituminous coals. A thermogravimetric analyser (TGA) was also used to evaluate coal ignition behaviour. Both methods, TGA and EFR, were in agreement as regards the mechanism of coal ignition. From the SEM micrographs of the coal particles retrieved from the cyclone, it was possible to observe the external appearance of the particles before, during and after ignition. The micrographs confirmed the mechanism deduced from the gas profiles. 23 refs., 5 figs., 1 tab.

  9. Development of balanced downflow type surface condensers, (2)

    International Nuclear Information System (INIS)

    Tomida, Akira; Oshima, Yoshikuni; Okochi, Isao; Izumi, Kenkichi.

    1976-01-01

    As the size of the condensers for power generation plants grew large, the new balanced downflow type condenser was developed and completed on the basis of the experiment on steam flow according to the two-dimensional flow model, the analysis of the performance in a tube nest with a computer, and the studies on the effect of outside liquid film and the reheating deaeration of condensate. When the balanced downflow type condensers were adopted for actual plants, the construction, strength and production method were examined, and the reliability of the new condenser was confirmed by the thermal characteristic experiment with the model similar to the actual machine. The condenser comprises a condenser body, supporting plates, cooling tubes, tube plates, water chambers, and reinforcements, and the cooling tubes are arranged so as to exchange heat effectively. The arrangement of tubes is divided into three regions, namely radiation portion, densely arranged portion, and air cooling portion. In the balanced downflow type condensers, the dilution by utilizing condensate is provided against ammonia attack. The apparatuses for the thermal characteristic experiment and the experimental results, and the results of the performance test on the actual balanced downflow type condenser are reported. (Kako, I.)

  10. Creepy landscapes : river sediment entrainment develops granular flow rheology on creeping bed.

    Science.gov (United States)

    Prancevic, J.; Chatanantavet, P.; Ortiz, C. P.; Houssais, M.; Durian, D. J.; Jerolmack, D. J.

    2015-12-01

    To predict rates of river sediment transport, one must first address the zeroth-order question: when does sediment move? The concept and determination of the critical fluid shear stress remains hazy, as observing particle motion and determining sediment flux becomes increasingly hard in its vicinity. To tackle this problem, we designed a novel annular flume experiment - reproducing an infinite river channel - where the refractive index of particles and the fluid are matched. The fluid is dyed with a fluorescent powder and a green laser sheet illuminates the fluid only, allowing us to observe particle displacements in a vertical plane. Experiments are designed to highlight the basic granular interactions of sediment transport while suppressing the complicating effects of turbulence; accordingly, particles are uniform spheres and Reynolds numbers are of order 1. We have performed sediment transport measurements close to the onset of particle motion, at steady state, and over long enough time to record averaged rheological behavior of particles. We find that particles entrained by a fluid exhibit successively from top to bottom: a suspension regime, a dense granular flow regime, and - instead of a static bed - a creeping regime. Data from experiments at a range of fluid stresses can be collapsed onto one universal rheologic curve that indicates the effective friction is a monotonic function of a dimensionless number called the viscous number. These data are in remarkable agreement with the local rheology model proposed by Boyer et al., which means that dense granular flows, suspensions and bed-load transport are unified under a common frictional flow law. Importantly, we observe slow creeping of the granular bed even in the absence of bed load, at fluid stresses that are below the apparent critical value. This last observation challenges the classical definition of the onset of sediment transport, and points to a continuous transition from quasi-static deformation to

  11. Maximizing biofuel production in a thermochemical biorefinery by adding electrolytic hydrogen and by integrating torrefaction with entrained flow gasification

    DEFF Research Database (Denmark)

    Clausen, Lasse Røngaard

    2015-01-01

    double the biofuel production per biomass input by converting almost all of the carbon in the biomass feed to carbon stored in the biofuel product. Water or steam electrolysis can supply the hydrogen to the biorefinery and also the oxygen for the gasifier. This paper presents the design and thermodynamic...... analysis of two biorefineries integrating water electrolysis for the production of methanol. In both plants, torrefied woody biomass is supplied to an entrained flow gasifier, but in one of the plants, the torrefaction process occurs on-site, as it is integrated with the entrained flow gasification process....... The analysis shows that the biorefinery with integrated torrefaction has a higher biomass to methanol energy ratio (136% vs. 101%) as well as higher total energy efficiency (62% vs. 56%). By comparing with two identical biorefineries without electrolysis, it is concluded that the biorefinery with integrated...

  12. Experimental and computational study and development of the bituminous coal entrained-flow air-blown gasifier for IGCC

    International Nuclear Information System (INIS)

    Abaimov, N A; Osipov, P V; Ryzhkov, A F

    2016-01-01

    In the paper the development of the advanced bituminous coal entrained-flow air- blown gasifier for the high power integrated gasification combined cycle is considered. The computational fluid dynamics technique is used as the basic development tool. The experiment on the pressurized entrained-flow gasifier was performed by “NPO CKTI” JSC for the thermochemical processes submodel verification. The kinetic constants for Kuznetsk bituminous coal (flame coal), obtained by thermal gravimetric analysis method, are used in the model. The calculation results obtained by the CFD model are in satisfactory agreements with experimental data. On the basis of the verified model the advanced gasifier structure was suggested which permits to increase the hydrogen content in the synthesis gas and consequently to improve the gas turbine efficiency. In order to meet the specified requirements vapor is added on the second stage of MHI type gasifier and heat necessary for air gasification is compensated by supplemental heating of the blasting air. (paper)

  13. Large eddy simulation study of the kinetic energy entrainment by energetic turbulent flow structures in large wind farms

    Science.gov (United States)

    VerHulst, Claire; Meneveau, Charles

    2014-02-01

    In this study, we address the question of how kinetic energy is entrained into large wind turbine arrays and, in particular, how large-scale flow structures contribute to such entrainment. Previous research has shown this entrainment to be an important limiting factor in the performance of very large arrays where the flow becomes fully developed and there is a balance between the forcing of the atmospheric boundary layer and the resistance of the wind turbines. Given the high Reynolds numbers and domain sizes on the order of kilometers, we rely on wall-modeled large eddy simulation (LES) to simulate turbulent flow within the wind farm. Three-dimensional proper orthogonal decomposition (POD) analysis is then used to identify the most energetic flow structures present in the LES data. We quantify the contribution of each POD mode to the kinetic energy entrainment and its dependence on the layout of the wind turbine array. The primary large-scale structures are found to be streamwise, counter-rotating vortices located above the height of the wind turbines. While the flow is periodic, the geometry is not invariant to all horizontal translations due to the presence of the wind turbines and thus POD modes need not be Fourier modes. Differences of the obtained modes with Fourier modes are documented. Some of the modes are responsible for a large fraction of the kinetic energy flux to the wind turbine region. Surprisingly, more flow structures (POD modes) are needed to capture at least 40% of the turbulent kinetic energy, for which the POD analysis is optimal, than are needed to capture at least 40% of the kinetic energy flux to the turbines. For comparison, we consider the cases of aligned and staggered wind turbine arrays in a neutral atmospheric boundary layer as well as a reference case without wind turbines. While the general characteristics of the flow structures are robust, the net kinetic energy entrainment to the turbines depends on the presence and relative

  14. Experiment study on NOx reduction through biomass reburning in an entrained flow reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lu, P.; Wang, Y.; Lu, F.; Liu, Y. [Nanjing Normal Univ. (China). School of Energy and Mechanical Engineering

    2013-07-01

    The reburning experiments with six kinds of biomass (including rice straw, wheat straw, maize stalk, cotton stalk, rice husk and bagasse,) and one biochar (wheat straw char) was carried out in an entrained flow reactor. The effects of biomass type, stoichiometric ratio in the reburning-zone (SR2), reaction temperature in the reburning-zone (t{sub 2}), particle sizes of biomass (d{sub p}), and reburning fuel fraction (R{sub ff}) on NO reduction efficiency analysed. The NO heterogeneous reduction contribute of biochar was also analyzed. The results indicate that NO reduction efficiency behaves a trend of first increase and then decrease with decreasing of SR2 or increasing of R{sub ff}. The higher NO reduction efficiency (more than 50%) can be achieved at the range of SR2 = 0.7-0.8 or R{sub ff} = 20-26% during reburning with six tested biomass. Cotton stalk with higher volatiles and the highest contents of K, Na alkali metals behaves the best performance of NO reduction. In the range of t{sub 2} = 900-1,100 C NO reduction efficiency increases with increasing of reburning-zone reaction temperature at the same SR2. NO reduction efficiency increases insignificantly with decreasing of particle size of biomass while d{sub p} < 425{mu}m. The contribution of NO heterogeneous reduction by wheat straw char to the total NO reduction is in the higher range of 59-68% while R{sub ff} = 10-26%.

  15. Parameterization of a numerical 2-D debris flow model with entrainment: a case study of the Faucon catchment, Southern French Alps

    Directory of Open Access Journals (Sweden)

    H. Y. Hussin

    2012-10-01

    Full Text Available The occurrence of debris flows has been recorded for more than a century in the European Alps, accounting for the risk to settlements and other human infrastructure that have led to death, building damage and traffic disruptions. One of the difficulties in the quantitative hazard assessment of debris flows is estimating the run-out behavior, which includes the run-out distance and the related hazard intensities like the height and velocity of a debris flow. In addition, as observed in the French Alps, the process of entrainment of material during the run-out can be 10–50 times in volume with respect to the initially mobilized mass triggered at the source area. The entrainment process is evidently an important factor that can further determine the magnitude and intensity of debris flows. Research on numerical modeling of debris flow entrainment is still ongoing and involves some difficulties. This is partly due to our lack of knowledge of the actual process of the uptake and incorporation of material and due the effect of entrainment on the final behavior of a debris flow. Therefore, it is important to model the effects of this key erosional process on the formation of run-outs and related intensities. In this study we analyzed a debris flow with high entrainment rates that occurred in 2003 at the Faucon catchment in the Barcelonnette Basin (Southern French Alps. The historic event was back-analyzed using the Voellmy rheology and an entrainment model imbedded in the RAMMS 2-D numerical modeling software. A sensitivity analysis of the rheological and entrainment parameters was carried out and the effects of modeling with entrainment on the debris flow run-out, height and velocity were assessed.

  16. A numerical model for chemical reaction on slag layer surface and slag layer behavior in entrained-flow gasifier

    Directory of Open Access Journals (Sweden)

    Liu Sheng

    2013-01-01

    Full Text Available The paper concerns with slag layer accumulation, chemical reaction on slag layer surface, and slag layer flow, heat and mass transfer on the wall of entrained-flow coal gasifier. A slag layer model is developed to simulate slag layer behaviors in the coal gasifier. This 3-D model can predict temperature, slag particle disposition rate, disposition particle composition, and syngas distribution in the gasifier hearth. The model is used to evaluate the effects of O2/coal ratio on slag layer behaviors.

  17. Behaviour of heavy metals during the thermal conversion of sawdust in an entrained flow reactor

    Energy Technology Data Exchange (ETDEWEB)

    Klensch, S.; Reimert, R. [Engler-Bunte-Inst., Bereich Gas, Erdoel und Kohle, Univ. Karlsruhe, Karlsruhe (Germany)

    1999-07-01

    Since its utilization is nearly CO{sub 2}-neutral, biomass represents a major alternative energy carrier in comparison with fossil fuels in CO{sub 2} reduction scenarios frequently discussed. Decentral generation of power and heat in medium sized plants could develop as a preferred application in future. During thermal conversion (gasification and combustion) of biomass the inorganic matter including the heavy metals will be found in the solid residues, i. e. slags and ashes, and in very low concentrations in the product gas (fuel or flue gas). The ashes should be returned to the forests and the agricultural areas respectively to avoid the use of industrial fertilizers. However, for this purpose the heavy metal concentrations of ashes may not exceed specific limit values, otherwise the returned ashes can lead to harmful effects on the ecological system. In awareness of this problem, in Austria some limit values for the concentrations of Cd, Cr, Cu, Ni, Pb and Zn in returned ashes are valid since 1997. No danger for the environment can be expected by slags containing heavy metals. The heavy metals are fixed environmentally neutral in the glass matrix as has been proven for coal and for residue gasification many times. Dividing the total of the residues into such two streams (returned ash and slag) avoids the disposal of the ashes. The heavy metal behaviour during the thermal conversion of sawdust was investigated in a bench scale plant. In essence, the plant consists of an entrained flow reactor (length of reaction zone: 2,500 mm; inner diameter: 70 mm) and a candle barrier filter with 6 rigid ceramic filter elements (DIA-Schumalith 10-20). The biomass flow rate is as high as 6 kg/h and the operating pressure is about 0.12 MPa. Experimental results show the influences of the conversion temperature (1100 - 1300 C), of the dedusting temperature (350 - 800 C), and of the gas atmosphere (reducing, oxidising) on the heavy metal concentrations of the slag and of the fly

  18. Analysis of transient flows in gasoline direct injection systems: effects on unsteady air entrainment by the spray; Analyse des ecoulements transitoires dans les systemes d'injection directe essence: effets sur l'entrainement d'air instationnaire du spray

    Energy Technology Data Exchange (ETDEWEB)

    Delay, G

    2005-03-15

    The aim of this study is to determine instantaneous liquid flow rate oscillations effect on non stationary air entrainment of an injector conical spray (Gasoline Direct Injection). The tools we use are either experimental or numerical ones. An instantaneous flow rate determination method is used. It is based on pulsated flows physics and only requires the velocity at the centerline of a pipe mounted just before the injector. So, it is possible to 'rebuild' the instantaneous velocity distributions and then to get the instantaneous liquid flow rate (Laser Doppler Anemometry measurements). A mechanical and hydraulics modeling software (AMESim) is necessary to get injector outlet flow rate. Simulations are validated by both 'rebuilding' method results and common rail pressure measurements. Fluorescent Particle Image Velocimetry (FPIV), suited to dense two -phase flows, is used to measure air flow around and inside the conical spray. Velocity measurements close to the spray frontier are used to compute instantaneous air entrainment. Considering droplets momentum exchange with air and thanks to droplets diameters and liquid velocities measurements at the nozzle exit, a transient air entrainment model is proposed according to FPIV measurements. (author)

  19. Effect of tides, river flow, and gate operations on entrainment of juvenile salmon into the interior Sacramento–San Joaquin River Delta

    Science.gov (United States)

    Perry, Russell W.; Brandes, Patricia L.; Burau, Jon R.; Sandstrom, Philip T.; Skalski, John R.

    2015-01-01

    Juvenile Chinook Salmon Oncorhynchus tshawytscha emigrating from natal tributaries of the Sacramento River, California, must negotiate the Sacramento-San Joaquin River Delta (hereafter, the Delta), a complex network of natural and man-made channels linking the Sacramento River with San Francisco Bay. Fish that enter the interior and southern Delta—the region to the south of the Sacramento River where water pumping stations are located—survive at a lower rate than fish that use alternative migration routes. Consequently, total survival decreases as the fraction of the population entering the interior Delta increases, thus spurring management actions to reduce the proportion of fish that are entrained into the interior Delta. To better inform management actions, we modeled entrainment probability as a function of hydrodynamic variables. We fitted alternative entrainment models to telemetry data that identified when tagged fish in the Sacramento River entered two river channels leading to the interior Delta (Georgiana Slough and the gated Delta Cross Channel). We found that the probability of entrainment into the interior Delta through both channels depended strongly on the river flow and tidal stage at the time of fish arrival at the river junction. Fish that arrived during ebb tides had a low entrainment probability, whereas fish that arrived during flood tides (i.e., when the river's flow was reversed) had a high probability of entering the interior Delta. We coupled our entrainment model with a flow simulation model to evaluate the effect of nighttime closures of the Delta Cross Channel gates on the daily probability of fish entrainment into the interior Delta. Relative to 24-h gate closures, nighttime closures increased daily entrainment probability by 3 percentage points on average if fish arrived at the river junction uniformly throughout the day and by only 1.3 percentage points if 85% of fish arrived at night. We illustrate how our model can be used to

  20. Phenomenological modelling of CHF in annular flow in annuli using new models of droplet deposition and entrainment

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haibin, E-mail: hb-zhang@xjtu.edu.cn [School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Department of Chemical Engineering, Imperial College, London SW7 2BY (United Kingdom); Hewitt, G.F., E-mail: g.hewitt@imperial.ac.uk [Department of Chemical Engineering, Imperial College, London SW7 2BY (United Kingdom)

    2016-08-15

    Highlights: • A phenomenological model to predict the CHF for flows in annuli is described. • New correlations of droplet entrainment and deposition are used. • The present model has good predictive capability in predicting CHF in annuli. - Abstract: In this paper, we present a phenomenological model to predict the CHF (critical heat flux) for upward annular flow in heated vertical annuli. In present model, a new set of correlations of droplet deposition and entrainment in annuli was used which were verified by comparison with the data of Moeck (1970) for developing liquid films in adiabatic annuli. In the results presented here, these new correlations have been used to predict 2249 independent data on critical heat flux (CHF) obtained both regarding internal heating of the rod as well as simultaneous heating of the rod and the outer tube in six heated vertical annuli under various mass flow rate, pressure and inlet quality and where the conditions were such that (as is most common) the CHF condition occurred in the annular flow regime. The comparisons between the calculated and measured CHFs showed that the present model has good predictive capability in predicting CHF.

  1. Study of parameters and entrainment of a jet in cross-flow arrangement with transition at two low Reynolds numbers

    Energy Technology Data Exchange (ETDEWEB)

    Cardenas, Camilo [Karlsruhe Institute of Technology, Institute for Chemical Technology and Polymer Chemistry, Karlsruhe (Germany); Convenio Andres Bello, Instituto Internacional de Investigaciones Educativas para la Integracion, La Paz (Bolivia); Denev, Jordan A.; Bockhorn, Henning [Karlsruhe Institute of Technology, Engler-Bunte-Institute, Combustion Division, Karlsruhe (Germany); Suntz, Rainer [Karlsruhe Institute of Technology, Institute for Chemical Technology and Polymer Chemistry, Karlsruhe (Germany)

    2012-10-15

    Investigation of the mixing process is one of the main issues in chemical engineering and combustion and the configuration of a jet into a cross-flow (JCF) is often employed for this purpose. Experimental data are gained for the symmetry plane in a JCF-arrangement of an air flow using a combination of particle image velocimetry (PIV) with laser-induced fluorescence (LIF). The experimental data with thoroughly measured boundary conditions are complemented with direct numerical simulations, which are based on idealized boundary conditions. Two similar cases are studied with a fixed jet-to-cross-flow velocity ratio of 3.5 and variable cross-flow Reynolds numbers equal to 4,120 and 8,240; in both cases the jet issues from the pipe at laminar conditions. This leads to a laminar-to-turbulent transition, which depends on the Reynolds number and occurs quicker for the case with higher Reynolds number in both experiments and simulations as well. It was found that the Reynolds number only slightly affects the jet trajectory, which in the case with the higher Reynolds number is slightly deeper. It is attributed to the changed boundary layer shape of the cross-flow. Leeward streamlines bend toward the jet and are responsible for the strong entrainment of cross-flow fluid into the jet. Velocity components are compared for the two Reynolds numbers at the leeward side at positions where strongest entrainment is present and a pressure minimum near the jet trajectory is found. The numerical simulations showed that entrainment is higher for the case with the higher Reynolds number. The latter is attributed to the earlier transition in this case. Fluid entrainment of the jet in cross-flow is more than twice stronger than for a similar flow of a jet issuing into a co-flowing stream. This comparison is made along the trajectory of the two jets at a distance of 5.5 jet diameters downstream and is based on the results from the direct numerical simulations and recently published

  2. Entrainment of bed material by Earth-surface mass flows: review and reformulation of depth-integrated theory

    Science.gov (United States)

    Iverson, Richard M.; Chaojun Ouyang,

    2015-01-01

    Earth-surface mass flows such as debris flows, rock avalanches, and dam-break floods can grow greatly in size and destructive potential by entraining bed material they encounter. Increasing use of depth-integrated mass- and momentum-conservation equations to model these erosive flows motivates a review of the underlying theory. Our review indicates that many existing models apply depth-integrated conservation principles incorrectly, leading to spurious inferences about the role of mass and momentum exchanges at flow-bed boundaries. Model discrepancies can be rectified by analyzing conservation of mass and momentum in a two-layer system consisting of a moving upper layer and static lower layer. Our analysis shows that erosion or deposition rates at the interface between layers must in general satisfy three jump conditions. These conditions impose constraints on valid erosion formulas, and they help determine the correct forms of depth-integrated conservation equations. Two of the three jump conditions are closely analogous to Rankine-Hugoniot conditions that describe the behavior of shocks in compressible gasses, and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries. Grain-fluid mixtures commonly behave as compressible materials as they undergo entrainment, because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow. If no bulk density change occurs, then only the shear-traction jump condition applies. Even for this special case, however, accurate formulation of depth-integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion.

  3. Measurement and modeling the coefficient of restitution of char particles under simulated entrained flow gasifier conditions

    Science.gov (United States)

    Gibson, LaTosha M.

    Inefficiencies in plant operations due to carbon loss in flyash, necessitate control of ash deposition and the handling of the slag disposal. Excessive char/ash deposition in convective coolers causes reduction in the heat transfer, both in the radiative (slagging) section and in the low-temperature convective (fouling) heating section. This can lead to unplanned shutdowns and result in an increased cost of electricity generation. CFD models for entrained flow gasification have used the average bulk coal composition to simulate slagging and ash deposition with a narrow particle size distribution (PSD). However, the variations in mineral (inorganic) and macerals (organic) components in coal have led to particles with a variation in their inorganic and organic composition after grinding as governed by their Particle Size Distribution (PSD) and mineral liberation kinetics. As a result, each particle in a PSD of coal exhibits differences in its conversion, particle trajectory within the gasifier, fragmentation, swelling, and slagging probability depending on the gasifier conditions (such as the temperature, coal to oxygen ratio, and swirling capacity of the coal injector). Given the heterogeneous behavior of char particles within a gasifier, the main objective of this work was to determine boundary conditions of char particle adhering and/or rebounding from the refractory wall or a layer of previously adhered particles. In the past, viscosity models based on the influence of ash composition have been used as the method to characterize sticking. It is well documented that carbon contributes to the non-wettability of particles. Therefore, it has been hypothesized that viscosity models would not be adequate to accurately predict the adhesion behavior of char. Certain particle wall impact models have incorporated surface tension which can account the contributions of the carbon content to the adhesive properties of a char particle. These particle wall impact models also

  4. Entrained-flow gasification at elevated pressure: Volume 1: Final technical report, March 1, 1985-April 30,1987

    Energy Technology Data Exchange (ETDEWEB)

    Hedman, P.O.; Smoot, L.D.; Smith, P.J.; Blackham, A.U.

    1987-10-15

    The general purpose of this research program was to develop a basic understanding of the physical and chemical processes in entrained coal gasification and to use the results to improve and evaluate an entrained gasification computer model. The first task included the collection and analysis of in-situ gasifier data at elevated pressures with three coal types (North Dakota lignite, Wyoming subbituminous and Illinois bituminous), the design, construction, and testing of new coal/oxygen/steam injectors with a fourth coal type (Utah bituminous), the collection of supporting turbulent fluid dynamic (LDV) data from cold-flow studies, and the investigation of the feasibility of using laser-based (CARS) daignostic instruments to make measurements in coal flames. The second task included improvements to the two-dimensional gasifier submodels, tabulation and evaluation of new coal devolatilization and char oxidation data for predictions, fundamental studies of turbulent particle dispersion, the development of improved numerical methods, and validation of the comprehensive model through comparison of predictions with experimental results. The third task was to transfer technical advances to industry and to METC through technical seminars, production of a detailed data book, code placement, and publication of results. Research results for these three tasks are summarized briefly here and presented in detail in the body of the report and in supporting references. 202 refs., 73 figs., 23 tabs.

  5. Effects of pressure on morphology and structure of bio-char from pressurized entrained-flow pyrolysis of microalgae

    Directory of Open Access Journals (Sweden)

    Kristina Maliutina

    2018-06-01

    Full Text Available The present dataset describes the entrained-flow pyrolysis of Microalgae Chlorella vulgaris and the results obtained during bio-char characterization. The dataset includes a brief explanation of the experimental procedure, experimental conditions and the influence of pyrolysis conditions on bio-chars morphology and carbon structure. The data show an increase in sphericity and surface smoothness of bio-chars at higher pressures and temperatures. Data confirmed that the swelling ratio of bio-chars increased with pressure up to 2.0 MPa. Consequently, changes in carbon structure of bio-chars were investigated using Raman spectroscopy. The data showed the increase in carbon order of chars at elevated pressures. Changes in the chemical structure of bio-char as a function of pyrolysis conditions were investigated using FTIR analysis. Keywords: Microalgae, Bio-char, Particle swelling, Pressurized pyrolysis

  6. Magnetic activity in the Galactic Centre region - fast downflows along rising magnetic loops

    Science.gov (United States)

    Kakiuchi, Kensuke; Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Enokiya, Rei; Machida, Mami; Matsumoto, Ryoji

    2018-06-01

    We studied roles of the magnetic field on the gas dynamics in the Galactic bulge by a three-dimensional global magnetohydrodynamical simulation data, particularly focusing on vertical flows that are ubiquitously excited by magnetic activity. In local regions where the magnetic field is stronger, it is frequently seen that fast downflows slide along inclined magnetic field lines that are associated with buoyantly rising magnetic loops. The vertical velocity of these downflows reaches ˜100 km s-1 near the footpoint of the loops by the gravitational acceleration towards the Galactic plane. The two footpoints of rising magnetic loops are generally located at different radial locations and the field lines are deformed by the differential rotation. The angular momentum is transported along the field lines, and the radial force balance breaks down. As a result, a fast downflow is often observed only at the one footpoint located at the inner radial position. The fast downflow compresses the gas to form a dense region near the footpoint, which will be important in star formation afterwards. Furthermore, the horizontal components of the velocity are also fast near the footpoint because the downflow is accelerated along the magnetic sliding slope. As a result, the high-velocity flow creates various characteristic features in a simulated position-velocity diagram, depending on the viewing angle.

  7. Compartment modeling of coal gasification in an entrained flow gasifier: A study on the influence of operating conditions

    International Nuclear Information System (INIS)

    Kong, Xiangdong; Zhong, Weimin; Du, Wenli; Qian, Feng

    2014-01-01

    Highlights: • Gasification of Shenfu coal in an industrial Texaco gasifier for syngas production. • An equivalent compartment model is developed using Aspen Plus. • Effects of operating parameters on gasification performance indices are studied. • Choosing a reasonable ROC to enhance the gasification efficiency can be flexible. - Abstract: Coal gasifiers are core components of coal-based polygeneration systems for power and chemical production. To study the effects of operational parameters on the performance of entrained flow coal gasifiers, this paper presents an equivalent compartment model (CM) using the Aspen Plus process simulator. The CM blocking is established based on gasifier flow field analysis, using a number of compartments. A simple configuration of these compartments involving material recirculation should be able to simulate the main flow and provide the temperature and gas component distributions. The model predictions exhibit good agreement with industrial data in the model validation. The influences of the oxygen-to-carbon ratio (ROC) and the coal slurry concentration on the gasification performance are discussed. Within the calculation range, the increase in the coal slurry concentration enhances the yield of the effective compositions in product gas. For a given slurry concentration of 62%, the efficient gas yield is a maximum for ROC of 1.43 kg/kg, whereas the oxygen consumption is a minimum for ROC of 1.37 kg/kg. According to the intended final use, however, choosing a reasonable ROC to obtain a higher efficient syngas yield and lower oxygen consumption can be flexible

  8. HELIOSEISMIC SIGNATURE OF CHROMOSPHERIC DOWNFLOWS IN ACOUSTIC TRAVEL-TIME MEASUREMENTS FROM HINODE

    International Nuclear Information System (INIS)

    Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.; Zhao Junwei; Tarbell, Theodore D.

    2009-01-01

    We report on a signature of chromospheric downflows in two emerging flux regions detected by time-distance helioseismology analysis. We use both chromospheric intensity oscillation data in the Ca II H line and photospheric Dopplergrams in the Fe I 557.6 nm line obtained by Hinode/SOT for our analyses. By cross-correlating the Ca II oscillation signals, we have detected a travel-time anomaly in the plage regions; outward travel times are shorter than inward travel times by 0.5-1 minute. However, such an anomaly is absent in the Fe I data. These results can be interpreted as evidence of downflows in the lower chromosphere. The downflow speed is estimated to be below 10 km s -1 . This result demonstrates a new possibility of studying chromospheric flows by time-distance analysis.

  9. Experimental investigation on an entrained flow type biomass gasification system using coconut coir dust as powdery biomass feedstock.

    Science.gov (United States)

    Senapati, P K; Behera, S

    2012-08-01

    Based on an entrained flow concept, a prototype atmospheric gasification system has been designed and developed in the laboratory for gasification of powdery biomass feedstock such as rice husks, coconut coir dust, saw dust etc. The reactor was developed by adopting L/D (height to diameter) ratio of 10, residence time of about 2s and a turn down ratio (TDR) of 1.5. The experimental investigation was carried out using coconut coir dust as biomass feedstock with a mean operating feed rate of 40 kg/h The effects of equivalence ratio in the range of 0.21-0.3, steam feed at a fixed flow rate of 12 kg/h, preheat on reactor temperature, product gas yield and tar content were investigated. The gasifier could able to attain high temperatures in the range of 976-1100 °C with gas lower heating value (LHV) and peak cold gas efficiency (CGE) of 7.86 MJ/Nm3 and 87.6% respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Development of a program BFQ/VER1 to simulate vapour pull through and liquid entrainment under stratified flow condition

    International Nuclear Information System (INIS)

    Majumdar, P.; Mukhopadyay, D.; Lele, H.G.; Gupta, S.K.

    2000-08-01

    Whether in process industries or nuclear industries, we come across lot of horizontal components, where two-phase or two-component fluids exist in normal or abnormal working conditions. Situations which lead to separation of the phases sees vapour pull through or liquid entrainment phenomena occurring when fluid discharges from horizontal components to the off - take branches. In order to capture the phenomena and applying it to the Indian PHWR during LOCA, a program 'BFQ' has been developed using various models for different fluids and conditions. These models have been validated with various experimental data available in the literature. Smoglie's model has been found to comply with most of the experiments even though it has been developed for air-water system. A modification of the model also been successfully used for feeders located at 45 deg. The result has been well validated with Hassan (1997) experiment for the same configuration. For a typical case of LOCA, RELAP4/MOD6, a widely used Homogenous model for simulating systems, is found to over predict the off-take flow quality from Header under stratified flow condition. (author)

  11. Effects of grid spacer with mixing vane on entrainments and depositions in two-phase annular flows

    Directory of Open Access Journals (Sweden)

    Akimaro Kawahara

    2015-06-01

    Full Text Available The effects of mixing vanes (MVs attached to a grid spacer on the characteristics of air–water annular flows were experimentally investigated. To know the effects, a grid spacer with or without MV was inserted in a vertical circular pipe of 16-mm internal diameter. For three cases (i.e., no spacer, spacer without MV, and spacer with MV, the liquid film thickness, liquid entrainment fraction, and deposition rate were measured by the constant current method, single liquid film extraction method, and double liquid film extraction method, respectively. The MVs significantly promote the re-deposition of liquid droplets in the gas core flow into the liquid film on the channel walls. The deposition mass transfer coefficient is three times higher for the spacer with MV than for the spacer without MV, even for cases 0.3-m downstream from the spacer. The liquid film thickness becomes thicker upstream and downstream for the spacer with MV, compared with the thickness for the spacer without MV and for the case with no spacer.

  12. Entrainment phenomenon in gas–liquid two-phase flow: A review

    Indian Academy of Sciences (India)

    into four categories: (a) mathematical description of the phenomenon using ... dome, (b) the central depressed portion rises up due to momentum of liquid, ... vapour velocity gets carried all the way in the vapour flow, which happens to be the minimum ..... included the droplet collection on the plate coated with carbon layer at ...

  13. Numerical fluid dynamics calculations of nonequilibrium steam-water flows with entrained droplets

    International Nuclear Information System (INIS)

    Williams, K.A.

    1984-01-01

    The present work has developed a computational fluid dynamics formulation that efficiently solves the conservation laws for a vapor field, a continuous liquid field, and two dispersed droplet fields. The thermal-hydraulic effects resulting from the exchange of mass, momentum and energy between the vapor and the dispersed droplet phases has been accurately modeled. This work is an advancement of the state-of-the-art for engineering analyses of nonequilibrium steam-water-droplet flows in heated channels. It is particularly applicable for boiling steam-water flows in which it is important to represent the effects of significant thermal nonequilibrium between the vapor and the liquid phases. This work was shown to be in good agreement with unique experimental measurements of significant thermal nonequilibrium between the vapor and dispersed droplets. The tests analyzed covered a range of mass fluxes and wall heating rates, and were all at low pressures where nonequilibrium effects are most pronounced

  14. Slagging Behavior of Straw and Corn Stover and the Fate of Potassium under Entrained-Flow Gasification Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Leiser, S.; Cieplik, M.K.; Smit, R. [Energy research Centre of the Netherlands ECN, Post Office Box 1, 1755 ZG Petten (Netherlands)

    2013-07-01

    The behavior of straw and corn stover (non-food agricultural residues potentially available for power generation) was studied in a lab-scale reactor under entrained-flow gasification conditions typical for existing integrated gasification combined cycle power systems. This experimental work was assisted by a range of ash-specific analyses and thermodynamic modeling to gain insights into both the physics and chemistry of ash formation and melting behavior. It was observed that, although the major part of the primarily siliceous native ash promptly forms a molten slag, much of the alkalis are evaporated into the syngas. These gas-borne alkalis can potentially cause aerosol formation in the gasifier, gas quench, syngas cooler, and quench systems, resulting in both operating problems (fouling) and emission issues. To minimize the alkali release from straw and corn stover, the addition of an additive (clay) has been proven to be a highly promising method without the negative effects for the melting behavior of the slag.

  15. Kinetics of devolatilization and oxidation of a pulverized biomass in an entrained flow reactor under realistic combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, Santiago [LITEC-CSIC (Spanish Council for Scientific Research), Maria de Luna 10, 50018 Zaragoza (Spain); Remacha, Pilar; Ballester, Javier [LITEC-CSIC (Spanish Council for Scientific Research), Maria de Luna 10, 50018 Zaragoza (Spain); Fluid Mechanics Group, University of Zaragoza, Maria de Luna 3, 50018 Zaragoza (Spain); Ballesteros, Juan C.; Gimenez, Antonio [ENDESA GENERACION, S.A., Ribera del Loira 60, 28042 Madrid (Spain)

    2008-03-15

    In this paper the results of a complete set of devolatilization and combustion experiments performed with pulverized ({proportional_to}500 {mu}m) biomass in an entrained flow reactor under realistic combustion conditions are presented. The data obtained are used to derive the kinetic parameters that best fit the observed behaviors, according to a simple model of particle combustion (one-step devolatilization, apparent oxidation kinetics, thermally thin particles). The model is found to adequately reproduce the experimental trends regarding both volatile release and char oxidation rates for the range of particle sizes and combustion conditions explored. The experimental and numerical procedures, similar to those recently proposed for the combustion of pulverized coal [J. Ballester, S. Jimenez, Combust. Flame 142 (2005) 210-222], have been designed to derive the parameters required for the analysis of biomass combustion in practical pulverized fuel configurations and allow a reliable characterization of any finely pulverized biomass. Additionally, the results of a limited study on the release rate of nitrogen from the biomass particle along combustion are shown. (author)

  16. Effect of oxy-fuel combustion with steam addition on coal ignition and burnout in an entrained flow reactor

    International Nuclear Information System (INIS)

    Riaza, J.; Alvarez, L.; Gil, M.V.; Pevida, C.; Pis, J.J.; Rubiera, F.

    2011-01-01

    The ignition temperature and burnout of a semi-anthracite and a high-volatile bituminous coal were studied under oxy-fuel combustion conditions in an entrained flow reactor (EFR). The results obtained under oxy-fuel atmospheres (21%O 2 -79%CO 2 , 30%O 2 -70% O 2 and 35%O 2 -65%CO 2 ) were compared with those attained in air. The replacement of CO 2 by 5, 10 and 20% of steam in the oxy-fuel combustion atmospheres was also evaluated in order to study the wet recirculation of flue gas. For the 21%O 2 -79%CO 2 atmosphere, the results indicated that the ignition temperature was higher and the coal burnout was lower than in air. However, when the O 2 concentration was increased to 30 and 35% in the oxy-fuel combustion atmosphere, the ignition temperature was lower and coal burnout was improved in comparison with air conditions. On the other hand, an increase in ignition temperature and a worsening of the coal burnout was observed when steam was added to the oxy-fuel combustion atmospheres though no relevant differences between the different steam concentrations were detected. -- Highlights: → The ignition temperature and the burnout of two thermal coals under oxy-fuel combustion conditions were determined. → The effect of the wet recirculation of flue gas on combustion behaviour was evaluated. → Addition of steam caused a worsening of the ignition temperature and coal burnout.

  17. Final Report: Pilot-scale Cross-flow Filtration Test - Envelope A + Entrained Solids

    Energy Technology Data Exchange (ETDEWEB)

    Duignan, M.R.

    2000-06-27

    This report discusses the results of the operation of a cross-flow filter in a pilot-scale experimental facility that was designed, built, and run by the Experimental Thermal Fluids Laboratory of the Savannah River Technology Center of the Westinghouse Savannah River Company.This filter technology was evaluated for its inclusion in the pretreatment section of the nuclear waste stabilization plant being designed by BNFL, Inc. This plant will be built at the U.S. Department of Energy's Hanford Site as part of the River Protection Project.

  18. Final Report: Pilot-scale Cross-flow Filtration Test - Envelope A + Entrained Solids

    International Nuclear Information System (INIS)

    Duignan, M.R.

    2000-01-01

    This report discusses the results of the operation of a cross-flow filter in a pilot-scale experimental facility that was designed, built, and run by the Experimental Thermal Fluids Laboratory of the Savannah River Technology Center of the Westinghouse Savannah River Company.This filter technology was evaluated for its inclusion in the pretreatment section of the nuclear waste stabilization plant being designed by BNFL, Inc. This plant will be built at the U.S. Department of Energy's Hanford Site as part of the River Protection Project

  19. Using Supra-Arcade Downflows as Probes of Particle Acceleration in Solar Flares

    Science.gov (United States)

    Savage, Sabrina

    2012-01-01

    Extracting information from coronal features above flares has become more reliable with the availability of increasingly higher spatial- and temporal-resolution data in recent decades. We are now able to sufficiently probe the region high above long-duration flaring active regions where reconnection is expected to be continually occurring. Flows in the supra-arcade region, first observed with Yohkoh/SXT, have been theorized to be associated with newly-reconnected outflowing loops. High resolution data appears to confirm these assertions. Assuming that these flows are indeed reconnection outflows, then the detection of those directed toward the solar surface (i.e. downflowing) should be associated with particle acceleration between the current sheet and the loop footpoints rooted in the chromosphere. RHESSI observations of highly energetic particles with respect to downflow detections could potentially constrain electron acceleration models. We provide measurements of these supra-arcade downflows (SADs) in relation to reconnection model parameters and present preliminary findings comparing the downflow timings with high-energy RHESSI lightcurves.

  20. Using Supra-Arcade Downflows as Probes of Electron Acceleration During Solar Flares

    Science.gov (United States)

    Savage, Sabrina L.

    2011-01-01

    Extracting information from coronal features above flares has become more reliable with the availability of increasingly higher spatial and temporal-resolution data in recent decades. We are now able to sufficiently probe the region high above long-duration flaring active regions where reconnection is expected to be continually occurring. Flows in the supra-arcade region, first observed with Yohkoh/SXT, have been theorized to be associated with newly-reconnected outflowing loops. High resolution data appears to confirm these assertions. Assuming that these flows are indeed reconnection outflows, then the detection of those directed toward the solar surface (i.e. downflowing) should be associated with particle acceleration between the current sheet and the loop footpoints rooted in the chromosphere. RHESSI observations of highly energetic particles with respect to downflow detections could potentially constrain electron acceleration models. I will discuss measurements of these supra-arcade downflows (SADs) in relation to reconnection model parameters and present preliminary findings comparing the downflow timings with high-energy RHESSI lightcurves.

  1. Entrainment by turbulent plumes

    Science.gov (United States)

    Parker, David; Burridge, Henry; Partridge, Jamie; Linden, Paul

    2017-11-01

    Plumes are of relevance to nature and real consequence to industry. While the Morton, Taylor & Turner (1956) plume model is able to estimate the mean physical flux parameters, the process of entrainment is only parametrised in a time-averaged sense and a deeper understanding is key to understanding how they evolve. Various flow configurations, resulting in different entrainment values, are considered; we perform simultaneous PIV and plume-edge detection on saline plumes in water resulting from a point source, a line source and a line source where a vertical wall is placed immediately adjacent. Of particular interest is the effect the large scale eddies, forming at the edge of the plume and engulfing ambient fluid, have on the entrainment process. By using velocity statistics in a coordinate system based on the instantaneous scalar edge of the plume the significance of this large scale engulfment is quantified. It is found that significant mass is transported outside the plumes, in particular in regions where large scale structures are absent creating regions of relatively high-momentum ambient fluid. This suggests that the large scale processes, whereby ambient fluid is engulfed into the plume, contribute significantly to the entrainment.

  2. Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795

    Science.gov (United States)

    Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Combes, F.; Edge, A. C.; Hogan, M. T.; McDonald, M.; Salomé, P.; Tremblay, G.; Vantyghem, A. N.

    2017-12-01

    We present new ALMA observations tracing the morphology and velocity structure of the molecular gas in the central galaxy of the cluster Abell 1795. The molecular gas lies in two filaments that extend 5-7 kpc to the N and S from the nucleus and project exclusively around the outer edges of two inner radio bubbles. Radio jets launched by the central active galactic nucleus have inflated bubbles filled with relativistic plasma into the hot atmosphere surrounding the central galaxy. The N filament has a smoothly increasing velocity gradient along its length from the central galaxy's systemic velocity at the nucleus to -370 km s^{-1}, the average velocity of the surrounding galaxies, at the furthest extent. The S filament has a similarly smooth but shallower velocity gradient and appears to have partially collapsed in a burst of star formation. The close spatial association with the radio lobes, together with the ordered velocity gradients and narrow velocity dispersions, shows that the molecular filaments are gas flows entrained by the expanding radio bubbles. Assuming a Galactic XCO factor, the total molecular gas mass is 3.2 ± 0.2 × 109 M⊙. More than half lies above the N radio bubble. Lifting the molecular clouds appears to require an infeasibly efficient coupling between the molecular gas and the radio bubble. The energy required also exceeds the mechanical power of the N radio bubble by a factor of 2. Stimulated feedback, where the radio bubbles lift low-entropy X-ray gas that becomes thermally unstable and rapidly cools in situ, provides a plausible model. Multiple generations of radio bubbles are required to lift this substantial gas mass. The close morphological association then indicates that the cold gas either moulds the newly expanding bubbles or is itself pushed aside and shaped as they inflate.

  3. A steady-state supersonic downflow in the transition region above a sunspot umbra

    Science.gov (United States)

    Straus, Thomas; Fleck, Bernhard; Andretta, Vincenzo

    2015-10-01

    We investigate a small-scale (~1.5 Mm along the slit), supersonic downflow of about 90 km s-1 in the transition region above the lightbridged sunspot umbra in AR 11836. The observations were obtained with the Interface Region Spectrograph (IRIS) on 2013 September 2 from 16:40 to 17:59 UT. The downflow shows up as redshifted "satellite" lines of the Si iv and O iv transition region lines and is remarkably steady over the observing period of nearly 80 min. The downflow is not visible in the chromospheric lines, which only show an intensity enhancement at the location of the downflow. The density inferred from the line ratio of the redshifted satellites of the O iv lines (Ne = 1010.6 ± 0.25 cm-3) is only a factor 2 smaller than the one inferred from the main components (Ne = 1010.95 ± 0.20 cm-3). Consequently, this implies a substantial mass flux (~5 × 10-7 g cm-2 s-1), which would evacuate the overlying corona on timescales close to 10 s. We interpret these findings as evidence of a stationary termination shock of a supersonic siphon flow in a cool loop that is rooted in the central umbra of the spot. The movie is available in electronic form at http://www.aanda.org

  4. An empirical correlation for the entrainment fraction at the onset of annular flow based on 2006 CHF look-up table

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Bo; Yang, Dongyu [Department of Mechanical Engineering, Rongcheng Campus, Harbin University of Science and Technology, Rongcheng 264300, Shandong (China); Gan, Zhihua, E-mail: gan_zhihua@zju.edu.cn [Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou (China); Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Hangzhou (China); National Quality Inspection Center of Refrigeration Equipment (Henan), Minquan (China)

    2017-06-15

    Highlights: • A parallel look-up table for the entrainment fraction at annular point was developed. • A correlation was given based on the selected database from 2006 CHF look-up table. • Its reliability on the other conditions in the look-up table was discussed. - Abstract: The critical heat flux (CHF) of gas-liquid flow plays an important role in the safety of industrial equipment. At present, the liquid film dryout model is widely used for predicting CHF in gas-liquid annular flow. Most parameters in this model can be determined by some empirical correlations which are valid under different conditions. However, up to now, the entrainment fraction at the onset of annular flow is always assumed due to the lack of relevant experimental data. In this paper, the normalized data of the 2006 CHF look-up table (LUT) which has been adopted widely, especially in the nuclear industry, were used. Firstly, the empirical correlations, provided for the onset of annular flow and the limiting quality, were employed. In the valid pressure and mass flux range of these correlations, the selected database from LUT was confirmed. Secondly, the liquid film model was built. The entrainment fraction at the onset of annular flow was obtained when the calculated CHF by the model agreed with the corresponding value in LUT. A parallel look-up table for it was developed. Its correlation including the Weber and the liquid Reynolds number at outlet was proposed. The errors are mostly within ±30%. Finally, its reliability on the other conditions in LUT, which are beyond the valid range of the empirical correlations used for determining the database, was discussed. All the conditions whose errors are outside ±30% of the predictions by the provided correlation were marked in the tables.

  5. Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers

    Science.gov (United States)

    Kaneko, Tetsuya Kenneth

    The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into porous ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 °C to 1600 °C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory material. Experimentation, characterization, and modeling show that gasifier slag infiltration into porous refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen

  6. Methanol production via pressurized entrained flow biomass gasification – Techno-economic comparison of integrated vs. stand-alone production

    International Nuclear Information System (INIS)

    Andersson, Jim; Lundgren, Joakim; Marklund, Magnus

    2014-01-01

    The main objective with this work was to investigate techno-economically the opportunity for integrated gasification-based biomass-to-methanol production in an existing chemical pulp and paper mill. Three different system configurations using the pressurized entrained flow biomass gasification (PEBG) technology were studied, one stand-alone plant, one where the bark boiler in the mill was replaced by a PEBG unit and one with a co-integration of a black liquor gasifier operated in parallel with a PEBG unit. The cases were analysed in terms of overall energy efficiency (calculated as electricity-equivalents) and process economics. The economics was assessed under the current as well as possible future energy market conditions. An economic policy support was found to be necessary to make the methanol production competitive under all market scenarios. In a future energy market, integrating a PEBG unit to replace the bark boiler was the most beneficial case from an economic point of view. In this case the methanol production cost was reduced in the range of 11–18 Euro per MWh compared to the stand-alone case. The overall plant efficiency increased approximately 7%-units compared to the original operation of the mill and the non-integrated stand-alone case. In the case with co-integration of the two parallel gasifiers, an equal increase of the system efficiency was achieved, but the economic benefit was not as apparent. Under similar conditions as the current market and when methanol was sold to replace fossil gasoline, co-integration of the two parallel gasifiers was the best alternative based on received IRR. - Highlights: • Techno-economic results regarding integration of methanol synthesis processes in a pulp and paper mill are presented. • The overall energy efficiency increases in integrated methanol production systems compared to stand-alone production units. • The economics of the integrated system improves compared to stand-alone alternatives. • Tax

  7. Method of producing gaseous products using a downflow reactor

    Science.gov (United States)

    Cortright, Randy D; Rozmiarek, Robert T; Hornemann, Charles C

    2014-09-16

    Reactor systems and methods are provided for the catalytic conversion of liquid feedstocks to synthesis gases and other noncondensable gaseous products. The reactor systems include a heat exchange reactor configured to allow the liquid feedstock and gas product to flow concurrently in a downflow direction. The reactor systems and methods are particularly useful for producing hydrogen and light hydrocarbons from biomass-derived oxygenated hydrocarbons using aqueous phase reforming. The generated gases may find used as a fuel source for energy generation via PEM fuel cells, solid-oxide fuel cells, internal combustion engines, or gas turbine gensets, or used in other chemical processes to produce additional products. The gaseous products may also be collected for later use or distribution.

  8. Entrainment and deposition studies in two-phase cross flow: comparison between air-water and steam-water in a square horizontal duct. Technical report (final)

    International Nuclear Information System (INIS)

    Berryman, R.J.; Ralph, J.C.; Wade, C.D.

    1981-03-01

    Air-water simulation studies of two phase steam water flow relevant to the upper plenum of a PWR during reflood situations have recently been undertaken at Harwell for the US Nuclear Regulatory Commission. In order to give confidence that the simulation fluids were capable of modelling the important features of the actual system, a relatively basic comparison experiment has been carried out. Water entrainment and deposition tests have been carried out on a pair of 2.5 cm diameter vertical rods mounted in a cross flow of steam or air in a 10.2 cm x 10.2 cm tunnel. The air and steam systems exhibited similar characteristics to one another. A 'critical' film flowrate was identified for the rods which, once reached, either by injection through the sinters or by entrainment from the main two phase stream, was not exceeded with further water addition. The 'critical' film flowrate decreased with increase of cross flow velocity and was lower for air than steam at the same velocity. The results from the air and steam tests were found to be reasonably well correlated on the basis of the cross flow momentum flux of the air or steam

  9. In-duct removal of mercury from coal-fired power plant flue gas by activated carbon: assessment of entrained flow versus wall surface contributions

    Energy Technology Data Exchange (ETDEWEB)

    Scala, F.; Chirone, R.; Lancia, A. [CNR, Naples (Italy). Institute for Research on Combustion

    2008-12-15

    In-duct mercury capture efficiency by activated carbon from coal-combustion flue gas was investigated. To this end, elemental mercury capture experiments were conducted at 100 C in a purposely designed 65-mm ID labscale pyrex apparatus operated as an entrained flow reactor. Gas residence times were varied between 0.7 and 2.0 s. Commercial-powdered activated carbon was continuously injected in the reactor and both mercury concentration and carbon elutriation rate were followed at the outlet. Transient mercury concentration profiles at the outlet showed that steady-state conditions were reached in a time interval of 15-20 min, much longer than the gas residence time in the reactor. Results indicate that the influence of the walls is non-negligible in determining the residence time of fine carbon particles in the adsorption zone, because of surface deposition and/or the establishment of a fluid-dynamic boundary layer near the walls. Total mercury capture efficiencies of 20-50% were obtained with carbon injection rates in the range 0.07-0.25 g/min. However, only a fraction of this capture was attributable to free-flowing carbon particles, a significant contribution coming from activated carbon staying near the reactor walls. Entrained bed experiments at lab-scale conditions are probably not properly representative of full-scale conditions, where the influence of wall interactions is lower. Moreover, previously reported entrained flow lab-scale mercury capture data should be reconsidered by taking into account the influence of particle-wall interactions.

  10. Mechanistic Model for Ash Deposit Formation in Biomass Suspension Firing. Part 1: Model Verification by Use of Entrained Flow Reactor Experiments

    DEFF Research Database (Denmark)

    Hansen, Stine Broholm; Jensen, Peter Arendt; Jappe Frandsen, Flemming

    2017-01-01

    used to describe the deposit formation rates and deposit chemistry observed in a series of entrained flow reactor (EFR) experiments using straw and wood as fuels. It was found that model #1 was not able to describe the observed influence of temperature on the deposit buildup rates, predicting a much...... differ in the description of the sticking probability of impacted particles: model #1 employs a reference viscosity in the description of the sticking probability, while model #2 combines impaction of viscoelastic particles on a solid surface with particle capture by a viscous surface. Both models were...

  11. Hydraulic Behavior in The Downflow Hanging Sponge Bioreactor

    Directory of Open Access Journals (Sweden)

    Izarul Machdar

    2016-12-01

    Full Text Available Performance efficiency in a Downflow Hanging Sponge (DHS bioreactor is associated with the amount of time that a wastewater remains in the bioreactor. The bioreactor is considered as a plug flow reactor and its hydraulic residence time (HRT depends on the void volume of packing material and the flow rate. In this study, hydraulic behavior of DHS bioreactor was investigated by using tracer method. Two types of sponge module covers, cylindrical plastic frame (module-1 and plastic hair roller (module-2, were investigated and compared. A concentrated NaCl solution used as an inert tracer and input as a pulse at the inlet of DHS bioreactor. Analysis of the residence time distribution (RTD curves provided interpretation of the index distribution or holdup water (active volume, the degree of short-circuiting, number of tanks in series (the plug flow characteristic, and the dispersion number. It was found that the actual HRT was primarily shorter than theoretical HRT of each test. Holdup water of the DHS bioreactor ranged from 60% to 97% and 36% to 60% of module-1 and module-2, respectively. Eventhough module-1 has higher effective volume than module-2, result showed that the dispersion numbers of the two modules were not significant difference. Furthermore, N-values were found larger at a higher flow rate. It was concluded that a DHS bioreactor design should incorporated a combination of water distributor system, higher loading rate at startup process to generate a hydraulic behavior closer to an ideal plug flow.ABSTRAKEfisiensi unjuk kerja bioreactor Downflow Hanging Sponge (DHS berkaitan dengan lamanya waktu tinggal limbah berada di dalam bioreaktor tersebut. Bioreaktor DHS dianggap sebagai seuatu reaktor aliran sumbat (plug flow dimana waktu tinggal hidraulik (HRT tergantung pada volume pori material isian dan laju alir. Dua jenis modul digunakan dalam penelitian ini, yang diberi nama dengan module-1 dan module-2 untuk melihat pengaruh jenis modul

  12. GCFR upflow/downflow study summary report

    International Nuclear Information System (INIS)

    Menzel, H.F.

    1979-08-01

    During the one-year study a conceptual upflow core plant design was developed and the downflow core plant reference design updated. A comparison was made between the two plant designs in critical areas of plant performance, safety, and licensing. The results of that comparison led to the recommendation to adopt an upflow core for the GCFR plant reference design. Although additional development and design efforts are required, the potential of residual heat removal by natural circulation alone offers a decisive safety and licensing advantage

  13. Quantitative Examination of a Large Sample of Supra-Arcade Downflows in Eruptive Solar Flares

    Science.gov (United States)

    Savage, Sabrina L.; McKenzie, David E.

    2011-01-01

    Sunward-flowing voids above post-coronal mass ejection flare arcades were first discovered using the soft X-ray telescope aboard Yohkoh and have since been observed with TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays). Supra-arcade downflow (SAD) observations suggest that they are the cross-sections of thin flux tubes retracting from a reconnection site high in the corona. Supra-arcade downflowing loops (SADLs) have also been observed under similar circumstances and are theorized to be SADs viewed from a perpendicular angle. Although previous studies have focused on dark flows because they are easier to detect and complementary spectral data analysis reveals their magnetic nature, the signal intensity of the flows actually ranges from dark to bright. This implies that newly reconnected coronal loops can contain a range of hot plasma density. Previous studies have presented detailed SAD observations for a small number of flares. In this paper, we present a substantial SADs and SADLs flare catalog. We have applied semiautomatic detection software to several of these events to detect and track individual downflows thereby providing statistically significant samples of parameters such as velocity, acceleration, area, magnetic flux, shrinkage energy, and reconnection rate. We discuss these measurements (particularly the unexpected result of the speeds being an order of magnitude slower than the assumed Alfven speed), how they were obtained, and potential impact on reconnection models.

  14. Dynamics and developing of natural circulation cooling from vertical upflow and downflow conditions

    International Nuclear Information System (INIS)

    Yang, B.W.; Ouyang, W.

    2004-01-01

    Several research programs have been conducted to evaluate the capability of natural circulation cooling of reactors following a loss of cooling accident. Both experimental and RELAP5 simulation results were obtained for these studies in a facility with vertical heated tube(s) and a unheated bypass channel. The analytical results showed that, under a certain power level, a natural circulation pattern can be developed from both initial upflow and downflow conditions, and maintained for a significant cooling period. This power level, for the discussion of this paper, is defined as the natural circulation cooling (NCC) power limit. Two import factors, namely the pump coastdown rate and the initial flow direction, are examined in this paper. In the benchmark case, as compared to the experimental results, the RELAP5 simulation program accurately predicted the transient phenomena from forced convection through flow reversal, then, into natural circulation cooling. Generally, the two-phase NCC power limit is higher and also more stable for the cases with initial upflow forced convection than for the cases with initial downflow. The transient phenomena (dynamics) of the natural circulation cooling was examined by varying the pump coast down rate in approaching the flow reversal natural circulation. A significant pump coastdown effect on the NCC power limit was observed for the analytical tests with initial downflow forced convection. For the tests with initial downflow condition, the higher the coastdown rate (or the shorter the coastdown period), the higher the NCC power limit. For the case with initial upflow forced convection, there may be an optimal coastdown rate for a given subcooled condition. However, for the subcooled condition used in this study, the effect of pump coast down rate is not as significant as in the downward forced convection. (author)

  15. On a criterion of incipient motion and entrainment into suspension of a particle from cuttings bed in shear flow of non-Newtonian fluid

    Science.gov (United States)

    Ignatenko, Yaroslav; Bocharov, Oleg; May, Roland

    2017-10-01

    Solids transport is a major issue in high angle wells. Bed-load forms by sediment while transport and accompanied by intermittent contact with stream-bed by rolling, sliding and bouncing. The study presents the results of a numerical simulation of a laminar steady-state flow around a particle at rest and in free motion in a shear flow of Herschel-Bulkley fluid. The simulation was performed using the OpenFOAM open-source CFD package. A criterion for particle incipient motion and entrainment into suspension from cuttings bed (Shields criteria) based on forces and torques balance is discussed. Deflection of the fluid parameters from the ones of Newtonian fluid leads to decreasing of the drag and lift forces and the hydrodynamic moment. Thus, the critical shear stress (Shields parameter) for the considered non-Newtonian fluid must be greater than the one for a Newtonian fluid.

  16. Analysis of transient flows in gasoline direct injection systems: effects on unsteady air entrainment by the spray; Analyse des ecoulements transitoires dans les systemes d'injection directe essence: effets sur l'entrainement d'air instationnaire du spray

    Energy Technology Data Exchange (ETDEWEB)

    Delay, G.

    2005-03-15

    The aim of this study is to determine instantaneous liquid flow rate oscillations effect on non stationary air entrainment of an injector conical spray (Gasoline Direct Injection). The tools we use are either experimental or numerical ones. An instantaneous flow rate determination method is used. It is based on pulsated flows physics and only requires the velocity at the centerline of a pipe mounted just before the injector. So, it is possible to 'rebuild' the instantaneous velocity distributions and then to get the instantaneous liquid flow rate (Laser Doppler Anemometry measurements). A mechanical and hydraulics modeling software (AMESim) is necessary to get injector outlet flow rate. Simulations are validated by both 'rebuilding' method results and common rail pressure measurements. Fluorescent Particle Image Velocimetry (FPIV), suited to dense two -phase flows, is used to measure air flow around and inside the conical spray. Velocity measurements close to the spray frontier are used to compute instantaneous air entrainment. Considering droplets momentum exchange with air and thanks to droplets diameters and liquid velocities measurements at the nozzle exit, a transient air entrainment model is proposed according to FPIV measurements. (author)

  17. Oxy-coal combustion in an entrained flow reactor: Application of specific char and volatile combustion and radiation models for oxy-firing conditions

    DEFF Research Database (Denmark)

    Álvarez, L.; Yin, Chungen; Riaza, J.

    2013-01-01

    The deployment of oxy-fuel combustion in utility boilers is one of the major options for CO2 capture. However, combustion under oxy-firing conditions differs from conventional air-firing combustion, e.g., in the aspect of radiative heat transfer, coal conversion and pollutants formation....... In this work, a numerical study on pulverised coal combustion was conducted to verify the applicability and accuracy of several sub-models refined for oxy-fuel conditions, e.g., gaseous radiative property model, gas-phase combustion mechanism and heterogeneous char reaction model. The sub-models were...... implemented in CFD (Computational Fluid Dynamics) simulations of combustion of three coals under air-firing and various oxy-firing (21-35% vol O2 in O2/CO2 mixture) conditions in an EFR (entrained flow reactor). The predicted coal burnouts and gaseous emissions were compared against experimental results...

  18. Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed and Entrained-Flow Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Buitrago, Paula A. [Univ. of Utah, Salt Lake City, UT (United States); Morrill, Mike [Univ. of Utah, Salt Lake City, UT (United States); Lighty, JoAnn S. [Univ. of Utah, Salt Lake City, UT (United States); Silcox, Geoffrey D. [Univ. of Utah, Salt Lake City, UT (United States)

    2009-06-01

    intraparticle diffusion. The Freundlich isotherm more accurately described in-flight mercury capture. Using these parameters, very little intraparticle diffusion was evident. Consistent with other data, smaller particles resulted in higher mercury uptake due to available surface area. Therefore, it is important to capture the particle size distribution in the model. At typical full-scale sorbent feed rates, the calculations underpredicted adsorption, suggesting that wall effects can account for as much as 50 percent of the removal, making it an important factor in entrained-mercury adsorption models.

  19. Low-altitude ion heating with downflowing and upflowing ions

    Science.gov (United States)

    Shen, Y.; Knudsen, D. J.; Burchill, J. K.; Howarth, A. D.; Yau, A. W.; James, G.; Miles, D.; Cogger, L. L.; Perry, G. W.

    2017-12-01

    Mechanisms that energize ions at the initial stage of ion upflow are still not well understood. We statistically investigate ionospheric ion energization and field-aligned motion at very low altitudes (330-730 km) using simultaneous plasma, magnetic field, wave electric field and optical data from the e-POP satellite. The high-time-resolution (10 ms) dataset enables us to study the micro-structures of ion heating and field-aligned ion motion. The ion temperature and field-aligned bulk flow velocity are derived from 2-D ion distribution functions measured by the SEI instrument. From March 2015 to March 2016, we've found 17 orbits (in total 24 ion heating periods) with clear ion heating signatures passing across the dayside cleft or the nightside auroral regions. Most of these events have consistent ion heating and flow velocity characteristics observed from both the SEI and IRM instruments. The perpendicular ion temperature goes up to 4.5 eV within a 2 km-wide region in some cases, in which the Radio Receiver Instrument (RRI) sees broadband extremely low frequency (BBELF) waves, demonstrating significant wave-ion heating down to as low as 350 km. The e-POP Fast Auroral Imager (FAI) and Magnetic Field (MGF) instruments show that many events are associated with active aurora and are within downward current regions. Contrary to what would be expected from mirror-force acceleration of heated ions, the majority of these heating events (17 out of 24) are associated with the core ion downflow rather than upflow. These statistical results provide us with new sights into ion heating and field-aligned flow processes at very low altitudes.

  20. Supra Arcade Downflows in the Earth's Magnetotail

    Science.gov (United States)

    Kobelski, A.; Savage, S. L.; Malaspina, D.

    2017-12-01

    Pinpointing the location of a single reconnection event in the corona is difficult due to observational constraints, although features directly resulting from this rapid reconfiguration of the field lines can be observed beyond the reconnection site. One set of such features are outflows in the form of post-reconnection loops, which have been linked to observations of supra-arcade downflows (SADs). SADs appear as sunward-traveling, density-depleted regions above flare arcades that develop during long duration eruptions. The limitations of remote sensing methods inherently results in ambiguities regarding the interpretation of SAD formation. Of particular interest is how these features are related to post-reconnection retracting magnetic field lines. In planetary magnetospheres, similar events to solar flares occur in the form of substorms, where reconnection in the anti-sunward tail of the magnetosphere causes field lines to retract toward the planet. Using data from the Time History of Events and Macroscopic Interactions during Substorms (THEMIS), we compare one particular aspect of substorms, dipolarization fronts, to SADs. Dipolarization fronts are observed as rapid but temporary changes in the magnetic field of the magnetotail plasma sheet into a more potential-like dipolar shape. These dipolarization fronts are believed to be retracting post-reconnection field lines. We combine data sets to show that the while the densities and magnetic fields involved vary greatly between the regimes, the plasma βs and Alfvén speeds are similar. These similarities allow direct comparison between the retracting field lines and their accompanying wakes of rarified plasma observed with THEMIS around the Earth to the observed morphological density depletions visible with XRT and AIA on the Sun. These results are an important source of feedback for models of coronal current sheets.

  1. Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

    Science.gov (United States)

    Tsvelodub, O. Yu; Bocharov, A. A.

    2017-09-01

    The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. The paper studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. The periodic and soliton steady-state traveling solutions of this equation have been numerically found. The analysis of branching of new families of steady-state traveling solutions has been performed. In particular, it is shown that this model equation has solutions in the form of solitons-humps.

  2. Techno-economic analysis of lignite fuelled IGCC with CO{sub 2} capture. Comparing fluidized bed and entrained flow gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Guangjian; Wu, Zhen; Zhang, Haiying [North China Electric Power Univ., Beijing (China). School of Energy and Power Engineering

    2013-07-01

    Integrated coal gasification combined cycle (IGCC) plants with pre-combustion capture of CO{sub 2} represent one of the most promising options for generating low-cost decarbonized power using bituminous coals. This work systematically quantify the effect of coal rank on the efficiency and economics of IGCC systems with CO2 capture and storage (CCS), with a special focus on comparison of systems using fluidized-bed gasifier (U-GAS) and entrained flow gasifier (Shell). It was found that the Shell IGCCs are little affect by low rank coal after pre-drying in terms of thermal efficiency and the levelized cost of electricity (LCOE) is only increase by 2-6% for lignite cases with and without CCS compared with bituminous coal cases. The specific CO{sub 2} emissions of U-GAS gasifier based lignite fuelled IGCC with CCS is 198 g/kWhe, almost two times of shell gasifier cases, mainly due to lower carbon conversion in the gasifier and the higher methane in the raw gas of gasifier. However, the total capital cost and COE of U-Gas IGCCs are 15-20% less than that of Shell IGCCs because of lower capital cost of gasifier, coal drying units and air separate units per kWe.

  3. Viscous entrainment on hairy surfaces

    Science.gov (United States)

    Nasto, Alice; Brun, P.-T.; Hosoi, A. E.

    2018-02-01

    Nectar-drinking bats and honeybees have tongues covered with hairlike structures, enhancing their ability to take up viscous nectar by dipping. Using a combination of model experiments and theory, we explore the physical mechanisms that govern viscous entrainment in a hairy texture. Hairy surfaces are fabricated using laser cut molds and casting samples with polydimethylsiloxane (PDMS) elastomer. We model the liquid trapped within the texture using a Darcy-Brinkmann-like approach and derive the drainage flow solution. The amount of fluid that is entrained is dependent on the viscosity of the fluid, the density of the hairs, and the withdrawal speed. Both experiments and theory reveal an optimal hair density to maximize fluid uptake.

  4. Final Report: Pilot-Scale X-Flow Filtration Test - Env C Plus Entrained Solids Plus Sr/TRU

    International Nuclear Information System (INIS)

    Duignan, M.R.

    2000-01-01

    This report discusses the results of the operation of a cross-flow filter in a pilot-scale experimental facility that was designed, built, and run by the Experimental Thermal Fluids Laboratory of the Savannah River Technology Center of the Westinghouse Savannah River Company. This filtration technology was evaluated for its inclusion in the pretreatment section of the nuclear waste stabilization plant being designed by BNFL, Inc. The plant will be built at the U.S. Department of Energy's Hanford Site as part of the River Protection Project

  5. Final Report: Pilot-Scale X-Flow Filtration Test - Env C Plus Entrained Solids Plus Sr/TRU

    Energy Technology Data Exchange (ETDEWEB)

    Duignan, M.R.

    2000-07-27

    This report discusses the results of the operation of a cross-flow filter in a pilot-scale experimental facility that was designed, built, and run by the Experimental Thermal Fluids Laboratory of the Savannah River Technology Center of the Westinghouse Savannah River Company. This filtration technology was evaluated for its inclusion in the pretreatment section of the nuclear waste stabilization plant being designed by BNFL, Inc. The plant will be built at the U.S. Department of Energy's Hanford Site as part of the River Protection Project.

  6. Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

    International Nuclear Information System (INIS)

    Yu Tsvelodub, O

    2016-01-01

    The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically. (paper)

  7. Thermodynamics of supra-arcade downflows in solar flares

    Science.gov (United States)

    Chen, Xin; Liu, Rui; Deng, Na; Wang, Haimin

    2017-10-01

    Context. Supra-arcade downflows (SADs) have been frequently observed during the gradual phase of solar flares near the limb. In coronal emission lines sensitive to flaring plasmas, they appear as tadpole-like dark voids against the diffuse fan-shaped "haze" above, flowing toward the well-defined flare arcade. Aims: We aim to investigate the evolution of SADs' thermal properties, and to shed light on the formation mechanism and physical processes of SADs. Methods: We carefully studied several selected SADs from two flare events and calculated their differential emission measures (DEMs) as well as DEM-weighted temperatures using data obtained by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory. Results: Our analysis shows that SADs are associated with a substantial decrease in DEM above 4 MK, which is 1-3 orders of magnitude smaller than the surrounding haze as well as the region before or after the passage of SADs, but comparable to the quiet corona. There is no evidence for the presence of the SAD-associated hot plasma (>20 MK) in the AIA data, and this decrease in DEM does not cause any significant change in the DEM distribution as well as the DEM-weighted temperature, which supports this idea that SADs are density depletion. This depression in DEM rapidly recovers in the wake of the SADs studied, generally within a few minutes, suggesting that they are discrete features. In addition, we found that SADs in one event are spatio-temporally associated with the successive formation of post-flare loops along the flare arcade. Movies associated to Figs. A.1 and A.2 are available at http://www.aanda.org

  8. Entrainment separator performance

    International Nuclear Information System (INIS)

    First, M.W.; Leith, D.

    1976-01-01

    Clean and dust-loaded ACS entrainment separators mounted upstream of HEPA filters were exposed to a combination of fine water mist and steam at about 70 0 C from one to four hours. In every trial, the ACS entrainment separator prevented measurable deterioration of performance in the following HEPA filter. Droplet size-efficiency evaluation of the ACS entrainment separators showed that, within the accuracy of the measurements, they meet all service requirements and are fully equal to the best separator units available for service on pressurized water reactors

  9. Novel intrinsic-based submodel for char particle gasification in entrained-flow gasifiers: Model development, validation and illustration

    International Nuclear Information System (INIS)

    Schulze, S.; Richter, A.; Vascellari, M.; Gupta, A.; Meyer, B.; Nikrityuk, P.A.

    2016-01-01

    Highlights: • Model resolving intra-particle species transport for char conversion was formulated. • TGA experiments of char particle conversion in gas flow were conducted. • The experimental results for char conversion validated the model. • CFD simulations of endothermic reactor with developed model were carried out. - Abstract: The final carbon conversion rate is of critical importance in the efficiency of gasifiers. Therefore, comprehensive modeling of char particle conversion is of primary interest for designing new gasifiers. This work presents a novel intrinsic-based submodel for the gasification of a char particle moving in a hot flue gas environment considering CO 2 and H 2 O as inlet species. The first part of the manuscript describes the model and its derivation. Validations against experiments carried out in this work for German lignite char are reported in the second part. The comparison between submodel predictions and experimental data shows good agreement. The importance of char porosity change during gasification is demonstrated. The third part presents the results of CFD simulations using the new submodel and a surface-based submodel for a generic endothermic gasifier. The focus of CFD simulations is to demonstrate the crucial role of intrinsic based heterogeneous reactions in the adequate prediction of carbon conversion rates.

  10. Green power production by co-gasification of biomass in coal-fired oxygen-blown entrained-flow based IGCC processes

    Energy Technology Data Exchange (ETDEWEB)

    Van Ree, R; Korbee, R; De Smidt, R P; Jansen, D [ECN Fuels Conversion and Environment, Petten (Netherlands); Baumann, H R; Ullrich, N [Krupp Uhde, Dortmund (Germany); Haupt, G; Zimmerman, [Siemens, Erlangen (Germany)

    1998-11-01

    The use of coal for large scale power production meets a growing environmental concern. In spite of the fact that clean coal conversion technologies integrated with high-efficiency power production facilities, such as IGCC, are developed, the aim for sustainable development strives for a power production system based on renewable energy sources. One of the most promising renewable energy sources that can be used in the Netherlands is biomass, i.e. organic waste materials and/or energy crops. To accelerate the introduction of this material, in a technical and economically acceptable way, co-gasification with fossil fuels, in particular coal, in large scale IGCC processes is considered. In this paper the technical feasibility, economic profitability, and environmental acceptability of co-gasification of biomass in coal-fired oxygen-blown entrained-flow based IGM is discussed. Both a base-case coal-fired oxygen-blown entrained-flow based IGCC process - showing strong resemblance to the Puertollano IGCC plant in Spain - and three co-gasification concepts, viz.: (1) a concept with separate dry coal and biomass feeding systems, (2) a concept with a combined dry coal/biomass-derived pyrolysis char feeding system, and (3) a concept with parallel biomass pre-treatment/gasification and combined fuel gas clean-up/power production, were defined for further consideration. The base-case system and the co-gasification concepts as well are modelled in the flowsheet simulation package ASPEN{sup +}. Steady-state integral system calculations resulted in an overall net electrical plant efficiency for the base-case system of 50. 1 %LHV (48.3 %HHV). Replacing about 10 % of the total thermal plant input (coal) by biomass (willow) resulted in a decrease of the overall net electrical plant efficiency of 1.4 to 2.1 %-points LHV, avoided specific CO2 emissions of 40-49 g/kWh{sub e}, and total avoided CO2 emissions of about 129 to 159 kt/a, all depending on the co-gasification concept

  11. Suspended sediment entrainment estimation in unsteady turbulent flows by means of a stochastic meted; Computo de la incorporacion de sedimento en suspension en flujos turbulentos no permanentes utilizando un enfoque estocastico

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Jose Fernando; Garcia, Marcelo Horacio [Universidad de Illinois (United States); Admiraal, David Mark [Universidad de Nebraska en Lincoln (United States)

    2001-06-01

    In order to compute the total amount and vertical distribution of suspended sediment, a reference concentration near the bed or entrainment function is needed, and considerable research effort has been dedicated to obtain such formulae. Several entrainment functions are available in the literature, but all of them have been developed for steady, uniform flow conditions. The ability of such relationships to predict entrainment rates in unsteady flows has not been demonstrated, nor has there been any attempt to develop a general formulation that work for both steady and unsteady flow conditions. The traditional approach relates the entrainment of sediment to the wall shear stress associated with skin friction in a deterministic way, providing only a relation between mean values. An alternative is to consider both the shear stress and the entrainment as stochastic turbulent quantities and to express them in terms of their probability density functions (PDFs). In this way, statistics of the entrainment can be obtained from measured shear stress PDFs, either in steady or unsteady situations, since the effect of unsteadiness is embedded in the PDF. This new methodology was used to estimate sediment entrainment produced by the passage of vessels in the Mississippi River and the Illinois River. Using a low order cumulant expansion to describe the PDF of the shear stress and a generalized version of Garcia and Parker's entrainment relationship, an expression for the average of the entrainment as a function of the average, variance, skewness of the shear stress distribution was obtained. Predictions compared favourably with values reported in the literature. [Spanish] Para calcular la cantidad total y distribucion vertical de sedimento en suspension es preciso conocer una concentracion de referencia cerca del lecho o funcion de incorporacion, para lo cual se ha hecho un considerable esfuerzo por obtener dichas formulas. Existen varias funciones de incorporacion en la

  12. Non-slag co-gasification of biomass and coal in entrained-bed furnace

    Science.gov (United States)

    Itaya, Yoshinori; Suami, Akira; Kobayashi, Nobusuke

    2018-02-01

    Gasification is a promising candidate of processes to upgrade biomass and to yield clean gaseous fuel for utilization of renewable energy resources. However, a sufficient amount of biomass is not always available to operate a large scale of the plant. Co-gasification of biomass with coal is proposed as a solution of the problem. Tar emission is another subject during operation in shaft or kiln type of gasifiers employed conventionally for biomass. The present authors proposed co-gasification of biomass and coal in entrained-bed furnace, which is a representative process without tar emission under high temperature, but operated so to collect dust as flyash without molten slag formation. This paper presents the works performed on co-gasification performance of biomass and pulverized coal to apply to entrained-bed type of furnaces. At first, co-gasification of woody powder and pulverized coal examined using the lab-scale test furnace of the down-flow entrained bed showed that the maximum temperatures in the furnace was over 1500 K and the carbon conversion to gas achieved at higher efficiency than 80-90 percent although the residence time in the furnace was as short as a few seconds. Non-slag co-gasification was carried out successfully without slag formation in the furnace if coal containing ash with high fusion temperature was employed. The trend suggesting the effect of reaction rate enhancement of co-gasification was also observed. Secondary, an innovative sewage sludge upgrading system consisting of self-energy recovery processes was proposed to yield bio-dried sludge and to sequentially produce char without adding auxiliary fuel. Carbonization behavior of bio-dried sludge was evaluated through pyrolysis examination in a lab-scale quartz tube reactor. The thermal treatment of pyrolysis of sludge contributed to decomposition and removal of contaminant components such as nitrogen and sulfur. The gasification kinetics of sludge and coal was also determined by a

  13. Detection of gas entrainment into liquid metals

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, T., E-mail: t.vogt@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Fluid Dynamics, 01328 Dresden (Germany); Boden, S. [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Fluid Dynamics, 01328 Dresden (Germany); Andruszkiewicz, A. [Faculty of Mechanical and Power Engineering, Wroclaw University of Technology (Poland); Eckert, K. [Technische Universität Dresden, Institute of Fluid Mechanics, 01062 Dresden (Germany); Eckert, S.; Gerbeth, G. [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Fluid Dynamics, 01328 Dresden (Germany)

    2015-12-01

    Highlights: • We present liquid metal experiments dedicated to gas entrainment on the free surface. • Ultrasonic and X-ray attenuation techniques have been used to study the mechanisms of gas entrainment. • A comparison between bubbly flow in water and GaInSn showed substantial differences. • Our results emphasize the importance of liquid metal experiments which are able to provide a suitable data base for numerical code validation. - Abstract: Entrainment of cover gas into the liquid metal coolant is one of the principal safety issues in the design of innovative liquid metal-cooled fast reactors. We present generic experimental studies of this phenomenon in low-melting metals. Ultrasonic and X-ray diagnostic tools were considered for a visualization of gas entrainment at the free surface of the melt. Laboratory experiments were conducted using the eutectic alloy GaInSn, which is liquid at room temperature. Vortex-activated entrainment of air at the free surface of a rotating flow was revealed by ultrasonic techniques. X-ray radioscopy was used to visualize the behavior of argon bubbles inside a slit geometry. The measurements reveal distinct differences between water and GaInSn, especially with respect to the process of bubble formation and the coalescence and breakup of bubbles. Our results emphasize the importance of liquid metal experiments which are able to provide a suitable data base for numerical code validation.

  14. Experimental study of gas entrainment from surface swirl

    Energy Technology Data Exchange (ETDEWEB)

    Moudjed, B., E-mail: brahim.moudjed@cea.fr; Excoffon, J.; Riva, R.; Rossi, L., E-mail: lionel.rossi@cea.fr

    2016-12-15

    Gas entrainment from surface swirls is characterized using water experiments. A free surface shear flow is generated in an open channel flow. A suction nozzle is set at the bottom of the test section to induce a downward flow and provoke gas entrainment. An important originality of these experiments is the possibility to change the inlet condition so as to generate different turbulent shear flows. This is done by adding obstacles of different sizes and shapes at the end of a flat plate separating the inlet flow from a “stagnant” water area. Velocity fields and profiles, measured with the PIV technique, are provided both to describe the inlet conditions corresponding to various geometries and flow rates, and to characterize the temporal average shear flow generated within the centre part of the channel. Gas entrainment mappings are established from direct observations of the different flow configurations. These new results show that the threshold for the suction velocities required to entrain gas are similar for the configurations with small obstacles and the flat plate configuration triggering a standard shear flow. Increasing the size of the obstacles promotes gas entrainment and reduces the threshold values of the suction velocity to trigger gas entrainment. Shadowgraphy with image processing is used to present new results characterizing the geometrical properties of surface swirls and the quantity of gas entrained. Inlet configurations with obstacles generate larger surface swirls which move upstream from the suction nozzle centre whereas they are situated downstream with the flat plate configuration. Moreover, dimensionless power laws are found to be good approximations for the surface swirl width and the quantity of gas entrained. In addition to provide new insights about gas entrainment in analytical configurations relevant to Sodium cooled fast nuclear reactor, these results should provide different test cases for the validation of MCFD codes.

  15. Epitaxial growth of GaN by radical-enhanced metalorganic chemical vapor deposition (REMOCVD) in the downflow of a very high frequency (VHF) N2/H2 excited plasma - effect of TMG flow rate and VHF power

    Science.gov (United States)

    Lu, Yi; Kondo, Hiroki; Ishikawa, Kenji; Oda, Osamu; Takeda, Keigo; Sekine, Makoto; Amano, Hiroshi; Hori, Masaru

    2014-04-01

    Gallium nitride (GaN) films have been grown by using our newly developed Radical-Enhanced Metalorganic Chemical Vapor Deposition (REMOCVD) system. This system has three features: (1) application of very high frequency (60 MHz) power in order to increase the plasma density, (2) introduction of H2 gas together with N2 gas in the plasma discharge region to generate not only nitrogen radicals but also active NHx molecules, and (3) radical supply under remote plasma arrangement with suppression of charged ions and photons by employing a Faraday cage. Using this new system, we have studied the effect of the trimethylgallium (TMG) source flow rate and of the plasma generation power on the GaN crystal quality by using scanning electron microscopy (SEM) and double crystal X-ray diffraction (XRD). We found that this REMOCVD allowed the growth of epitaxial GaN films of the wurtzite structure of (0001) orientation on sapphire substrates with a high growth rate of 0.42 μm/h at a low temperature of 800 °C. The present REMOCVD is a promising method for GaN growth at relatively low temperature and without using costly ammonia gas.

  16. Characteristics of Air Entrainment in Hydraulic Jump

    Science.gov (United States)

    Albarkani, M. S. S.; Tan, L. W.; Al-Gheethi, A.

    2018-04-01

    The characteristics of hydraulic jump, especially the air entrainment within jump is still not properly understood. Therefore, the current work aimed to determine the size and number of air entrainment formed in hydraulic jump at three different Froude numbers and to obtain the relationship between Froude number with the size and number of air entrainment in hydraulic jump. Experiments of hydraulic jump were conducted in a 10 m long and 0.3 m wide Armfield S6MKII glass-sided tilting flume. Hydraulic jumps were produced by flow under sluice gate with varying Froude number. The air entrainment of the hydraulic jump was captured with a Canon Power Shot SX40 HS digital camera in video format at 24 frames per second. Three discharges have been considered, i.e. 0.010 m3/s, 0.011 m3/s, and 0.013 m3/s. For hydraulic jump formed in each discharge, 32 frames were selected for the purpose of analysing the size and number of air entrainment in hydraulic jump. The results revealed that that there is a tendency to have greater range in sizes of air bubbles as Fr1 increases. Experiments with Fr1 = 7.547. 7.707, and 7.924 shown that the number of air bubbles increases exponentially with Fr1 at a relationship of N = 1.3814 e 0.9795Fr1.

  17. Water Entrainment in Concrete

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben

    This report gives a survey of different techniques for incorporation of designed, water-filled cavities in concrete: Water entrainment. Also an estimate of the optimum size of the water inclusions is given. Water entrainment can be used to avoid self-desiccation and self-desiccation shrinkage...... during hydration [1,26]. What is needed is some sort of container which retains the shape of the water when mixed into the concrete. The container may function based on several different physical or chemical principles. Cells and gels are examples of containers found in nature. A cell membrane provides...... a boundary to water, whereas a polymer network incorporates water in its intersticious space with its affinity due to interaction energy and polymer entropy. Such containers allow water to be stored as an entity. In relation to concrete the water encapsulation may be accomplished either before or after start...

  18. Measurement of air entrainment in plasma jets

    International Nuclear Information System (INIS)

    Fincke, J.R.; Rodriquez, R.; Pentecost, C.G.

    1990-01-01

    The concentration and temperature of air entrained into argon and helium plasma jets has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The argon plasma flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition of turbulence occurs, air is rapidly mixed into the jet core. The location of the transition region is determined by the rapid cooling of the jet and the resulting increase in Reynolds number. In contrast, the helium plasma flow field never exceeds a Reynolds number of 200 and remains laminar. The entrainment process in this case is controlled by molecular diffusion rather than turbulent mixing. 9 refs., 5 figs., 1 tab

  19. The effect of acceleration on turbulent entrainment

    International Nuclear Information System (INIS)

    Breidenthal, Robert E

    2008-01-01

    A new class of self-similar turbulent flows is proposed, which exhibits dramatically reduced entrainment rates. Under strong acceleration, the rotation period of the large-scale vortices is forced to decrease linearly in time. In ordinary unforced turbulence, the rotation period always increases linearly with time, at least in the mean. However, by imposing an exponential acceleration on the flow, the vortex rotation period is forced to become the e-folding timescale of the acceleration. If the e-folding timescale itself decreases linearly in time, the forcing is 'super-exponential', characterized by an acceleration parameter α. Based on dimensional and heuristic arguments, a model suggests that the dissipation rate is an exponential function of α and the dimensions of the conserved quantity of the flow. Acceleration decreases the dissipation and entrainment rates in all canonical laboratory flows except for Rayleigh-Taylor. Experiments of exponential jets and super-exponential transverse jets are in accord with the model. As noted by Johari, acceleration is the only known means of affecting the entrainment rate of the far-field jet. Numerical simulations of Rayleigh-Taylor flow by Cook and Greenough are also consistent. In the limit of large acceleration, vortices do not move far before their rotation period changes substantially. In this sense, extreme acceleration corresponds to stationary vortices.

  20. Effects of the proposed California WaterFix North Delta Diversion on flow reversals and entrainment of juvenile Chinook salmon (Oncorhynchus tshawytscha) into Georgiana Slough and the Delta Cross Channel, northern California

    Science.gov (United States)

    Perry, Russell W.; Romine, Jason G.; Pope, Adam C.; Evans, Scott D.

    2018-02-27

    The California Department of Water Resources and Bureau of Reclamation propose new water intake facilities on the Sacramento River in northern California that would convey some of the water for export to areas south of the Sacramento-San Joaquin River Delta (hereinafter referred to as the Delta) through tunnels rather than through the Delta. The collection of water intakes, tunnels, pumping facilities, associated structures, and proposed operations are collectively referred to as California WaterFix. The water intake facilities, hereinafter referred to as the North Delta Diversion (NDD), are proposed to be located on the Sacramento River downstream of the city of Sacramento and upstream of the first major river junction where Sutter Slough branches from the Sacramento River. The NDD can divert a maximum discharge of 9,000 cubic feet per second (ft3/s) from the Sacramento River, which reduces the amount of Sacramento River inflow into the Delta.In this report, we conducted three analyses to investigate the effect of the NDD and its proposed operation on entrainment of juvenile Chinook salmon (Oncorhynchus tshawytscha) into Georgiana Slough and the Delta Cross Channel (DCC). Fish that enter the interior Delta (the network of channels to the south of the Sacramento River) through Georgiana Slough and the DCC survive at lower rates than fish that use other migration routes (Sacramento River, Sutter Slough, and Steamboat Slough). Therefore, fisheries managers were concerned about the extent to which operation of the NDD would increase the proportion of the population entering the interior Delta, which, all else being equal, would lower overall survival through the Delta by increasing the fraction of the population subject to lower survival rates. Operation of the NDD would reduce flow in the Sacramento River, which has the potential to increase the magnitude and duration of reverse flows of the Sacramento River downstream of Georgiana Slough.In the first analysis, we

  1. Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

    Directory of Open Access Journals (Sweden)

    M. Endo

    2000-02-01

    Full Text Available We have determined the MLT distribution and KP dependence of the ion upflow and downflow of the thermal bulk oxygen ion population based on a data analysis using the EISCAT VHF radar CP-7 data obtained at Tromsø during the period between 1990 and 1996: (1 both ion upflow and downflow events can be observed at any local time (MLT, irrespective of dayside and nightside, and under any magnetic disturbance level, irrespective of quiet and disturbed levels; (2 these upflow and downflow events are more frequently observed in the nightside than in the dayside; (3 the upflow events are more frequently observed than the downflow events at any local time except midnight and at any KP level and the difference of the occurrence frequencies between the upflow and downflow events is smaller around midnight; and (4 the occurrence frequencies of both the ion upflow and downflow events appear to increase with increasing KP level, while the occurrence frequency of the downflow appears to stop increasing at some KP level.Key words: Ionosphere (particle acceleration; plasma waves and instabilities - Space plasma physics (transport processes

  2. Experimental research of liquid entrainment through ADS-4 in AP1000

    International Nuclear Information System (INIS)

    Meng, Zhaoming; Dong, Bo; Wang, Laishun; Fu, Xiaoliang; Tian, Wenxi; Yang, Yanhua; Su, Guanghui

    2014-01-01

    Highlights: • We performed experimental research of liquid entrainment through ADS-4 in AP1000. • Effect of various factors on entrainment at T-junction was conducted. • Visualization research was conducted to make entrainment mechanism clear. - Abstract: In this study, based on a T-junction that consists of Automatic Depressurization System Stage Four (ADS-4) and hot leg in an AP1000 plant, a small-scale experimental research on entrainment at a T-junction was performed. This study mainly focused on the effect of various factors on entrainment, such as the effect of branch size, branch shape and liquid crossflow. The flow pattern map was plotted from the experimental data, and the visualization research indicated that the entrainment phenomena through a large size branch were apparently different from that through a small branch. Three entrainment phenomena were observed in the studies, two entrainment mechanisms could be found in the stratified flow regime entrainment area, the existence of branch contributed to generating intermittent flow in the horizontal main pipe, and the backflow region was observable in the vicinity of a large size branch inlet. Also, experimental research showed that downstream of the branch of T-junction had an important effect on the onset entrainment, and liquid crossflow did not seem to affect the onset entrainment

  3. Sediment particle entrainment in an obstructed annular

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, Bruno Venturini; Siqueira, Renato do Nascimento [Faculdade do Centro Leste (UCL), Serra, ES (Brazil). Lab. de Fenomenos de Transporte], e-mail: brunovl@ucl.br, e-mail: renatons@ucl.br

    2006-07-01

    Flow in an annular region with internal cylinder rotation is a classic problem in fluid mechanics and has been widely studied. Besides its importance as a fundamental problem, flow in annular regions has several practical applications. This project was motivated by an application of this kind of flow to the drilling of oil and gas wells. In this work, an erosion apparatus was constructed in order to study the effect of the internal cylinder rotation on particle entrainment in an obstructed annular space and bed package as well. The study also analyzed the influence of height of the particles bed on the process performance. The experiment was designed so that the internal cylinder rotation could be measured by an encoder. The fluid temperature was measured by a thermocouple and the experiments were carried out at the temperature of 25 deg C. The study revealed that the particle entrainment for the height of the bed that is close to the center of the cylinders is negligible and the internal cylinder rotation provokes the movement and packing of the bed. For lower height of the bed, with same dimension of the annular gap, the particle entrainment process was satisfactory and the bed compaction was smaller than in the previous case, leading to a more efficient cleaning process in the annular space. (author)

  4. MHD simulations of coronal dark downflows considering thermal conduction

    Science.gov (United States)

    Zurbriggen, E.; Costa, A.; Esquivel, A.; Schneiter, M.; Cécere, M.

    2017-10-01

    While several scenarios have been proposed to explain supra-arcade downflows (SADs) observed descending through turbulent hot regions, none of them have systematically addressed the consideration of thermal conduction. The SADs are known to be voided cavities. Our model assumes that SADs are triggered by bursty localized reconnection events that produce non-linear waves generating the voided cavity. These subdense cavities are sustained in time because they are hotter than their surrounding medium. Due to the low density and large temperature values of the plasma we expect the thermal conduction to be an important process. Our main aim here is to study if it is possible to generate SADs in the framework of our model considering thermal conduction. We carry on 2D MHD simulations including anisotropic thermal conduction, and find that if the magnetic lines envelope the cavities, they can be isolated from the hot environment and be identified as SADs.

  5. Spicular downflows in late-type giant coronae

    International Nuclear Information System (INIS)

    Wallenhorst, S.G.

    1980-01-01

    Models of the coronae of late-type stars are considered, under the assumption that the dominant coronal energy loss is not conduction, as is usually assumed, but rather the losses due to hot spicular material falling back onto the chromosphere. This assumption is used to estimated the increase in stellar mass-loss rate which should occur when stars evolve across the so-called Supersonic Transition Locus (STL). For a constant downward number flux, this increase is estimate to be about one order of magnitude. Energy-balance models are then considered for spicule-dominated coronae, under the additional assumption that the energy input flux to the corona is constant over a star's post-main sequence evolution; this assumption is found to be consistent with observed red giant mass-loss rates. A sequence of models is constructed which enables the various coronal parameters to be estimated for different masses and radii. The models yield results similar to those of the minimum flux coronal theory of A.G. Hearn; these similarities, along with the validity of the minimum flux technique, are discussed. It is shown that several criticisms of the minimum flux method, due to Antiochos and Underwood (1978) and Van Tend (1979), are valid for minimum flux models in which spicular downflow is neglected, but are satisfied by the models considered below. Solutions which precisely satisfy the constant-flux assumption are not found to exist for solar mass stars. Under the assumption that the minimum flux theory is correct, and using a downflow number flux derived from the energy-balance model, the jump in mass-loss rate at the STL is reevaluated. In this more rigorous case, the jump is found to be only about a factor of three. It is concluded that large increases in mass-loss rate are not to be expected as stars evolve across this transition locus

  6. Fluid Dynamics of Pressurized, Entrained Coal Gasifiers

    International Nuclear Information System (INIS)

    1997-01-01

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle--rather than discard--gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-upon the fluid dynamics of PECGs. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements

  7. OBSERVATION AND ANALYSIS OF BALLISTIC DOWNFLOWS IN AN M-CLASS FLARE WITH THE INTERFACE REGION IMAGING SPECTROGRAPH

    Energy Technology Data Exchange (ETDEWEB)

    Brannon, Sean R. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2016-12-10

    Despite significant advances in instrumentation, there remain no studies that analyze observations of on-disk flare loop plasma flows covering the entire evolution from chromospheric evaporation, through plasma cooling, to draining downflows. We present results from an imaging and spectroscopic observation from the Interface Region Imaging Spectrograph ( IRIS ) of the SOL2015–03–12T11:50:00 M-class flare, at high spatial resolution and time cadence. Our analysis of this event reveals initial plasma evaporation at flare temperatures indicated by 100–200 km s{sup −1} blueshifts in the Fe xxi line. We subsequently observe plasma cooling into chromospheric lines (Si iv and O iv) with ∼11 minute delay, followed by loop draining at ∼40 km s{sup −1} as indicated by a “C”-shaped redshift structure and significant (∼60 km s{sup −1}) non-thermal broadening. We use density-sensitive lines to calculate a plasma density for the flare loops, and estimate a theoretical cooling time approximately equal to the observed delay. Finally, we use a simple elliptical free-fall draining model to construct synthetic spectra, and perform what we believe to be the first direct comparison of such synthetic spectra to observations of draining downflows in flare loops.

  8. Experimental study of near-field entrainment of moderately overpressured jets

    Science.gov (United States)

    Solovitz, S.A.; Mastin, L.G.; Saffaraval, F.

    2011-01-01

    Particle image velocimetry (PIV) experiments have been conducted to study the velocity flow fields in the developing flow region of high-speed jets. These velocity distributions were examined to determine the entrained mass flow over a range of geometric and flow conditions, including overpressured cases up to an overpressure ratio of 2.83. In the region near the jet exit, all measured flows exhibited the same entrainment up until the location of the first shock when overpressured. Beyond this location, the entrainment was reduced with increasing overpressure ratio, falling to approximately 60 of the magnitudes seen when subsonic. Since entrainment ratios based on lower speed, subsonic results are typically used in one-dimensional volcanological models of plume development, the current analytical methods will underestimate the likelihood of column collapse. In addition, the concept of the entrainment ratio normalization is examined in detail, as several key assumptions in this methodology do not apply when overpressured.

  9. Numerical study on modeling of liquid film flow under countercurrent flow limitation in volume of fluid method

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Taro, E-mail: watanabe_t@qe.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita-shi, Osaka 565-7895 (Japan); Takata, Takashi, E-mail: takata.takashi@jaea.go.jp [Japan Atomic Energy Agency, 4002 Narita-chou, Oarai-machi, Higashi-Ibaraki-gun, Ibaraki 331-1393 (Japan); Yamaguchi, Akira, E-mail: yamaguchi@n.t.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki 319-1188 (Japan)

    2017-03-15

    Highlights: • Thin liquid film flow under CCFL was modeled and coupled with the VOF method. • The difference of the liquid flow rate in experiments of CCFL was evaluated. • The proposed VOF method can quantitatively predict CCFL with low computational cost. - Abstract: Countercurrent flow limitation (CCFL) in a heat transfer tube at a steam generator (SG) of pressurized water reactor (PWR) is one of the important issues on the core cooling under a loss of coolant accident (LOCA). In order to improve the prediction accuracy of the CCFL characteristics in numerical simulations using the volume of fluid (VOF) method with less computational cost, a thin liquid film flow in a countercurrent flow is modeled independently and is coupled with the VOF method. The CCFL characteristics is evaluated analytically in condition of a maximizing down-flow rate as a function of a void fraction or a liquid film thickness considering a critical thickness. Then, we have carried out numerical simulations of a countercurrent flow in a vertical tube so as to investigate the CCFL characteristics and compare them with the previous experimental results. As a result, it has been concluded that the effect of liquid film entrainment by upward gas flux will cause the difference in the experiments.

  10. Three-field modeling with droplet entrainment and de-entrainment models for TRAC-M

    International Nuclear Information System (INIS)

    Lee, Sang Ik

    2005-02-01

    A three-field modeling has been developed and implemented to the basic one-dimensional components of TRAC-M/F90 (Modernized Transient Reactor Analysis Code, Fortran90) to improve the estimation of the behavior of droplet entrainment. the divide and conquer algorithmic technique is adjusted for the implementation after considering the verifications. The governing equations are composed of the conservation equations of each field with thermal-equilibrium assumption between the two liquid fields. As a result, three momentum equations, four mass equations including noncondensable gas mass equation and two energy equations are used. In the development of the momentum equation for an entrained droplet, two different kinds of approaches are tested: the simple force balance on a single droplet and the field-type equation based on the continuum assumption. The first showed unstable nature and the latter was chosen. All of the necessary empirical correlations were obtained from literatures, in particular, the physical models of COBRA-TF. The sensitivities of each empirical correlation were investigated where the effect of droplet diameter and droplet drag was found to be negligible. The advantages of the SETS numerical scheme in comparison with the semi-implicit nimerical scheme were addressed in the simulation time and the maximum allowed time-step size. Finally, the simulations of Collier and Hewitt's experiment were performed and it is concluded that the three-field model developed in the present study is reasonable. The predictions by the present code agree with the measured values within the RMS errors of 16.5% and 9.6% in the entrained liquid mass flow rates and the pressure gradients, respectively. Assessment on the physical models is performed. The wall and interfacial drag models were determined at first. After that, the assessments of entrainment model were performed. Wurtz's entrainment model, which was used in COBRA-TF and Kataoka and Ishii's model, were mainly

  11. Timescales of Massive Human Entrainment

    DEFF Research Database (Denmark)

    Fusaroli, Riccardo; Perlman, Marcus; Mislove, Alan

    2014-01-01

    of distinct scales, in an exquisitely time locked fashion. Using a large scale database of human communication data, we analyze and describe three different time scales of human entrainment in electronic media. We sought a distinct shared experience that provided a test bed for quantifying large scale human...

  12. ON THE CAUSE OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Cassak, P. A.; Shepherd, L. S.; Drake, J. F.; Gosling, J. T.; Phan, T.-D.; Shay, M. A.

    2013-01-01

    A model of supra-arcade downflows (SADs), dark low density regions also known as tadpoles that propagate sunward during solar flares, is presented. It is argued that the regions of low density are flow channels carved by sunward-directed outflow jets from reconnection. The solar corona is stratified, so the flare site is populated by a lower density plasma than that in the underlying arcade. As the jets penetrate the arcade, they carve out regions of depleted plasma density which appear as SADs. The present interpretation differs from previous models in that reconnection is localized in space but not in time. Reconnection is continuous in time to explain why SADs are not filled in from behind as they would if they were caused by isolated descending flux tubes or the wakes behind them due to temporally bursty reconnection. Reconnection is localized in space because outflow jets in standard two-dimensional reconnection models expand in the normal (inflow) direction with distance from the reconnection site, which would not produce thin SADs as seen in observations. On the contrary, outflow jets in spatially localized three-dimensional reconnection with an out-of-plane (guide) magnetic field expand primarily in the out-of-plane direction and remain collimated in the normal direction, which is consistent with observed SADs being thin. Two-dimensional proof-of-principle simulations of reconnection with an out-of-plane (guide) magnetic field confirm the creation of SAD-like depletion regions and the necessity of density stratification. Three-dimensional simulations confirm that localized reconnection remains collimated

  13. RE-INTERPRETATION OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Savage, Sabrina L.; McKenzie, David E.; Reeves, Katharine K.

    2012-01-01

    Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193 Å channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be 'side effects' of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations and on reconnection theory.

  14. RE-INTERPRETATION OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Savage, Sabrina L. [NASA/Goddard Space Flight Center (Oak Ridge Associated Universities), 8800 Greenbelt Rd Code 671, Greenbelt, MD 20771 (United States); McKenzie, David E. [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, MT 59717-3840 (United States); Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138 (United States)

    2012-03-10

    Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193 Angstrom-Sign channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be 'side effects' of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations and on reconnection theory.

  15. Experimental studies on spray and gas entrainment characteristics of biodiesel fuel: Implications of gas entrained and fuel oxygen content on soot formation

    International Nuclear Information System (INIS)

    Kuti, Olawole Abiola; Nishida, Keiya; Zhu, Jingyu

    2013-01-01

    Experiments were performed inside the constant volume vessel to simulate the real diesel engine conditions. The LIF–PIV (Laser Induced Florescence – Particulate Image Velocimetry) technique was used to characterize the spray and gas entrainment characteristics of the fuels while the OH-chemiluminescence and two color pyrometry were applied to obtain information about the combustion processes. Biodiesel from palm oil (BDF (Biodiesel Fuel)) and the JIS #2 diesel fuel were utilized. It was observed that the SMD (Sauter mean diameter) obtained through an empirical equation decreased by increasing the injection pressure from 100 to 300 MPa and reducing the nozzle diameter from 0.16 to 0.08 mm. BDF has higher SMD values compared to diesel thus signifying inferior atomization. By increasing the injection pressure up to 300 MPa and reducing the nozzle diameter to 0.08 mm, the normal velocity and total mass flow rate of the entrained gas by the fuels increased. Due to higher viscosity and density properties, BDF possessed inferior atomization characteristics which made the normal velocity and total mass flow rate of the entrained gas lower compared to diesel. Due to inferior atomization which led to less gas being entrained upstream of the lift-off flame, the fuel oxygen content in BDF played a significant role in soot formation processes. - Highlights: • Spray and gas entrainment characteristics of biodiesel (BDF (Biodiesel Fuel)) and fuel were investigated. • Effect of injector parameters on BDF spray and gas entrainment characteristics was identified. • Higher viscosity and density of BDF yielded inferior spray atomization processes. • Gas entrainment velocity and mass flow rate of gas entrained by BDF lower. • Gas entrained had less effect on BDF's soot formation

  16. A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, V. M. J.; Mathioudakis, M. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, Northern Ireland (United Kingdom); Socas-Navarro, H. [Instituto de Astrofísica de Canarias, Avda vía Láctea S/N, E-38205 La Laguna, Tenerife (Spain); Rodríguez, J. de la Cruz, E-mail: v.henriques@qub.ac.uk [Institute for Solar Physics, Department of Astronomy, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden)

    2017-08-20

    We perform non-LTE inversions in a large set of umbral flashes, including the dark fibrils visible within them, and in the quiescent umbra by using the inversion code NICOLE on a set of full Stokes high-resolution Ca ii λ 8542 observations of a sunspot at disk center. We find that the dark structures have Stokes profiles that are distinct from those of the quiescent and flashed regions. They are best reproduced by atmospheres that are more similar to the flashed atmosphere in terms of velocities, even if with reduced amplitudes. We also find two sets of solutions that finely fit the flashed profiles: a set that is upflowing, featuring a transition region that is deeper than in the quiescent case and preceded by a slight dip in temperature, and a second solution with a hotter atmosphere in the chromosphere but featuring downflows close to the speed of sound at such heights. Such downflows may be related, or even dependent, on the presence of coronal loops, rooted in the umbra of sunspots, as is the case in the region analyzed. Similar loops have been recently observed to have supersonic downflows in the transition region and are consistent with the earlier “sunspot plumes,” which were invariably found to display strong downflows in sunspots. Finally, we find, on average, a magnetic field reduction in the flashed areas, suggesting that the shock pressure is moving field lines in the upper layers.

  17. Measurements of air entrainment by vertical plunging liquid jets

    Science.gov (United States)

    El Hammoumi, M.; Achard, J. L.; Davoust, L.

    2002-06-01

    This paper addresses the issue of the air-entrainment process by a vertical plunging liquid jet. A non-dimensional physical analysis, inspired by the literature on the stability of free jets submitted to an aerodynamic interaction, was developed and yielded two correlation equations for the laminar and the turbulent plunging jets. These correlation equations allow the volumetric flow rate of the air carryunder represented by the Weber number of entrainment We n to be predicted. The plunging jets under consideration issued from circular tubes long enough to achieve a fully developed flow at the outlet. A sensitive technique based on a rising soap meniscus was developed to measure directly the volumetric flow rate of the air carryunder. Our data are compared with other experimental data available in the literature; they also stand as a possible database for future theoretical modelling.

  18. Measurements of air entrainment by vertical plunging liquid jets

    Energy Technology Data Exchange (ETDEWEB)

    El Hammoumi, M. [Faculte des Sciences et Techniques, Departement de Physique, Laboratoire de Mecanique Appliquee, Fes (Morocco); Achard, J.L.; Davoust, L. [Laboratoire des Ecoulements Geophysiques et Industriels (LEGI), Grenoble (France)

    2002-06-01

    This paper addresses the issue of the air-entrainment process by a vertical plunging liquid jet. A non-dimensional physical analysis, inspired by the literature on the stability of free jets submitted to an aerodynamic interaction, was developed and yielded two correlation equations for the laminar and the turbulent plunging jets. These correlation equations allow the volumetric flow rate of the air carryunder represented by the Weber number of entrainment We{sub n} to be predicted. The plunging jets under consideration issued from circular tubes long enough to achieve a fully developed flow at the outlet. A sensitive technique based on a rising soap meniscus was developed to measure directly the volumetric flow rate of the air carryunder. Our data are compared with other experimental data available in the literature; they also stand as a possible database for future theoretical modelling. (orig.)

  19. Turbulent entrainment across turbulent-nonturbulent interfaces in stably stratified mixing layers

    Science.gov (United States)

    Watanabe, T.; Riley, J. J.; Nagata, K.

    2017-10-01

    The entrainment process in stably stratified mixing layers is studied in relation to the turbulent-nonturbulent interface (TNTI) using direct numerical simulations. The statistics are calculated with the interface coordinate in an Eulerian frame as well as with the Lagrangian fluid particles entrained from the nonturbulent to the turbulent regions. The characteristics of entrainment change as the buoyancy Reynolds number Reb decreases and the flow begins to layer. The baroclinic torque delays the enstrophy growth of the entrained fluids at small Reb, while this effect is less efficient for large Reb. The entrained particle movement within the TNTI layer is dominated by the small dissipative scales, and the rapid decay of the kinetic energy dissipation rate due to buoyancy causes the entrained particle movement relative to the interface location to become slower. Although the Eulerian statistics confirm that there exists turbulent fluid with strong vorticity or with large buoyancy frequency near the TNTI, the entrained fluid particles circumvent these regions by passing through the TNTI in strain-dominant regions or in regions with small buoyancy frequency. The multiparticle statistics show that once the nonturbulent fluid volumes are entrained, they are deformed into flattened shapes in the vertical direction and diffuse in the horizontal direction. When Reb is large enough for small-scale turbulence to exist, the entrained fluid is able to penetrate into the turbulent core region. Once the flow begins to layer with decreasing Reb, however, the entrained fluid volume remains near the outer edge of the turbulent region and forms a stably stratified layer without vertical overturning.

  20. Impact of entrainment and impingement on fish populations in the Hudson River estuary. Volume I. Entrainment-impact estimates for six fish populations inhabiting the Hudson River estuary

    International Nuclear Information System (INIS)

    Boreman, J.; Barnthouse, L.W.; Vaughn, D.S.; Goodyear, C.P.; Christensen, S.W.; Kumar, K.D.; Kirk, B.L.; Van Winkle, W.

    1982-01-01

    This volume is concerned with the estimation of the direct (or annual) entrainment impact of power plants on populations of striped bass, white perch, Alosa spp. (blueback herring and alewife), American shad, Atlantic tomcod, and bay anchovy in the Hudson River estuary. Entrainment impact results from the killing of fish eggs, larvae, and young juveniles that are contained in the cooling water cycled through a power plant. An Empirical Transport Model (ETM) is presented as the means of estimating a conditional entrainment mortality rate (defined as the fraction of a year class which would be killed due to entrainment in the absence of any other source of mortality). Most of this volume is concerned with the estimation of several parameters required by the ETM: physical input parameters (e.g., power-plant withdrawal flow rates); the longitudinal distribution of ichthyoplankton in time and space; the duration of susceptibility of the vulnerable organisms; the W-factors, which express the ratios of densities of organisms in power plant intakes to densities of organisms in the river; and the entrainment mortality factors (f-factors), which express the probability that an organism will be killed if it is entrained. Once these values are obtained, the ETM is used to estimate entrainment impact for both historical and projected conditions

  1. Occurrence rate of ion upflow and downflow observed by the Poker Flat Incoherent Scatter Radar (PFISR)

    Science.gov (United States)

    Zou, S.; Lu, J.; Varney, R. H.

    2017-12-01

    This study aims to investigate the occurrence rate of ion upflow and downflow events in the auroral ionosphere, using a full 3-year (2011-2013) dataset collected by the Poker Flat Incoherent Scatter Radar (PFISR) at 65.5° magnetic latitude. Ion upflow and downflow events are defined if there are three consecutive data points larger/smaller than 100/-100 m/s in the ion field-aligned velocity altitude profile. Their occurrence rates have been evaluated as a function of magnetic local time (MLT), season, geomagnetic activity, solar wind and interplanetary magnetic field (IMF). We found that the ion upflows are twice more likely to occur on the nightside than the dayside, and have slightly higher occurrence rate near Fall equinox. In contrast, the ion downflow events are more likely to occur in the afternoon sector but also during Fall equinox. In addition, the occurrence rate of ion upflows on the nightside increases when the aurora electrojet index (AE) and planetary K index (Kp) increase, while the downflows measured on the dayside clearly increase as the AE and Kp increase. In general, the occurrence rate of ion upflows increases with enhanced solar wind and IMF drivers. This correlation is particularly strong between the upflows on the nightside and the solar wind dynamic pressure and IMF Bz. The lack of correlation of upflows on the dayside with these parameters is due to the location of PFISR, which is usually equatorward of the dayside auroral zone and within the nightside auroral zone under disturbed conditions. The occurrence rate of downflow at all MLTs does not show strong dependence on the solar wind and IMF conditions. However, it occurs much more frequently on the dayside when the IMF By is strongly positive, i.e., >10 nT and the IMF Bz is strongly negative, i.e., < -10 nT. We suggest that the increased occurrence rate of downflows on the dayside is associated with dayside storm-enhanced density and the plume.

  2. Crustal entrainment and pulsar glitches.

    Science.gov (United States)

    Chamel, N

    2013-01-04

    Large pulsar frequency glitches are generally interpreted as sudden transfers of angular momentum between the neutron superfluid permeating the inner crust and the rest of the star. Despite the absence of viscous drag, the neutron superfluid is strongly coupled to the crust due to nondissipative entrainment effects. These effects are shown to severely limit the maximum amount of angular momentum that can possibly be transferred during glitches. In particular, it is found that the glitches observed in the Vela pulsar require an additional reservoir of angular momentum.

  3. An applied model for the height of the daytime mixed layer and the entrainment zone

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    1994-01-01

    A model is presented for the height of the mixed layer and the depth of the entrainment zone under near-neutral and unstable atmospheric conditions. It is based on the zero-order mixed layer height model of Batchvarova and Gryning (1991) and the parameterization of the entrainment zone depth......-layer height: friction velocity, kinematic heat flux near the ground and potential temperature gradient in the free atmosphere above the entrainment zone. When information is available on the horizontal divergence of the large-scale flow field, the model also takes into account the effect of subsidence...

  4. Entrainer selection for the synthesis of fatty acid esters by entrainer-based reactive distillation

    NARCIS (Netherlands)

    Jong, de M.C.; Zondervan, E.; Dimian, A.C.; Haan, de A.B.

    2010-01-01

    In this research it is demonstrated that, due to the similarities between Entrainer-based Reactive Distillation and azeotropic distillation, the same selection rules can be applied to select a suitable entrainer. From a list of suitable entrainers for the azeotropic distillation of isopropanol and

  5. Visual cortex entrains to sign language.

    Science.gov (United States)

    Brookshire, Geoffrey; Lu, Jenny; Nusbaum, Howard C; Goldin-Meadow, Susan; Casasanto, Daniel

    2017-06-13

    Despite immense variability across languages, people can learn to understand any human language, spoken or signed. What neural mechanisms allow people to comprehend language across sensory modalities? When people listen to speech, electrophysiological oscillations in auditory cortex entrain to slow ([Formula: see text]8 Hz) fluctuations in the acoustic envelope. Entrainment to the speech envelope may reflect mechanisms specialized for auditory perception. Alternatively, flexible entrainment may be a general-purpose cortical mechanism that optimizes sensitivity to rhythmic information regardless of modality. Here, we test these proposals by examining cortical coherence to visual information in sign language. First, we develop a metric to quantify visual change over time. We find quasiperiodic fluctuations in sign language, characterized by lower frequencies than fluctuations in speech. Next, we test for entrainment of neural oscillations to visual change in sign language, using electroencephalography (EEG) in fluent speakers of American Sign Language (ASL) as they watch videos in ASL. We find significant cortical entrainment to visual oscillations in sign language sign is strongest over occipital and parietal cortex, in contrast to speech, where coherence is strongest over the auditory cortex. Nonsigners also show coherence to sign language, but entrainment at frontal sites is reduced relative to fluent signers. These results demonstrate that flexible cortical entrainment to language does not depend on neural processes that are specific to auditory speech perception. Low-frequency oscillatory entrainment may reflect a general cortical mechanism that maximizes sensitivity to informational peaks in time-varying signals.

  6. Neural Entrainment to Speech Modulates Speech Intelligibility

    NARCIS (Netherlands)

    Riecke, Lars; Formisano, Elia; Sorger, Bettina; Baskent, Deniz; Gaudrain, Etienne

    2018-01-01

    Speech is crucial for communication in everyday life. Speech-brain entrainment, the alignment of neural activity to the slow temporal fluctuations (envelope) of acoustic speech input, is a ubiquitous element of current theories of speech processing. Associations between speech-brain entrainment and

  7. High-resolution Observations of Downflows at One End of a Pre-eruption Filament

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qin; Deng, Na; Jing, Ju; Wang, Haimin, E-mail: ql47@njit.edu [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States)

    2017-06-01

    Studying the dynamics of filaments at the pre-eruption phase can shed light on the precursor of eruptive events. Such high-resolution studies (of the order of 0.″1) are highly desirable yet very rare. In this work, we present a detailed observation of a pre-eruption evolution of a filament obtained by the 1.6 m New Solar Telescope (NST) at the Big Bear Solar Observatory (BBSO). One end of the filament is anchored at the sunspot in the NOAA active region (AR) 11515, which is well observed by NST H α off-bands from four hours before to one hour after the filament eruption. A M1.6 flare is associated with the eruption. We observed persistent downflowing materials along the H α multi-threaded component of the loop toward the AR end during the pre-eruption phase. We traced the trajectories of plasma blobs along the H α threads and obtained a plane-of-sky velocity of 45 km s{sup −1} on average. Furthermore, we estimated the real velocities of the downflows and the altitude of the filament by matching the observed H α threads with magnetic field lines extrapolated from a nonlinear force-free field model. Observations of chromospheric brightenings at the footpoints of the falling plasma blobs are also presented. The lower limit of the kinetic energy per second of the downflows through the brightenings is found to be ∼10{sup 21} erg. Larger FOV observations from BBSO full-disk H α images show that the AR end of the filament started ascending four hours before the flare. We attribute the observed downflows at the AR end of the filament to the draining effect of the filament rising prior to its eruption. During the slow-rise phase, the downflows continuously drained away ∼10{sup 15}g mass from the filament over a few hours, which is believed to be essential for the instability, and could be an important precursor of eruptive events.

  8. Downflow limestone beds for treatment of net-acidic, oxic, iron-laden drainage from a flooded Anthracite Mine, Pennsylvania, USA: 1. Field evaluation

    Science.gov (United States)

    Cravotta, C.A.; Ward, S.J.

    2008-01-01

    Passive-treatment systems that route acidic mine drainage (AMD) through crushed limestone and/or organic-rich substrates have been used to remove the acidity and metals from various AMD sources, with a wide range of effects. This study evaluates treatment of net-acidic, oxic, iron-laden AMD with limestone alone, and with organic-rich compost layered with the limestone. In the fall of 2003, a treatment system consisting of two parallel, 500-m2 downflow cells followed by a 400-m2 aerobic settling pond and wetland was installed to neutralize the AMD from the Bell Mine, a large source of AMD and baseflow to the Schuylkill River in the Southern Anthracite Coalfield, in east-central Pennsylvania. Each downflow cell consisted of a lower substrate layer of 1,090 metric tons (t) of dolomitic limestone (60 wt% CaCO3) and an upper layer of 300 t of calcitic limestone (95 wt% CaCO3); one of the downflow cells also included a 0.3 m thick layer of mushroom compost over the limestone. AMD with pH of 3.5-4.3, dissolved oxygen of 6.6-9.9 mg/L, iron of 1.9-5.4 mg/L, and aluminum of 0.8-1.9 mg/L flooded each cell to a depth 0.65 m above the treatment substrates, percolated through the substrates to underlying, perforated outflow pipes, and then flowed through the aerobic pond and wetland before discharging to the Schuylkill River. Data on the flow rates and chemistry of the effluent for the treatment system indicated substantial neutralization by the calcitic limestone but only marginal effects from the dolomitic limestone or compost. Because of its higher transmissivity, the treatment cell containing only limestone neutralized greater quantities of acidity than the cell containing compost and limestone. On average, the treatment system removed 62% of the influent acidity, 47% of the dissolved iron, 34% of the dissolved aluminum, and 8% of the dissolved manganese. Prior to treatment of the Bell Discharge, the Schuylkill River immediately below its confluence with the discharge had p

  9. Combination downflow-upflow vapor-liquid separator

    Energy Technology Data Exchange (ETDEWEB)

    Kidwell, John H. (Uniontown, OH); Prueter, William P. (Alliance, OH); Eaton, Andrew M. (Alliance, OH)

    1987-03-10

    An improved vapor-liquid separator having a vertically disposed conduit for flow of a mixture. A first, second and third plurality of curved arms penetrate and extend within the conduit. A cylindrical member is radially spaced from the conduit forming an annulus therewith and having perforations and a retaining lip at its upper end.

  10. Combination downflow-upflow vapor-liquid separator

    Energy Technology Data Exchange (ETDEWEB)

    Kidwell, J.H.; Prueter, W.P.; Eaton, A.M.

    1987-03-10

    An improved vapor-liquid separator is described having a vertically disposed conduit for flow of a mixture. A first, second and third plurality of curved arms penetrate and extend within the conduit. A cylindrical member is radially spaced from the conduit forming an annulus therewith and having perforations and a retaining lip at its upper end. 11 figs.

  11. Entrainment of droplets during the reflood phase of a LOCA and the influence of the channel geometry

    International Nuclear Information System (INIS)

    van der Molen, S.B.; Galjee, F.W.B.M.

    1979-01-01

    This paper describes the different reflood phenomena and the most relevant appearing two phase flow patterns such as the inverted annular, the annular and dispersed flow regimes and the transition between the different regimes. From high speed films it is clear that the onset of entrainment in case of the liquid column type quench mode occurs simultaneously with the transition of churn flow to a dispersed flow whereas in case of the dryout type quench mode with an annular flow at the quench front, the onset of entrainment is caused by the interaction of the vapor flow on the liquid film flow. 14 refs

  12. Temperature compensation and entrainment in circadian rhythms

    International Nuclear Information System (INIS)

    Bodenstein, C; Heiland, I; Schuster, S

    2012-01-01

    To anticipate daily variations in the environment and coordinate biological activities into a daily cycle many organisms possess a circadian clock. In the absence of external time cues the circadian rhythm persists with a period of approximately 24 h. The clock phase can be shifted by single pulses of light, darkness, chemicals, or temperature and this allows entrainment of the clock to exactly 24 h by cycles of these zeitgebers. On the other hand, the period of the circadian rhythm is kept relatively constant within a physiological range of constant temperatures, which means that the oscillator is temperature compensated. The mechanisms behind temperature compensation and temperature entrainment are not fully understood, neither biochemically nor mathematically. Here, we theoretically investigate the interplay of temperature compensation and entrainment in general oscillatory systems. We first give an analytical treatment for small temperature shifts and derive that every temperature-compensated oscillator is entrainable to external small-amplitude temperature cycles. Temperature compensation ensures that this entrainment region is always centered at the endogenous period regardless of possible seasonal temperature differences. Moreover, for small temperature cycles the entrainment region of the oscillator is potentially larger for rectangular pulses. For large temperature shifts we numerically analyze different circadian clock models proposed in the literature with respect to these properties. We observe that for such large temperature shifts sinusoidal or gradual temperature cycles allow a larger entrainment region than rectangular cycles. (paper)

  13. Onset of liquid droplet entrainment on a direct vessel injection system for APR1400

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-sol; Lee, Jae-Young [Handong Global University, Pohang (Korea, Republic of); Kim, Jong-Rok; Euh, Dong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this research, a series of visualization works was conducted to understand droplet entrainment of the flow pattern generated in direct vessel injection system(DVI) of Korea nuclear power plant, APR 1400. In the emergency situation of a nuclear power plant, reliability of DVI cooling can be an important issue. It is known that, the amount and the rate of entrainment during the DVI cooling process can significantly affect the total heat removal. To visualize the film Reynolds number closely related with onset of droplet entrainment induced by falling film flow and lateral air flow in a small gap, confocal chromatic sensing method for measuring accurately film thickness and depth averaging particle image velocimetry for film velocity were used. The results have been post processed 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. To visualize the droplet entrainment induced by falling film flow and lateral air flow in a small gap, shadowgraph method with CCD camera (2200fps, 1280 pixel X 800 pixel, ) on coated plate with super water-repellent agent was used. The results have been post processed using 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. By adopting both super hydrophobic coating method and shadowgraph method, entrainment in a narrow gap was successfully visualized that has rarely performed before and meaningful results for DVI system research fields have been made.

  14. Onset of liquid droplet entrainment on a direct vessel injection system for APR1400

    International Nuclear Information System (INIS)

    Kim, Han-sol; Lee, Jae-Young; Kim, Jong-Rok; Euh, Dong-Jin

    2016-01-01

    In this research, a series of visualization works was conducted to understand droplet entrainment of the flow pattern generated in direct vessel injection system(DVI) of Korea nuclear power plant, APR 1400. In the emergency situation of a nuclear power plant, reliability of DVI cooling can be an important issue. It is known that, the amount and the rate of entrainment during the DVI cooling process can significantly affect the total heat removal. To visualize the film Reynolds number closely related with onset of droplet entrainment induced by falling film flow and lateral air flow in a small gap, confocal chromatic sensing method for measuring accurately film thickness and depth averaging particle image velocimetry for film velocity were used. The results have been post processed 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. To visualize the droplet entrainment induced by falling film flow and lateral air flow in a small gap, shadowgraph method with CCD camera (2200fps, 1280 pixel X 800 pixel, ) on coated plate with super water-repellent agent was used. The results have been post processed using 4G Insight software. By measuring two dimensional film Reynolds number, we can predict the onset of droplet entrainment and obtain visible breakup region intuitively. By adopting both super hydrophobic coating method and shadowgraph method, entrainment in a narrow gap was successfully visualized that has rarely performed before and meaningful results for DVI system research fields have been made

  15. Pulsing flow in trickle bed columns

    NARCIS (Netherlands)

    Blok, Jan Rudolf

    1981-01-01

    In the operation of a packed column with cocurrent downflow of gas and liquid (trickle bed) several flowpatterns can be observed depending on the degree of interaction between gas and liquid. At low liquid and gas flow rates - low interaction - gascontinuous flow occurs. In this flowregime, the

  16. Note On The Ross Sea Shelf Water Downflow Processes (antarctica)

    Science.gov (United States)

    Bergamasco, A.; Defendi, V.; Spezie, G.; Budillon, G.; Carniel, S.

    In the framework of the CLIMA Project of the Italian National Program for Research in Antarctica, three different experimental data sets were acquired along the continental shelf break; two of them (in 1997 and 2001) close to Cape Adare, the 1998 one in the middle of the Ross Sea (i.e. 75 S, 177 W). The investigations were chosen in order to explore the downslope flow of the bottom waters produced in the Ross Sea, namely the High Salinity Shelf Water (HSSW, the densest water mass of the southern ocean coming from its formation site in the polynya region in Terra Nova bay), and the Ice Shelf Water (ISW, originated below the Ross Ice Shelf and outflowing northward). Both bottom waters spill over the shelf edge and mix with the Circumpolar Deep Water (CDW) contributing to the formation of the Antarctic Bottom Waters (AABW). Interpreting temperature, salinity and density maps in terms of cascading processes, both HSSW and ISW overflows are evidenced during, respectively, 1997 and 1998. During the 2001 acquisition there is no presence of HSSW along the shelf break, nevertheless distribution captures the evidence of a downslope flow process.

  17. Entraining the Brain: Applications to Language Research and Links to Musical Entrainment

    Directory of Open Access Journals (Sweden)

    Usha Goswami

    2012-09-01

    Full Text Available Clayton’s paper provides a clear and accessible summary of the significance of entrainment for music making, and for human behaviour in general. He notes the central role of metrical structure in musical entrainment, the possible role of oscillatory neural activity, and the core notion of phase alignment. Here I show how these same factors are central to speech processing by the human brain. I argue that entrainment to metrical structure is core to linguistic as well as musical human behaviour. I illustrate this view using entrainment data from developmental dyslexia. The core role of entrainment in efficient speech processing suggests that language difficulties in childhood may benefit from music-based remediation that focuses on multi-modal rhythmic entrainment. Alignment of linguistic and musical metrical structure seems likely to be fundamental to successful remediation.

  18. Cloud-Top Entrainment in Stratocumulus Clouds

    Science.gov (United States)

    Mellado, Juan Pedro

    2017-01-01

    Cloud entrainment, the mixing between cloudy and clear air at the boundary of clouds, constitutes one paradigm for the relevance of small scales in the Earth system: By regulating cloud lifetimes, meter- and submeter-scale processes at cloud boundaries can influence planetary-scale properties. Understanding cloud entrainment is difficult given the complexity and diversity of the associated phenomena, which include turbulence entrainment within a stratified medium, convective instabilities driven by radiative and evaporative cooling, shear instabilities, and cloud microphysics. Obtaining accurate data at the required small scales is also challenging, for both simulations and measurements. During the past few decades, however, high-resolution simulations and measurements have greatly advanced our understanding of the main mechanisms controlling cloud entrainment. This article reviews some of these advances, focusing on stratocumulus clouds, and indicates remaining challenges.

  19. Investigations of gas entrainment in KNK II

    International Nuclear Information System (INIS)

    Hoppe, P.; Massier, H.; Mitzel, F.; Vaeth, W.

    1979-08-01

    During commissioning of KNK II operational difficulties were encountered due to gas entrainment in the coolant. This gas entrainment caused negative reactivity fluctuations which tripped the reactor repeatedly. Since first investigations indicated one main cause of the gas entrainment and the existence of an accumulation process, a technical modification (installation of a throttle valve) for remedy was performed. This report describes the investigations made after the plant modification. The main objective was to test the effectiveness of the modifications and to look into the following still open problems: Localization of the gas storage, detection and estimation of a permanent gas entrainment and the analysis of positive power overshoots being observed in connection with the gas bubbles

  20. Entrainment: an annotated bibliography. Interim report

    International Nuclear Information System (INIS)

    Carrier, R.F.; Hannon, E.H.

    1979-04-01

    The 604 annotated references in this bibliography on the effects of pumped entrainment of aquatic organisms through the cooling systems of thermal power plants were compiled from published and unpublished literature and cover the years 1947 through 1977. References to published literature were obtained by searching large-scale commercial data bases, ORNL in-house-generated data bases, relevant journals, and periodical bibliographies. The unpublished literature is a compilation of Sections 316(a) and 316(b) demonstrations, environmental impact statements, and environmental reports prepared by the utilities in compliance with Federal Water Pollution Control Administration regulations. The bibliography includes references on monitoring studies at power plant sites, laboratory studies of physical and biological effects on entrained organisms, engineering strategies for the mitigation of entrainment effects, and selected theoretical studies concerned with the methodology for determining entrainment effects

  1. Enhancement of the anaerobic hydrolysis and fermentation of municipal solid waste in leachbed reactors by varying flow direction during water addition and leachate recycle

    Energy Technology Data Exchange (ETDEWEB)

    Uke, Matthew N., E-mail: cnmnu@leeds.ac.uk [Department of Civil Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Stentiford, Edward [Department of Civil Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2013-06-15

    Highlights: ► Combined downflow and upflow water addition improved hydraulic conductivity. ► Upflow water addition unclogged perforated screen leading to more leachate flow. ► The volume of water added and transmitted positively correlated with hydrolysis process. ► Combined downflow and upflow water addition increased COD production and yield. ► Combined downflow and upflow leachate recycle improved leachate and COD production. - Abstract: Poor performance of leachbed reactors (LBRs) is attributed to channelling, compaction from waste loading, unidirectional water addition and leachate flow causing reduced hydraulic conductivity and leachate flow blockage. Performance enhancement was evaluated in three LBRs M, D and U at 22 ± 3 °C using three water addition and leachate recycle strategies; water addition was downflow in D throughout, intermittently upflow and downflow in M and U with 77% volume downflow in M, 54% volume downflow in U while the rest were upflow. Leachate recycle was downflow in D, alternately downflow and upflow in M and upflow in U. The strategy adopted in U led to more water addition (30.3%), leachate production (33%) and chemical oxygen demand (COD) solubilisation (33%; 1609 g against 1210 g) compared to D (control). The total and volatile solids (TS and VS) reductions were similar but the highest COD yield (g-COD/g-TS and g-COD/g-VS removed) was in U (1.6 and 1.9); the values were 1.33 and 1.57 for M, and 1.18 and 1.41 for D respectively. The strategy adopted in U showed superior performance with more COD and leachate production compared to reactors M and D.

  2. Entrainment, transport and deposition of sediment by saline gravity currents

    Science.gov (United States)

    Zordan, Jessica; Juez, Carmelo; Schleiss, Anton J.; Franca, Mário J.

    2018-05-01

    Few studies have addressed simultaneously the feedback between the hydrodynamics of a gravity current and the geomorphological changes of a mobile bed. Hydrodynamic quantities such as turbulent and mean velocities, bed shear stress and turbulent stresses undoubtedly govern the processes of entrainment, transport and deposition. On the other hand, the incorporation of entrained sediment in the current may change its momentum by introducing extra internal stresses, introducing thus a feedback process. These two main questions are here investigated. Laboratory experiments of saline gravity currents, produced by lock-exchange, flowing over a mobile bed channel reach, are here reported. Different initial buoyancies of the current in the lock are tested together with three different grain sizes of the non-coherent sediment that form the erodible bed. Results from velocity measurements are combined with the visualization of the sediment movement in the mobile reach and with post-test topographic and photo surveys of the geomorphology modifications of the channel bed. Mean and turbulent velocities are measured and bed shear stress and Reynolds stresses are estimated. We show that the mean vertical component of the velocity and bed shear stress are highly correlated with the first instants of sediment entrainment. Vertical turbulent velocity is similarly related to entrainment, although with lower correlation values, contributing as well to the sediment movement. Bed shear stress and Reynolds shear stress measured near the bed are correlated with sediment entrainment for longer periods, indicating that these quantities are associated to distal transport as well. Geomorphological changes in the mobile bed are strongly related to the impulse caused by the bed shear stress on the sediment. On the other hand, we show that the nature of the grain of the mobile bed reach influences the hydrodynamics of the current which means that a feedback mechanisms between both occurs during

  3. MHD SIMULATIONS OF CORONAL SUPRA-ARCADE DOWNFLOWS INCLUDING ANISOTROPIC THERMAL CONDUCTION

    International Nuclear Information System (INIS)

    Zurbriggen, E.; Costa, A.; Schneiter, M.; Cécere, M.; Esquivel, A.

    2016-01-01

    Coronal supra-arcade downflows (SADs) are observed as dark trails descending toward hot turbulent-fan-shaped regions. Due to the large temperature values and gradients in these fan regions, the thermal conduction (TC) should be very efficient. While several models have been proposed to explain the triggering and the evolution of SADs, none of these scenarios address a systematic consideration of TC. Thus, we accomplish this task numerically simulating the evolution of SADs within this framework. That is, SADs are conceived as voided (subdense) cavities formed by nonlinear waves triggered by downflowing bursty localized reconnection events in a perturbed hot fan. We generate a properly turbulent fan, obtained by a stirring force that permits control of the energy and vorticity input in the medium where SADs develop. We include anisotropic TC and consider plasma properties consistent with observations. Our aim is to study whether it is possible to prevent SADs from vanishing by thermal diffusion. We find that this will be the case, depending on the turbulence parameters, in particular if the magnetic field lines are able to envelope the voided cavities, thermally isolating them from the hot environment. Velocity shear perturbations that are able to generate instabilities of the Kelvin–Helmholtz type help to produce magnetic islands, extending the lifetime of SADs.

  4. DETECTION OF SUPERSONIC DOWNFLOWS AND ASSOCIATED HEATING EVENTS IN THE TRANSITION REGION ABOVE SUNSPOTS

    Energy Technology Data Exchange (ETDEWEB)

    Kleint, L.; Martínez-Sykora, J. [Bay Area Environmental Research Institute, 625 2nd Street, Ste. 209, Petaluma, CA (United States); Antolin, P. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Tian, H.; Testa, P.; Reeves, K. K.; McKillop, S.; Saar, S.; Golub, L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Judge, P. [High Altitude Observatory/NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); De Pontieu, B.; Wuelser, J. P.; Boerner, P.; Hurlburt, N.; Lemen, J.; Tarbell, T. D.; Title, A. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover St., Org. ADBS, Bldg. 252, Palo Alto, CA 94304 (United States); Carlsson, M.; Hansteen, V. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Jaeggli, S., E-mail: lucia.kleint@fhnw.ch [Department of Physics, Montana State University, Bozeman, P.O. Box 173840, Bozeman, MT 59717 (United States); and others

    2014-07-10

    Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0.''33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km s{sup –1} and weaker, slightly slower upflows in the spectral lines Mg II h and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated with brightenings in the slitjaw images (SJIs). The bursty behavior lasts throughout the 2 hr observation, with average burst durations of about 20 s. The locations of these short-lived events appear to be the umbral and penumbral footpoints of EUV loops. Fast apparent downflows are observed along these loops in the SJIs and in the Atmospheric Imaging Assembly, suggesting that the loops are thermally unstable. We interpret the observations as cool material falling from coronal heights, and especially coronal rain produced along the thermally unstable loops, which leads to an increase of intensity at the loop footpoints, probably indicating an increase of density and temperature in the TR. The rain speeds are on the higher end of previously reported speeds for this phenomenon, and possibly higher than the free-fall velocity along the loops. On other observing days, similar bright dots are sometimes aligned into ribbons, resembling small flare ribbons. These observations provide a first insight into small-scale heating events in sunspots in the TR.

  5. Supra Arcade Downflows with XRT Informed by Dipolarization Fronts with THEMIS

    Science.gov (United States)

    Kobelski, Adam; Savage, Sabrina L.; Malaspina, David M.

    2016-01-01

    Magnetic reconnection can rapidly reconfigure the magnetic field of the corona, accelerating plasma through the site of reconnection. Ambiguities due to the nature of remote sensing have complicated the interpretation of observations of the inflowing and outflowing plasma in reconnecting regions. In particular, the interpretation of sunward moving density depletions above flare arcades (known as Supra Arcade Downflows - SADs) is still debated. Hinode/XRT has provided a wealth of observations for SADs and helped inform our current understanding of these structures. SADs have been interpreted as wakes behind newly reconnected and outflowing loops (Supra Arcade Downflowing Loops - SADLs). Models have shown the plausibility of this interpretation, though this interpretation has not yet been fully accepted. We present here observations of newly reconnected outflowing loops observed via in situ instruments in the magnetosphere. These observations, provided by five THEMIS spacecraft, show that around retracting loops (dipolarization fronts in this context) similar dynamic temperature and density structures are found as seen in SADs. We compare data from multiple SADs and dipolarization fronts to show that the observational signatures implied in the corona can be directly observed in similar plasma regimes in the magnetosphere, strongly favoring the interpretation of SADs as wakes behind retracting loops.

  6. MHD SIMULATIONS OF CORONAL SUPRA-ARCADE DOWNFLOWS INCLUDING ANISOTROPIC THERMAL CONDUCTION

    Energy Technology Data Exchange (ETDEWEB)

    Zurbriggen, E.; Costa, A.; Schneiter, M.; Cécere, M. [Instituto de Investigaciones en Astronomía Teórica y Experimental (IATE), Córdoba (Argentina); Esquivel, A., E-mail: ezurbriggen@unc.edu.ar, E-mail: acosta@unc.edu.ar [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México (Mexico)

    2016-11-20

    Coronal supra-arcade downflows (SADs) are observed as dark trails descending toward hot turbulent-fan-shaped regions. Due to the large temperature values and gradients in these fan regions, the thermal conduction (TC) should be very efficient. While several models have been proposed to explain the triggering and the evolution of SADs, none of these scenarios address a systematic consideration of TC. Thus, we accomplish this task numerically simulating the evolution of SADs within this framework. That is, SADs are conceived as voided (subdense) cavities formed by nonlinear waves triggered by downflowing bursty localized reconnection events in a perturbed hot fan. We generate a properly turbulent fan, obtained by a stirring force that permits control of the energy and vorticity input in the medium where SADs develop. We include anisotropic TC and consider plasma properties consistent with observations. Our aim is to study whether it is possible to prevent SADs from vanishing by thermal diffusion. We find that this will be the case, depending on the turbulence parameters, in particular if the magnetic field lines are able to envelope the voided cavities, thermally isolating them from the hot environment. Velocity shear perturbations that are able to generate instabilities of the Kelvin–Helmholtz type help to produce magnetic islands, extending the lifetime of SADs.

  7. Entrainment Zone Characteristics and Entrainment Rates in Cloud-Topped Boundary Layers from DYCOMS-II

    Science.gov (United States)

    2012-03-01

    Malinowski , J. L. Brenguier, and F. Burnet, 2005: Holes and entrainment in stratocumulus. J. Atmos. Sci., 62, 443–459. Glickman, T. S...of the Entrainment Zone in Cloud-topped Boundary Layers. Department of Meteorology, NPS, 93 pp. Krzysztof, Haman E., S. P. Malinowski , M. J

  8. PTV analysis of the entrained air into the diesel spray at high-pressure injection

    Science.gov (United States)

    Toda, Naoki; Yamashita, Hayato; Mashida, Makoto

    2014-08-01

    In order to clarify the effect of high-pressure injection on soot reduction in terms of the air entrainment into spray, the air flow surrounding the spray and set-off length indicating the distance from the nozzle tip to the flame region in diffusion diesel combustion were investigated using 300MPa injection of a multi-hole injector. The measurement of the air entrainment flow was carried out at non-evaporating condition using consecutive PTV (particle tracking velocimetry) method with a high-speed camera and a high-frequency pulse YAG laser. The set-off length was measured at highpressure and high-temperature using the combustion bomb of constant volume and optical system of shadow graph method. And the amount of air entrainment into spray until reaching set-off length in diffusion combustion was studied as a factor of soot formation.

  9. HAZARDOUS WASTE INCINERATION: THE IN-SITU CAPTURE OF LEAD BY SORBENTS IN A LABORATORY DOWNFLOW COMBUSTOR

    Science.gov (United States)

    The paper discusses experiments on a 17-kW downflow combustor to determine how sorbent injection into the postflame influenced the particle size distribution of a lead (Pb) aerosol formed from a surrogate Pb-containing waste. n the absence of chlorine (CI), the Pb aerosol size di...

  10. A Downflow Hanging Sponge (DHS) reactor for faecal coliform removal from an Upflow Anaerobic Sludge Bed (UASB) effluent

    NARCIS (Netherlands)

    Yaya Beas, R.E.; Kujawa-Roeleveld, K.; Lier, van J.B.; Zeeman, G.

    2015-01-01

    This research was conducted to study the faecal coliforms removal capacity of Downflow Hanging Sponge (DHS) reactors as a post-treatment for an Upflow Anaerobic Sludge Blanket (UASB) reactor. Three long-term continuous lab-scale DHS reactors i.e. a reactor with cube type sponges without

  11. Inclined gravity currents filling basins: The influence of Reynolds number on entrainment into gravity currents

    Science.gov (United States)

    Hogg, Charlie A. R.; Dalziel, Stuart B.; Huppert, Herbert E.; Imberger, Jörg

    2015-09-01

    In many important natural and industrial systems, gravity currents of dense fluid feed basins. Examples include lakes fed by dense rivers and auditoria supplied with cooled air by ventilation systems. As we will show, the entrainment into such buoyancy driven currents can be influenced by viscous forces. Little work, however, has examined this viscous influence and how entrainment varies with the Reynolds number, Re. Using the idea of an entrainment coefficient, E, we derive a mathematical expression for the rise of the front at the top of the dense fluid ponding in a basin, where the horizontal cross-sectional area of the basin varies linearly with depth. We compare this expression to experiments on gravity currents with source Reynolds numbers, Res, covering the broad range 100 < Res < 1500. The form of the observed frontal rises was well approximated by our theory. By fitting the observed frontal rises to the theoretical form with E as the free parameter, we find a linear trend for E(Res) over the range 350 < Res < 1100, which is in the transition to turbulent flow. In the experiments, the entrainment coefficient, E, varied from 4 × 10-5 to 7 × 10-2. These observations show that viscous damping can be a dominant influence on gravity current entrainment in the laboratory and in geophysical flows in this transitional regime.

  12. Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows

    Science.gov (United States)

    McKenzie, D.; Savage, S.

    2011-01-01

    The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.

  13. Air entrainment by plunging water jets

    NARCIS (Netherlands)

    Van de Sande, E.

    1974-01-01

    Gas entrainment caused by the impact of liquid jets upon liquid pool surfaces is a subject which has received too little attention. This well-known phenomenon,which occurs In nature and in numerous industrial operations, has only recently received interest from scientific workers. The influence on

  14. An experimental study of particle-driven gravity currents on steep slopes with entrainment of particles

    Directory of Open Access Journals (Sweden)

    M. Rastello

    2002-01-01

    Full Text Available Results of laboratory experiments are presented in which a finite suspension of sawdust particles was released instantaneously into a rectangular channel immersed in a water tank. Two kinds of gravity currents were studied: currents with or without entrainment of particles from the bed. Experiments were repeated for two slopes: 30° and 45°. We observed that the velocity of the front was significantly in-creased as particle entrainment occurred. In addition, our experiments showed that the front kept a quasi-constant velocity for both runs. This might suggest that the flow regime corresponded to the "slumping regime" or "adjustment phase" described earlier by Huppert and Simpson (1980.

  15. Speech Entrainment Compensates for Broca's Area Damage

    Science.gov (United States)

    Fridriksson, Julius; Basilakos, Alexandra; Hickok, Gregory; Bonilha, Leonardo; Rorden, Chris

    2015-01-01

    Speech entrainment (SE), the online mimicking of an audiovisual speech model, has been shown to increase speech fluency in patients with Broca's aphasia. However, not all individuals with aphasia benefit from SE. The purpose of this study was to identify patterns of cortical damage that predict a positive response SE's fluency-inducing effects. Forty-four chronic patients with left hemisphere stroke (15 female) were included in this study. Participants completed two tasks: 1) spontaneous speech production, and 2) audiovisual SE. Number of different words per minute was calculated as a speech output measure for each task, with the difference between SE and spontaneous speech conditions yielding a measure of fluency improvement. Voxel-wise lesion-symptom mapping (VLSM) was used to relate the number of different words per minute for spontaneous speech, SE, and SE-related improvement to patterns of brain damage in order to predict lesion locations associated with the fluency-inducing response to speech entrainment. Individuals with Broca's aphasia demonstrated a significant increase in different words per minute during speech entrainment versus spontaneous speech. A similar pattern of improvement was not seen in patients with other types of aphasia. VLSM analysis revealed damage to the inferior frontal gyrus predicted this response. Results suggest that SE exerts its fluency-inducing effects by providing a surrogate target for speech production via internal monitoring processes. Clinically, these results add further support for the use of speech entrainment to improve speech production and may help select patients for speech entrainment treatment. PMID:25989443

  16. Effect of flow leakage on the benchmarking of FLOWTRAN with Mark-22 mockup flow excursion test data from Babcock and Wilcox

    International Nuclear Information System (INIS)

    Chen, Kuo-Fu.

    1992-10-01

    This report presents a revised analysis of the Babcock and Wilcox (B and W) downflow flow excursion tests that accounts for leakage between flow channels in the test assembly. Leak rates were estimated by comparing results from the downflow tests with those for upflow tests conducted using an identical assembly with some minor modifications. The upflow test assembly did not contain leaks. This revised analyses shows that FLOWTRAN with the SRS working criterion conservatively predicts onset of flow instability without using a local peaking factor to model heat transfer variations near the ribs

  17. Noninvasive CPAP with face mask: comparison among new air-entrainment masks and the Boussignac valve.

    Science.gov (United States)

    Mistraletti, Giovanni; Giacomini, Matteo; Sabbatini, Giovanni; Pinciroli, Riccardo; Mantovani, Elena S; Umbrello, Michele; Palmisano, Debora; Formenti, Paolo; Destrebecq, Anne L L; Iapichino, Gaetano

    2013-02-01

    The performances of 2 noninvasive CPAP systems (high flow and low flow air-entrainment masks) were compared to the Boussignac valve in 3 different scenarios. Scenario 1: pneumatic lung simulator with a tachypnea pattern (tidal volume 800 mL at 40 breaths/min). Scenario 2: Ten healthy subjects studied during tidal breaths and tachypnea. Scenario 3: Twenty ICU subjects enrolled for a noninvasive CPAP session. Differences between set and effective CPAP level and F(IO(2)), as well as the lowest airway pressure and the pressure swing around the imposed CPAP level, were analyzed. The lowest airway pressure and swing were correlated to the pressure-time product (area of the airway pressure curve below the CPAP level) measured with the simulator. P(aO(2)) was a subject's further performance index. Lung simulator: Boussignac F(IO(2)) was 0.54, even if supplied with pure oxygen. The air-entrainment masks had higher swing than the Boussignac (P = .007). Pressure-time product correlated better with pressure swing (Spearman correlation coefficient [ρ] = 0.97) than with lowest airway pressure (ρ = 0.92). In healthy subjects, the high-flow air-entrainment mask showed lower difference between set and effective F(IO(2)) (P mask had lower swing than the Boussignac valve (P = .03) with similar P(aO(2)) increase. High-flow air-entrainment mask showed the best performance in human subjects. During high flow demand, the Boussignac valve delivered lower than expected F(IO(2)) and showed higher dynamic hyper-pressurization than the air-entrainment masks. © 2013 Daedalus Enterprises.

  18. Experimental investigations on a common centrifugal pump operating under gas entrainment conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schäfer, Thomas, E-mail: thomas.schaefer@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (Germany); Neumann, Martin [Technische Universität Dresden, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering (Germany); Bieberle, André [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (Germany); Hampel, Uwe [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (Germany); Technische Universität Dresden, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering (Germany)

    2017-05-15

    Highlights: • The pump performance has been evaluated for several gas entrainment conditions. • The gas entraining flow regime has a large impact on the pump performance. • High-resolution gamma-ray computed tomography (HireCT) has been applied. • Gas holdup inside the operating impeller has been visualized and quantified. • Gas holdup profiles along selected streamlines have been calculated. - Abstract: This paper presents an experimental study on the effects of additional gas entrainment in centrifugal pumps designed for conveying liquid phases only. The pump performance has been evaluated for several gas entrainment conditions, and for various operational settings of the pump, such as its alignment and the rotational speed of the impeller. As a main performance indicator the impact of entrained gas on the hydraulic power of the pump has been analyzed using experimental data. Additionally, high-resolution gamma-ray computed tomography (HireCT) operated in time-averaged rotation-synchronized scanning mode has been applied to quantify local phase fraction distributions inside the rapidly rotating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation areas inside the impeller chambers have been visualized. Thus, various internally accumulated gas holdup patterns have been identified and, eventually, associated with characteristic pump performance behaviors. Moreover, the tomographic measuring method allowed an enhanced gas holdup analysis in specified pump compartments. As a result, the related specific gas and liquid phase holdup profiles have been evaluated.

  19. Experimental investigations on a common centrifugal pump operating under gas entrainment conditions

    International Nuclear Information System (INIS)

    Schäfer, Thomas; Neumann, Martin; Bieberle, André; Hampel, Uwe

    2017-01-01

    Highlights: • The pump performance has been evaluated for several gas entrainment conditions. • The gas entraining flow regime has a large impact on the pump performance. • High-resolution gamma-ray computed tomography (HireCT) has been applied. • Gas holdup inside the operating impeller has been visualized and quantified. • Gas holdup profiles along selected streamlines have been calculated. - Abstract: This paper presents an experimental study on the effects of additional gas entrainment in centrifugal pumps designed for conveying liquid phases only. The pump performance has been evaluated for several gas entrainment conditions, and for various operational settings of the pump, such as its alignment and the rotational speed of the impeller. As a main performance indicator the impact of entrained gas on the hydraulic power of the pump has been analyzed using experimental data. Additionally, high-resolution gamma-ray computed tomography (HireCT) operated in time-averaged rotation-synchronized scanning mode has been applied to quantify local phase fraction distributions inside the rapidly rotating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation areas inside the impeller chambers have been visualized. Thus, various internally accumulated gas holdup patterns have been identified and, eventually, associated with characteristic pump performance behaviors. Moreover, the tomographic measuring method allowed an enhanced gas holdup analysis in specified pump compartments. As a result, the related specific gas and liquid phase holdup profiles have been evaluated.

  20. Large-scale Flow and Transport of Magnetic Flux in the Solar ...

    Indian Academy of Sciences (India)

    tribpo

    Abstract. Horizontal large-scale velocity field describes horizontal displacement of the photospheric magnetic flux in zonal and meridian directions. The flow systems of solar plasma, constructed according to the velocity field, create the large-scale cellular-like patterns with up-flow in the center and the down-flow on the ...

  1. Entrainment to periodic initiation and transition rates in a computational model for gene translation.

    Directory of Open Access Journals (Sweden)

    Michael Margaliot

    Full Text Available Periodic oscillations play an important role in many biomedical systems. Proper functioning of biological systems that respond to periodic signals requires the ability to synchronize with the periodic excitation. For example, the sleep/wake cycle is a manifestation of an internal timing system that synchronizes to the solar day. In the terminology of systems theory, the biological system must entrain or phase-lock to the periodic excitation. Entrainment is also important in synthetic biology. For example, connecting several artificial biological systems that entrain to a common clock may lead to a well-functioning modular system. The cell-cycle is a periodic program that regulates DNA synthesis and cell division. Recent biological studies suggest that cell-cycle related genes entrain to this periodic program at the gene translation level, leading to periodically-varying protein levels of these genes. The ribosome flow model (RFM is a deterministic model obtained via a mean-field approximation of a stochastic model from statistical physics that has been used to model numerous processes including ribosome flow along the mRNA. Here we analyze the RFM under the assumption that the initiation and/or transition rates vary periodically with a common period T. We show that the ribosome distribution profile in the RFM entrains to this periodic excitation. In particular, the protein synthesis pattern converges to a unique periodic solution with period T. To the best of our knowledge, this is the first proof of entrainment in a mathematical model for translation that encapsulates aspects such as initiation and termination rates, ribosomal movement and interactions, and non-homogeneous elongation speeds along the mRNA. Our results support the conjecture that periodic oscillations in tRNA levels and other factors related to the translation process can induce periodic oscillations in protein levels, and may suggest a new approach for re-engineering genetic

  2. Mattagami River Lake sturgeon entrainment : Little Long generating station facilities

    International Nuclear Information System (INIS)

    Seyler, J.; Evers, J.; McKinley, S.; Evans, R.R.; Prevost, G.; Carson, R.; Phoenix, D.

    1996-01-01

    This project and publication is the result of a collaborative effort by other Large River Ecosystem Unit of Northeast Science (NEST), Ontario Hydro in Kapuskasing, and the New Post First Nation in Cochrane, Ontario, designed to investigate potential solutions to minimize or eliminate the problem of trapped lake sturgeon in the Adam Creek Diversion. The Adam Creek Dam is used to divert excess water from the Mattagami River hydroelectric complex which consists of the Little Long, Smoky Falls, Harmon and Kipling generating stations. The lake sturgeon entrainment problem in the area was discovered in 1990. Potential solutions to the problem include the redirection of flows to mainstream, the placement of a rope barrier, electrical deterrents, physical/electrical guidance systems, sound deterrents, gate modifications, and the continued relocation of fish. The advantages and disadvantages of each of these potential solutions are discussed. Results of the analysis indicated that perceptual and physical barriers have the greatest potential to minimize lake sturgeon entrainment in Adam Creek. 25 refs., 2 tabs., 3 figs., 6 appendices

  3. Characteristics of pressure gradients in downflow condensing of nitrogen in plain, brazed aluminium, plate-fin heat exchanger passages

    International Nuclear Information System (INIS)

    Robertson, J.M.; Blundell, N.; Clarke, R.H.

    1987-01-01

    Measurements of the total two-phase gradients have been made during the downflow condensing of nitrogen in a vertical plain, plate-fin test-section. The results show that pressure recovery occurs only at very low qualities, at low mass flux the falling film is smooth and at high mass flux it is rough. A relationship between the apparent film roughness and the calculated film thickness has been established. The implications for designers of heat exchangers are discussed

  4. AW-101 entrained solids - Solubility versus temperature

    International Nuclear Information System (INIS)

    GJ Lumetta; RC Lettau; GF Piepel

    2000-01-01

    This report describes the results of a test conducted by Battelle to assess the solubility of the solids entrained in the diluted AW-101 low-activity waste (LAW) sample. BNFL requested Battelle to dilute the AW-1-1 sample using de-ionized water to mimic expected plant operating conditions. BNFL further requested Battelle to assess the solubility of the solids present in the diluted AW-101 sample versus temperature conditions of 30, 40, and 50 C. BNFL requested these tests to assess the composition of the LAW supernatant and solids versus expected plant-operating conditions. The work was conducted according to test plan BNFL-TP-29953-7, Rev. 0, Determination of the Solubility of LAW Entrained Solids. The test went according to plan, with no deviations from the test plan

  5. Exploring Entrainment Patterns of Human Emotion in Social Media

    Science.gov (United States)

    Luo, Chuan; Zhang, Zhu

    2016-01-01

    Emotion entrainment, which is generally defined as the synchronous convergence of human emotions, performs many important social functions. However, what the specific mechanisms of emotion entrainment are beyond in-person interactions, and how human emotions evolve under different entrainment patterns in large-scale social communities, are still unknown. In this paper, we aim to examine the massive emotion entrainment patterns and understand the underlying mechanisms in the context of social media. As modeling emotion dynamics on a large scale is often challenging, we elaborate a pragmatic framework to characterize and quantify the entrainment phenomenon. By applying this framework on the datasets from two large-scale social media platforms, we find that the emotions of online users entrain through social networks. We further uncover that online users often form their relations via dual entrainment, while maintain it through single entrainment. Remarkably, the emotions of online users are more convergent in nonreciprocal entrainment. Building on these findings, we develop an entrainment augmented model for emotion prediction. Experimental results suggest that entrainment patterns inform emotion proximity in dyads, and encoding their associations promotes emotion prediction. This work can further help us to understand the underlying dynamic process of large-scale online interactions and make more reasonable decisions regarding emergency situations, epidemic diseases, and political campaigns in cyberspace. PMID:26953692

  6. Alignment strategies for the entrainment of music and movement rhythms.

    Science.gov (United States)

    Moens, Bart; Leman, Marc

    2015-03-01

    Theories of entrainment assume that spontaneous entrainment emerges from dynamic laws that operate via mediators on interactions, whereby entrainment is facilitated if certain conditions are fulfilled. In this study, we show that mediators can be built that affect the entrainment of human locomotion to music. More specifically, we built D-Jogger, a music player that functions as a mediator between music and locomotion rhythms. The D-Jogger makes it possible to manipulate the timing differences between salient moments of the rhythms (beats and footfalls) through the manipulation of the musical period and phase, which affect the condition in which entrainment functions. We conducted several experiments to explore different strategies for manipulating the entrainment of locomotion and music. The results of these experiments showed that spontaneous entrainment can be manipulated, thereby suggesting different strategies on how to embark. The findings furthermore suggest a distinction among different modalities of entrainment: finding the beat (the most difficult part of entrainment), keeping the beat (easier, as a temporal scheme has been established), and being in phase (no entrainment is needed because the music is always adapted to the human rhythm). This study points to a new avenue of research on entrainment and opens new perspectives for the neuroscience of music. © 2014 New York Academy of Sciences.

  7. Exploring Entrainment Patterns of Human Emotion in Social Media.

    Science.gov (United States)

    He, Saike; Zheng, Xiaolong; Zeng, Daniel; Luo, Chuan; Zhang, Zhu

    2016-01-01

    Emotion entrainment, which is generally defined as the synchronous convergence of human emotions, performs many important social functions. However, what the specific mechanisms of emotion entrainment are beyond in-person interactions, and how human emotions evolve under different entrainment patterns in large-scale social communities, are still unknown. In this paper, we aim to examine the massive emotion entrainment patterns and understand the underlying mechanisms in the context of social media. As modeling emotion dynamics on a large scale is often challenging, we elaborate a pragmatic framework to characterize and quantify the entrainment phenomenon. By applying this framework on the datasets from two large-scale social media platforms, we find that the emotions of online users entrain through social networks. We further uncover that online users often form their relations via dual entrainment, while maintain it through single entrainment. Remarkably, the emotions of online users are more convergent in nonreciprocal entrainment. Building on these findings, we develop an entrainment augmented model for emotion prediction. Experimental results suggest that entrainment patterns inform emotion proximity in dyads, and encoding their associations promotes emotion prediction. This work can further help us to understand the underlying dynamic process of large-scale online interactions and make more reasonable decisions regarding emergency situations, epidemic diseases, and political campaigns in cyberspace.

  8. Exploring Entrainment Patterns of Human Emotion in Social Media.

    Directory of Open Access Journals (Sweden)

    Saike He

    Full Text Available Emotion entrainment, which is generally defined as the synchronous convergence of human emotions, performs many important social functions. However, what the specific mechanisms of emotion entrainment are beyond in-person interactions, and how human emotions evolve under different entrainment patterns in large-scale social communities, are still unknown. In this paper, we aim to examine the massive emotion entrainment patterns and understand the underlying mechanisms in the context of social media. As modeling emotion dynamics on a large scale is often challenging, we elaborate a pragmatic framework to characterize and quantify the entrainment phenomenon. By applying this framework on the datasets from two large-scale social media platforms, we find that the emotions of online users entrain through social networks. We further uncover that online users often form their relations via dual entrainment, while maintain it through single entrainment. Remarkably, the emotions of online users are more convergent in nonreciprocal entrainment. Building on these findings, we develop an entrainment augmented model for emotion prediction. Experimental results suggest that entrainment patterns inform emotion proximity in dyads, and encoding their associations promotes emotion prediction. This work can further help us to understand the underlying dynamic process of large-scale online interactions and make more reasonable decisions regarding emergency situations, epidemic diseases, and political campaigns in cyberspace.

  9. Tuning Neural Phase Entrainment to Speech.

    Science.gov (United States)

    Falk, Simone; Lanzilotti, Cosima; Schön, Daniele

    2017-08-01

    Musical rhythm positively impacts on subsequent speech processing. However, the neural mechanisms underlying this phenomenon are so far unclear. We investigated whether carryover effects from a preceding musical cue to a speech stimulus result from a continuation of neural phase entrainment to periodicities that are present in both music and speech. Participants listened and memorized French metrical sentences that contained (quasi-)periodic recurrences of accents and syllables. Speech stimuli were preceded by a rhythmically regular or irregular musical cue. Our results show that the presence of a regular cue modulates neural response as estimated by EEG power spectral density, intertrial coherence, and source analyses at critical frequencies during speech processing compared with the irregular condition. Importantly, intertrial coherences for regular cues were indicative of the participants' success in memorizing the subsequent speech stimuli. These findings underscore the highly adaptive nature of neural phase entrainment across fundamentally different auditory stimuli. They also support current models of neural phase entrainment as a tool of predictive timing and attentional selection across cognitive domains.

  10. Stochastic study on entrainment of floating particles with intake of cooling water of a power plant

    International Nuclear Information System (INIS)

    Kadoyu, Masatake; Wada, Akira

    1979-01-01

    The mortality of ichthyoplanktons, contained in the sea water passing through the cooling water systems of a power plant, may be associated with rising temperature and mechanical effect. In this study, the range and the rate of entrainment of the organisms like ichthyoplanktons floating in the sea caused by the intake of cooling water were stochastically investigated by simulating the average current as well as the flow caused by the intake of water and by taking into consideration random velocity fluctuation without these flows, using a mathematical model. An intake was set along the straight coastline in semi-infinite sea, and the rate of inflow of particles into the intake was simulated by a mathematical model. In the numerical simulation, the average flow as coastal current component and the flow caused by the intake of water were obtained with the hydrodynamic equations of motion and continuity, and the rate of entrainment of floating particles was examined by giving turbulence to the particles in the sea and by calculating the position of each particle every moment. The results are as follows; 1) The range of entrainment of floating particles by the intake of cooling water and its probability were obtained in consideration of the flow rate of cooling water, coast current velocity and diffusion coefficient as parameters. 2) The extent of inflow of floating particles considerably varied with tidal amplitude, diffusion coefficient and the flow rate of cooling water in the sea where the coastal flow has clear periodicity. 3) The extent of entrainment was considerably influenced by the steady current velocity, the velocity distribution in offshore direction and the intake volume in the sea where periodicity is not observed. (Nakai, Y.)

  11. Entrainment and mixing in lock-exchange gravity currents using simultaneous velocity-density measurements

    Science.gov (United States)

    Balasubramanian, Sridhar; Zhong, Qiang

    2018-05-01

    Gravity currents modify their flow characteristics by entraining ambient fluid, which depends on a variety of governing parameters such as the initial density, Δρ, the total initial height of the fluid, H, and the slope of the terrain, α, from where it is released. It is imperative to study the entrainment dynamics of a gravity current in order to have a clear understanding of mixing transitions that govern the flow physics, the velocity mixing layer thickness, δu, and the density mixing layer thickness, δρ. Experiments were conducted in a lock-exchange facility in which the dense fluid was separated from the ambient lighter fluid using a gate. As the gate is released instantaneously, an energy conserving gravity current is formed, for which the only governing parameter is the Reynolds number defined as R e =U/h ν , where U is the front velocity of the gravity current and h is the height of the current. In our study, the bulk Richardson number (inverse of Froude number, Fr), Rib = g/'H Ub2 = 1, takes a constant value for all the experiments, with Ub being the bulk velocity of the current defined as Ub = √{g'H }. Simultaneous particle image velocimetry and planar laser induced fluorescence measurement techniques are employed to get the velocity and density statistics. Using the buoyancy conservation equation, a new flux-based method was formulated for calculating the entrainment coefficient, EF, near the front and head of the propagating gravity current for a Reynolds number range of Re ≈ 485-12 270 used in our experiments. At the head of the current, the results show a mixing transition at Re ≈ 2700 that is attributed to the flow transitioning from weak Holmboe waves to Kelvin-Helmholtz instabilities, in the form of Kelvin-Helmholtz vortex rolls. Following this mixing transition, the entrainment coefficient continued to increase with increasing Reynolds number owing to the occurrence of three-dimensional Kelvin-Helmholtz billows that promote further

  12. Bed-material entrainment potential, Roaring Fork River at Basalt, Colorado

    Science.gov (United States)

    Elliott, John G.

    2002-01-01

    The Roaring Fork River at Basalt, Colorado, has a frequently mobile streambed composed of gravel, cobbles, and boulders. Recent urban and highway development on the flood plain, earlier attempts to realign and confine the channel, and flow obstructions such as bridge openings and piers have altered the hydrology, hydraulics, sediment transport, and sediment deposition areas of the Roaring Fork. Entrainment and deposition of coarse sediment on the streambed and in large alluvial bars have reduced the flood-conveying capacity of the river. Previous engineering studies have identified flood-prone areas and hazards related to inundation and high streamflow velocity, but those studies have not evaluated the potential response of the channel to discharges that entrain the coarse streambed. This study builds upon the results of earlier flood studies and identifies some potential areas of concern associated with bed-material entrainment. Cross-section surveys and simulated water-surface elevations from a previously run HEC?RAS model were used to calculate the boundary shear stress on the mean streambed, in the thalweg, and on the tops of adjacent alluvial bars for four reference streamflows. Sediment-size characteristics were determined for surficial material on the streambed, on large alluvial bars, and on a streambank. The median particle size (d50) for the streambed samples was 165 millimeters and for the alluvial bars and bank samples was 107 millimeters. Shear stresses generated by the 10-, 50-, and 100-year floods, and by a more common flow that just inundated most of the alluvial bars in the study reach were calculated at 14 of the cross sections used in the Roaring Fork River HEC?RAS model. The Shields equation was used with a Shields parameter of 0.030 to estimate the critical shear stress for entrainment of the median sediment particle size on the mean streambed, in the thalweg, and on adjacent alluvial bar surfaces at the 14 cross sections. Sediment-entrainment

  13. Optimizing the Entrainment Geometry of a Dry Powder Inhaler: Methodology and Preliminary Results.

    Science.gov (United States)

    Kopsch, Thomas; Murnane, Darragh; Symons, Digby

    2016-11-01

    For passive dry powder inhalers (DPIs) entrainment and emission of the aerosolized drug dose depends strongly on device geometry and the patient's inhalation manoeuvre. We propose a computational method for optimizing the entrainment part of a DPI. The approach assumes that the pulmonary delivery location of aerosol can be determined by the timing of dose emission into the tidal airstream. An optimization algorithm was used to iteratively perform computational fluid dynamic (CFD) simulations of the drug emission of a DPI. The algorithm seeks to improve performance by changing the device geometry. Objectives were to achieve drug emission that was: A) independent of inhalation manoeuvre; B) similar to a target profile. The simulations used complete inhalation flow-rate profiles generated dependent on the device resistance. The CFD solver was OpenFOAM with drug/air flow simulated by the Eulerian-Eulerian method. To demonstrate the method, a 2D geometry was optimized for inhalation independence (comparing two breath profiles) and an early-bolus delivery. Entrainment was both shear-driven and gas-assisted. Optimization for a delay in the bolus delivery was not possible with the chosen geometry. Computational optimization of a DPI geometry for most similar drug delivery has been accomplished for an example entrainment geometry.

  14. Generation of entrained droplets from an imitated disturbance wave and their deposition on the wall

    International Nuclear Information System (INIS)

    Fukano, T.; Inatomi, T.; Matsuzawa, Y.; Yoshida, T.; Uchimichi, N.

    2003-01-01

    In the present experiment, an isokinetic sampling probe technique was used for the measurement of the local droplet flow rate generated from an imitated disturbance wave, which was constructed by injecting liquid through a slit mounted on the bottom wall of a horizontal rectangular duct. The experimental data on the distribution of entrained droplets and their deposition on the duct wall are presented. As a result, it is clarified that the droplet generation is periodic and the distribution of the droplet flow rate is not uniform in both axial and height directions. And accordingly the droplet flow is fundamentally unsteady. Furthermore, the correlation of the entrainment fraction proposed by Paleev-Filippovich is superior to that by others. (orig.)

  15. Effects of disintegration on anaerobic degradation of sewage excess sludge in downflow stationary fixed film digesters.

    Science.gov (United States)

    Engelhart, M; Krüger, M; Kopp, J; Dichtl, N

    2000-01-01

    The effects of mechanical disintegration on anaerobic digestibility of sewage excess sludge in downflow stationary fixed film (DSFF) digesters were investigated on laboratory scale. Mechanical pretreatment using a high pressure homogenizer led to significantly enhanced concentrations of soluble proteins and carbohydrates in the feed sludge. Using DSFF digesters with two different tubular plastic media as support material it was shown that a stable digestion process could be achieved at hydraulic retention times (HRT) down to 5 days. Compared to conventional digesters at 10 d and 15 d HRT respectively, the degradation of volatile solids was enhanced up to 25%, also resulting in a higher specific biogas production. Further investigations on degradation of soluble proteins and carbohydrates showed that a slowly degradable fraction of carbohydrates was released via disintegration. Using the distribution of chain length and the concentrations of volatile fatty acids as process parameters, the dependability on the HRT and the degree of disintegration (the release of soluble COD) predominated the effects of specific surface area of the support media.

  16. A novel approach for toluene gas treatment using a downflow hanging sponge reactor.

    Science.gov (United States)

    Yamaguchi, Tsuyoshi; Nakamura, Syoichiro; Hatamoto, Masashi; Tamura, Eisuke; Tanikawa, Daisuke; Kawakami, Shuji; Nakamura, Akinobu; Kato, Kaoru; Nagano, Akihiro; Yamaguchi, Takashi

    2018-05-01

    A novel gas-scrubbing bioreactor based on a downflow hanging sponge (DHS) reactor was developed as a new volatile organic compound (VOC) treatment system. In this study, the effects of varying the space velocity and gas/liquid ratio were investigated to assess the effectiveness of using toluene gas as a model VOC. Under optimal conditions, the toluene removal rate was greater than 80%, and the maximum elimination capacity was observed at approximately 13 g-C m -3  h -1 . The DHS reactor demonstrated slight pressure loss (20 Pa) and a high concentration of suspended solids (up to 30,000 mg/L-sponge). Cloning analysis of the 16S rRNA and functional genes of toluene degradation pathways (tmoA, todC, tbmD, xylA, and bssA) revealed that the clones belonging to the toluene-degrading bacterium Pseudomonas putida constituted the predominant species detected at the bottom of the DHS reactor. The toluene-degrading bacteria Pseudoxanthomonas spadix and Pseudomonas sp. were also detected by tmoA- and todC-targeted cloning analyses, respectively. These results demonstrate the potential for the industrial application of this novel DHS reactor for toluene gas treatment.

  17. The Role of Oscillatory Phase in Determining the Temporal Organization of Perception: Evidence from Sensory Entrainment.

    Science.gov (United States)

    Ronconi, Luca; Melcher, David

    2017-11-01

    Recent behavioral, neuroimaging, and neurophysiological studies have renewed the idea that the information processing within different temporal windows is linked to the phase and/or frequency of the ongoing oscillations, predominantly in the theta/alpha band (∼4-7 and 8-12 Hz, respectively). However, being correlational in nature, this evidence might reflect a nonfunctional byproduct rather than having a causal role. A more direct link can be shown with methods that manipulate oscillatory activity. Here, we used audiovisual entrainment at different frequencies in the prestimulus period of a temporal integration/segregation task. We hypothesized that entrainment would align ongoing oscillations and drive them toward the stimulation frequency. To reveal behavioral oscillations in temporal perception after the entrainment, we sampled the segregation/integration performance densely in time. In Experiment 1, two groups of human participants (both males and females) received stimulation either at the lower or the upper boundary of the alpha band (∼8.5 vs 11.5 Hz). For both entrainment frequencies, we found a phase alignment of the perceptual oscillation across subjects, but with two different power spectra that peaked near the entrainment frequency. These results were confirmed when perceptual oscillations were characterized in the time domain with sinusoidal fittings. In Experiment 2, we replicated the findings in a within-subject design, extending the results for frequencies in the theta (∼6.5 Hz), but not in the beta (∼15 Hz), range. Overall, these findings show that temporal segregation can be modified by sensory entrainment, providing evidence for a critical role of ongoing oscillations in the temporal organization of perception. SIGNIFICANCE STATEMENT The continuous flow of sensory input is not processed in an analog fashion, but rather is grouped by the perceptual system over time. Recent studies pinpointed the phase and/or frequency of the neural

  18. Leak detection on the DIII-D tokamak using helium entrainment techniques

    International Nuclear Information System (INIS)

    Brooks, N.H.; Baxi, C.; Anderson, P.

    1988-01-01

    The entrainment of helium in a viscous gas flow was utilized to compartmentalize, and then to pinpoint, a leak across the inner skin of the double-walled DIII-D vacuum vessel. Inaccessible from the outside, the leak connected the cooling channels in the wall interspace with the primary vacuum chamber. By entraining helium in the pressurized flow from the single-pass gas circulation system, well-defined portions of the wall were exposed to helium without disassembly of the poorly accessible cooling manifolds. Varying the helium injection point permitted the localization of the leak to a single 30 0 toroidal sector of the vessel. The exact location of the leak was found from inside the vessel by spraying helium on suspect regions, while sweeping the contents of the cooling channels to the foreline of a Varian Contraflow leak detector with a 0.1 Pa m 3 /s flow of nitrogen. Flow speed calculations were used to predict the response time to entrained helium of the actual leak detection setup

  19. On-line ultrasonic gas entrainment monitor

    International Nuclear Information System (INIS)

    Day, C.K.; Pedersen, H.N.

    1978-01-01

    Apparatus employing ultrasonic energy for detecting and measuring the quantity of gas bubbles present in liquids being transported through pipes is described. An ultrasonic transducer is positioned along the longitudinal axis of a fluid duct, oriented to transmit acoustic energy radially of the duct around the circumference of the enclosure walls. The back-reflected energy is received centrally of the duct and interpreted as a measure of gas entrainment. One embodiment employs a conical reflector to direct the transmitted acoustic energy radially of the duct and redirect the reflected energy back to the transducer for reception. A modified embodiment employs a cylindrical ultrasonic transducer for this purpose

  20. Assessment of impact due to entrainment of ichthyoplankton

    International Nuclear Information System (INIS)

    Horst, T.J.

    1975-01-01

    Three approaches to the assessment of impact associated with the entrainment of ichthyoplankton into power stations are discussed. The first is the estimation of the probability of mortality for those organisms entrained. The second is the assessment to the fish populations which have the egg and larvae life stages entrained. The third approach is the assessment of impact to the community or ecosystem. Some models are presented as examples for each of the three approaches. (U.S.)

  1. Simple estimate of entrainment rate of pollutants from a coastal discharge into the surf zone.

    Science.gov (United States)

    Wong, Simon H C; Monismith, Stephen G; Boehm, Alexandria B

    2013-10-15

    Microbial pollutants from coastal discharges can increase illness risks for swimmers and cause beach advisories. There is presently no predictive model for estimating the entrainment of pollution from coastal discharges into the surf zone. We present a novel, quantitative framework for estimating surf zone entrainment of pollution at a wave-dominant open beach. Using physical arguments, we identify a dimensionless parameter equal to the quotient of the surf zone width l(sz) and the cross-flow length scale of the discharge la = M(j) (1/2)/U(sz), where M(j) is the discharge's momentum flux and U(sz) is a representative alongshore velocity in the surf zone. We conducted numerical modeling of a nonbuoyant discharge at an alongshore uniform beach with constant slope using a wave-resolving hydrodynamic model. Using results from 144 numerical experiments we develop an empirical relationship between the surf zone entrainment rate α and l(sz)/(la). The empirical relationship can reasonably explain seven measurements of surf zone entrainment at three diverse coastal discharges. This predictive relationship can be a useful tool in coastal water quality management and can be used to develop predictive beach water quality models.

  2. Formation and entrainment of fluid mud layers in troughs of subtidal dunes in an estuarine turbidity zone

    DEFF Research Database (Denmark)

    Becker, Marius; Schrottke, Kerstin; Bartholomä, Alexander

    2013-01-01

    25 g/L below the lutocline to 70 g/L at the river bed, whereas the gelling concentration was below 70 g/L. Sites of fluid mud formation coincided with the location of the estuarine turbidity zone during slack water. On average, near-bed density gradients were initially observed in dune troughs 1.2 h...... before slack water, and all fluid mud layers were entrained 2.3 h after slack water. No shear instabilities occurred until 1.8 h after slack water. While the flow was oriented in the dune direction, rapid entrainment was related to the development of the turbulent flow field behind dunes and is explained...... to be induced by advection of strong turbulence during accelerating currents. Fluid mud layers in dune troughs were entrained at an earlier point in time after slack water, compared to adjacent layers formed on a comparatively flat bed, where dune crests did not protrude from the lutocline....

  3. A hybrid model to predict the onset of gas entrainment with surface tension effects

    International Nuclear Information System (INIS)

    Saleh, W.; Bowden, R.C.; Hassan, I.G.; Kadem, L.

    2008-01-01

    The onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink. Through use of the Kelvin-Laplace equation the model included the effects of surface tension. The resulting model required further knowledge of the flow field, specifically the dip radius of curvature prior to the onset of gas entrainment. The dip shape and size was investigated experimentally and correlations were provided to characterize the dip in terms of the discharge Froude number. The experimental correlation was used in conjunction with the theoretical model to predict the critical height. The results showed that by including surface tension effects the predicted critical height showed excellent agreement with experimental data. Surface tension reduces the critical height through the Bond number

  4. Aerosol entrainment from a sparged non-Newtonian slurry.

    Science.gov (United States)

    Fritz, Brad G

    2006-08-01

    Previous bench-scale experiments have provided data necessary for the development of empirical models that describe aerosol entrainment from bubble bursting. However, previous work has not been extended to non-Newtonian liquid slurries. Design of a waste treatment plant on the Hanford Site in Washington required an evaluation of the applicability of these models outside of their intended range. For this evaluation, aerosol measurements were conducted above an air-sparged mixing tank filled with simulated waste slurry possessing Bingham plastic rheological properties. Three aerosol-size fractions were measured at three sampling heights and for three different sparging rates. The measured entrainment was compared with entrainment models. One model developed based on bench-scale air-water experiments agreed well with measured entrainment. Another model did not agree well with the measured entrainment. It appeared that the source of discrepancy between measured and modeled entrainment stemmed from application beyond the range of data used to develop the model. A possible separation in entrainment coefficients between air-water and steam-water systems was identified. A third entrainment model was adapted to match experimental conditions and fit a posteri to the experimental data, resulting in a modified version that resulted in estimated entrainment rates similar to the first model.

  5. Development of a custom-made "smart-sphere" to assess incipient entrainment by rolling

    Science.gov (United States)

    Valyrakis, Manousos; Kitsikoudis, Vasileios; Alexakis, Athanasios; Trinder, Jon

    2017-04-01

    The most widely applied criterion for sediment incipient motion in engineering applications is the time- and space-averaged approach of critical Shields shear stress. Nonetheless, in the recent years published research has highlighted the importance of turbulence fluctuations in sediment incipient motion and its stochastic character. The present experimental study investigates statistically the link of the response of a "smart-pebble" to hydrodynamics in near-critical flow conditions and discusses how such a device can be utilized in engineering design. A set of specifically designed fluvial experiments monitoring the entrainment conditions for a "smart-pebble", were carried out in a tilting, recirculating flume in turbulent flow conditions while three-dimensional flow measurements were obtained with an acoustic Doppler velocimeter. The "smart-pebble" employed herein is a custom-made instrumented sphere with 7 cm diameter, which has a number of sensors embedded within its waterproof 3D-printed plastic shell. Specifically, the "smart-pebble" is equipped with miniaturized, off the shelf, low-cost, three-dimensional acceleration, orientation and angular displacement sensors. A 3D-printed local micro topography of known geometry was installed in the flume's test section and the "smart-pebble" was placed there in order to facilitate the analysis. Every time the "smart-sphere" is displaced by the flow a downstream located pin blocks its full entrainment. This allows for continuous recording of the entrainment events due to the passage of energetic events, after which the "smart-pebble" returns to its resting pocket. The "smart-pebble" device under such a configuration allows the recording of normally indiscernible (with the naked eye) vibrations, twitching motions, and full entrainments for the studied particle, allowing its analysis from a Langrangian framework. During the incipient motion experiments the retrieved data are stored in an internal memory unit or

  6. Visuomotor Entrainment and the Frequency-Dependent Response of Walking Balance to Perturbations.

    Science.gov (United States)

    Franz, Jason R; Francis, Carrie; Allen, Matt; Thelen, Darryl G

    2016-08-26

    Visuomotor entrainment, or the synchronization of motor responses to visual stimuli, is a naturally emergent phenomenon in human standing. Our purpose was to investigate the prevalence and resolution of visuomotor entrainment in walking and the frequency-dependent response of walking balance to perturbations. We used a virtual reality environment to manipulate optical flow in ten healthy young adults during treadmill walking. A motion capture system recorded trunk, sacrum, and heel marker trajectories during a series of 3-min conditions in which we perturbed a virtual hallway mediolaterally with systematic changes in the driving frequencies of perceived motion. We quantified visuomotor entrainment using spectral analyses and balance deficits using trunk sway, gait variability, and detrended fluctuation analyses (DFA). ML kinematics were highly sensitive to visual perturbations, and instinctively synchronized (i.e., entrained) to a broad range of driving frequencies of perceived ML motion. However, the influence of visual perturbations on metrics of walking balance was frequency-dependent and governed by their proximity to stride frequency. Specifically, we found that a driving frequency nearest to subjects' average stride frequency uniquely compromised trunk sway, gait variability, and step-to-step correlations. We conclude that visuomotor entrainment is a robust and naturally emerging phenomenon during human walking, involving coordinated and frequency-dependent adjustments in trunk sway and foot placement to maintain balance at the whole-body level. These findings provide mechanistic insight into how the visuomotor control of walking balance is disrupted by visual perturbations and important reference values for the emergence of balance deficits due to age, injury, or disease.

  7. Drop size measurements and entrainment in APR1400 during LBLOCA reflood phase

    International Nuclear Information System (INIS)

    Lee, Eo Hwak

    2010-02-01

    A study has been performed to investigate droplet size in the nuclear reactor of APR1400 during LBLOCA reflood phase and to develop droplet entrainment and deposition models for SPACE (Safety and Performance CodE) which is a safety analysis tool for PWR being developed in Korea. A freezing technique for measuring the size of droplets was developed to obtain the droplet size distribution in horizontal annular flow in a pipe with a 37.1 mm diameter. Droplets are frozen by using an extremely low temperature nitrogen gas with liquid film extraction. They are then photographed with a microscope and a CCD camera and measured by means of an image process. The results are compared with various experimental data. The droplet sizes measured by the freezing technique are comparable with those measured by other methods at a high superficial air velocity (of 50 m/s). However, because of the film extraction problem, the droplet sizes measured at a low superficial air velocity of less than 40 m/s are higher than those measured by other methods. A present method suggested for predicting the Sauter mean diameter is based on the maximum droplet size correlation for the experimental data, with and without liquid film extraction. The average droplet size is remarkably smaller downstream of the liquid film extractor because large droplets from the liquid film are excluded. In order to understand and to predict a heat transfer between superheated steam and droplets properly during reflood phase of LBLOCA, it is very important to measure broken droplet sizes by spacer grids. A study, therefore, has been performed to investigate droplet size in rod bundles with spacer grids and to develop a spacer grid droplet breakup model for safety analysis codes. Experiments were conducted with liquid droplets (SMD of 300∼700 μm) and various spacer grids at superficial air velocity of 10 m/s and 20 m/s based on FLECHT SEASET. The test channel and the grids were heated to 150 .deg. C to prevent

  8. Drop size measurements and entrainment in APR1400 during LBLOCA reflood phase

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eo Hwak

    2010-02-15

    A study has been performed to investigate droplet size in the nuclear reactor of APR1400 during LBLOCA reflood phase and to develop droplet entrainment and deposition models for SPACE (Safety and Performance CodE) which is a safety analysis tool for PWR being developed in Korea. A freezing technique for measuring the size of droplets was developed to obtain the droplet size distribution in horizontal annular flow in a pipe with a 37.1 mm diameter. Droplets are frozen by using an extremely low temperature nitrogen gas with liquid film extraction. They are then photographed with a microscope and a CCD camera and measured by means of an image process. The results are compared with various experimental data. The droplet sizes measured by the freezing technique are comparable with those measured by other methods at a high superficial air velocity (of 50 m/s). However, because of the film extraction problem, the droplet sizes measured at a low superficial air velocity of less than 40 m/s are higher than those measured by other methods. A present method suggested for predicting the Sauter mean diameter is based on the maximum droplet size correlation for the experimental data, with and without liquid film extraction. The average droplet size is remarkably smaller downstream of the liquid film extractor because large droplets from the liquid film are excluded. In order to understand and to predict a heat transfer between superheated steam and droplets properly during reflood phase of LBLOCA, it is very important to measure broken droplet sizes by spacer grids. A study, therefore, has been performed to investigate droplet size in rod bundles with spacer grids and to develop a spacer grid droplet breakup model for safety analysis codes. Experiments were conducted with liquid droplets (SMD of 300∼700 μm) and various spacer grids at superficial air velocity of 10 m/s and 20 m/s based on FLECHT SEASET. The test channel and the grids were heated to 150 .deg. C to prevent

  9. Liquid entrainment through orifices by sparging gas

    International Nuclear Information System (INIS)

    Bonnet, J.M.; Malara, M.; Amblard, M.; Seiler, J.M.

    2001-01-01

    Corium Coolability by water flood during an MCCI (Molten Corium Concrete Interaction) is still an open problem. Several physical mechanisms have been identified which may reduce significantly and finally stop the ablation of concrete. Among these mechanisms, corium ejection by sparging gas into the overlying water may represent an important contribution. This mechanism was at the origin of a large and coolable debris bed and volcano formation in the MACE M3B test. This mechanism has also been observed in simulant material tests performed at UCSB and at FZK. The objective of the work, which is described in the present paper, is to model this mechanism and to quantify the liquid entrainment rate by sparging gas. (author)

  10. Projected entrainment of fish resulting from aggregate dredging

    International Nuclear Information System (INIS)

    Drabble, Ray

    2012-01-01

    Previous research to assess impacts from aggregate dredging has focussed on infaunal species with few studies made of fish entrainment. Entrainment evidence from hydraulic dredging studies is reviewed to develop a sensitivity index for benthic fish. Environmental monitoring attendant with the granting of new licences in the Eastern Channel Region (ECR) in 2006 offers a unique opportunity to assess the effects of dredging upon fish. Projected theoretical fish entrainment rates are calculated based upon: abundance data from 4m beam trawl sampling of fish species over the period 2005–2008; sensitivity data; and dredging activity and footprint derived from Electronic monitoring System (EMS) data. Results have been compared with actual entrainment rates and also against summary results from independent analysis of the changes in fish population over the period 2005–2008 (). The case is made for entrainment surveys to form part of impact monitoring for marine aggregate dredging.

  11. The dynamics of a channel-fed lava flow on Pico Partido volcano, Lanzarote

    Science.gov (United States)

    Woodcock, Duncan; Harris, Andrew

    2006-09-01

    A short length of channel on Pico Partido volcano, Lanzarote, provides us the opportunity to examine the dynamics of lava flowing in a channel that extends over a sudden break in slope. The 1 2-m-wide, 0.5 2-m-deep channel was built during the 1730 1736 eruptions on Lanzarote and exhibits a sinuous, well-formed channel over a steep (11° slope) 100-m-long proximal section. Over-flow units comprising smooth pahoehoe sheet flow, as well as evidence on the inner channel walls for multiple (at least 11) flow levels, attest to unsteady flow in the channel. In addition, superelevation is apparent at each of the six bends along the proximal channel section. Superelevation results from banking of the lava as it moves around the bend thus causing preferential construction of the outer bank. As a result, the channel profile at each bend is asymmetric with an outer bank that is higher than the inner bank. Analysis of superelevation indicates flow velocities of ~8 m s 1. Our analysis of the superelevation features is based on an inertia-gravity balance, which we show is appropriate, even though the down-channel flow is in laminar flow. We use a viscosity-gravity balance model, together with the velocities calculated from superelevation, to obtain viscosities in the range 25 60 Pa s (assuming that the lava behaved as a Newtonian liquid). Estimated volume fluxes are in the range 7 12 m3 s 1. An apparent down-flow increase in derived volume flux may have resulted from variable supply or bulking up of the flow due to vesiculation. Where the channel moves over a sharp break in slope and onto slopes of ~6°, the channel becomes less well defined and widens considerably. At the break of slope, an elongate ridge extends across the channel. We speculate that this ridge was formed as a result of a reduction in velocity immediately below the break of slope to allow deposition of entrained material or accretion of lava to the channel bed as a result of a change in flow regime or depth.

  12. Turbine flow meter response in two-phase flows

    International Nuclear Information System (INIS)

    Shim, W.J.; Dougherty, T.J.; Cheh, H.Y.

    1996-01-01

    The purpose of this paper is to suggest a simple method of calibrating turbine flow meters to measure the flow rates of each phase in a two-phase flow. The response of two 50.8 mm (2 inch) turbine flow meters to air-water, two-phase mixtures flowing vertically in a 57 mm I.D. (2.25 inch) polycarbonate tube has been investigated for both upflow and downflow. The flow meters were connected in series with an intervening valve to provide an adjustable pressure difference between them. Void fractions were measured by two gamma densitometers, one upstream of the flow meters and the other downstream. The output signal of the turbine flow meters was found to depend only on the actual volumetric flow rate of the gas, F G , and liquid, F L , at the location of the flow meter

  13. MAGNETOHYDRODYNAMICS STUDY OF THREE-DIMENSIONAL FAST MAGNETIC RECONNECTION FOR INTERMITTENT SNAKE-LIKE DOWNFLOWS IN SOLAR FLARES

    International Nuclear Information System (INIS)

    Shimizu, T.; Kondo, K.; Ugai, M.; Shibata, K.

    2009-01-01

    Three-dimensional instability of the spontaneous fast magnetic reconnection is studied with magnetohydrodynamics (MHD) simulation, where the two-dimensional model of the spontaneous fast magnetic reconnection is destabilized in three dimensions. In two-dimensional models, every plasma condition is assumed to be uniform in the sheet current direction. In that case, it is well known that the two-dimensional fast magnetic reconnection can be caused by current-driven anomalous resistivity, when an initial resistive disturbance is locally put in a one-dimensional current sheet. In this paper, it is studied whether the two-dimensional fast magnetic reconnection can be destabilized or not when the initial resistive disturbance is three dimensional, i.e., that which has weak fluctuations in the sheet current direction. According to our study, the two-dimensional fast magnetic reconnection is developed to the three-dimensional intermittent fast magnetic reconnection which is strongly localized in the sheet current direction. The resulting fast magnetic reconnection repeats to randomly eject three-dimensional magnetic loops which are very similar to the intermittent downflows observed in solar flares. In fact, in some observations of solar flares, the current sheet seems to be approximately one dimensional, but the fast magnetic reconnection is strongly localized in the sheet current direction, i.e., fully three dimensional. In addition, the observed plasma downflows as snake-like curves. It is shown that those observed features are consistent with our numerical MHD study.

  14. Pretreatment and Feeding of Biomass for Pressurized Entrained Flow Gasification

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Karel; Pohořelý, Michael; Hartman, Miloslav; Martinec, J.

    2009-01-01

    Roč. 90, č. 5 (2009), s. 629-635 ISSN 0378-3820 R&D Projects: GA AV ČR IAA400720701 Grant - others:RFCS(XE) CT/2007/00005 Institutional research plan: CEZ:AV0Z40720504 Keywords : biomass * feeding * gasification Subject RIV: DJ - Water Pollution ; Quality Impact factor: 2.321, year: 2009

  15. Entrained Flow Reactor Study of KCl Capture by Solid Additives

    DEFF Research Database (Denmark)

    Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao

    been proved to be very promising additives and havereceived extensive studies during the past decades. However, mostprevious studies were carried out in fixed-bed reactors where the reaction conditions are obviously different from that in suspension fired boilers.Detailed knowledge on the reaction...

  16. Liquid dispersion in trickle-bed reactors with gas-liquid cocurrent downflow

    International Nuclear Information System (INIS)

    Chu, C.F.; Ng, K.M.

    1986-01-01

    The flow pattern can deviate from ideal plug flow in both trickling and pulsing flows. The liquid dispersion in those flow regimes are investigated separately, as the mechanisms causing the deviation of flow pattern from plug flow are different. In trickling flow, the dispersion of the liquid phase occurs in the flow path which is determined with computer-generated packed column. Dispersion in pulsing flow is studied with a combination of the method of characteristics and analysis of liquid dispersion in the liquid slug and gas pulse. The axial dispersion coefficients are then determined based on Monte Carlo simulation. Finally, liquid dispersion in trickle beds containing porous packings is also discussed

  17. FPIV study of gas entrainment by a hollow cone spray submitted to variable density

    Energy Technology Data Exchange (ETDEWEB)

    Prosperi, B. [UMR CNRS/INPT-UPS 5502, Institut de Mecanique des Fluides de Toulouse, Toulouse (France); P GS AD INCAS, Siemens VDO Automotive, 1, av Paul Ourliac, BP 1149, Toulouse (France); Delay, G.; Bazile, R. [UMR CNRS/INPT-UPS 5502, Institut de Mecanique des Fluides de Toulouse, Toulouse (France); Helie, J.; Nuglish, H.J. [P GS AD INCAS, Siemens VDO Automotive, 1, av Paul Ourliac, BP 1149, Toulouse (France)

    2007-08-15

    The gas entrainment in a hollow cone spray submitted to variable density is studied experimentally in order to better understand the effect on mixture formation. Particle image velocimetry on fluorescent tracers, associated with a specific processing of the instantaneous velocity fields have been applied to obtain measurement in the close vicinity of the spray edge. In the ''quasi-steady'' region of the spray, important effect of the ambient density on the mass flow rate of entrained gas (m{sub e}) have been pointed out. The axial evolution of m{sub e} is in good agreement with an integral model that takes the momentum exchange between phases into account. (orig.)

  18. Topflow-experiments on direct condensation and bubble entrainment. Technical report

    International Nuclear Information System (INIS)

    Seidel, Tobias; Lucas, Dirk; Beyer, Matthias

    2016-01-01

    Direct Contact Condensation between steam and water as well as bubble entrainment below the water surface play an important role in different accident scenarios for light water reactors. One example is the emergency core cooling water injection into a two-phase mixture. It has to be considered for example to evaluate potential pressurized thermal shock phenomena. This report documents experiments conducted in flat basin inside the TOPFLOW pressure chamber aiming on the generation of a database useful for CFD model development and validation. It comprises 3 different setups: condensation at a stratified flow of sub-cooled water, condensation at a sub-cooled water jet and a combination of both phenomena with steam bubble entrainment. The documentation includes all details on the experimental set up, on experimental conditions (experimental matrices), on the conduction of the experiments, on measuring techniques used and on data evaluation procedures. In addition, selected results are presented.

  19. Physical and Numerical Investigations of Mould Flux Entrainment into Liquid Steel

    Directory of Open Access Journals (Sweden)

    Jowsa J.

    2016-12-01

    Full Text Available This paper presents results of model tests, performed in order to analyze phenomenon of slag droplets entrainment into steel in mould, during continuous casting process. The carried out studies took the form of laboratory experiments using physical model, in which – using similarity criteria – the behaviour of interfacial boundary liquid steel-liquid slag has been simulated using water and silicon oils, differing in physicochemical properties. Additionally, based on PIV (Particle Image Velocimetry measurements and numerical simulations, vector flow field and values of critical velocities, at which observed the occurrence of interfacial boundary silicon oil-water instability have been identified. Based on the carried out investigations, results, that illustrate relationship between critical entrainment velocity and physicochemical properties of oils have been presented.

  20. Electrification of particulate entrained fluid flows—Mechanisms, applications, and numerical methodology

    International Nuclear Information System (INIS)

    Wei, Wei; Gu, Zhaolin

    2015-01-01

    Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas–solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The

  1. Electrification of particulate entrained fluid flows—Mechanisms, applications, and numerical methodology

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Wei [School of Energy and Power Engineering, Wuhan University of Technology, Wuhan, Hubei, 430063 (China); School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049 (China); Gu, Zhaolin, E-mail: guzhaoln@mail.xjtu.edu.cn [School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049 (China)

    2015-10-28

    Particulates in natural and industrial flows have two basic forms: liquid (droplet) and solid (particle). Droplets would be charged in the presence of the applied electric field (e.g. electrospray). Similar to the droplet charging, particles can also be charged under the external electric field (e.g. electrostatic precipitator), while in the absence of external electric field, tribo-electrostatic charging is almost unavoidable in gas–solid two-phase flows due to the consecutive particle contacts (e.g. electrostatic in fluidized bed or wind-blown sand). The particle charging may be beneficial, or detrimental. Although electrostatics in particulate entrained fluid flow systems have been so widely used and concerned, the mechanisms of particulate charging are still lack of a thorough understanding. The motivation of this review is to explore a clear understanding of particulate charging and movement of charged particulate in two-phase flows, by summarizing the electrification mechanisms, physical models of particulate charging, and methods of charging/charged particulate entrained fluid flow simulations. Two effective methods can make droplets charged in industrial applications: corona charging and induction charging. The droplet charge to mass ratio by corona charging is more than induction discharge. The particle charging through collisions could be attributed to electron transfer, ion transfer, material transfer, and/or aqueous ion shift on particle surfaces. The charges on charged particulate surface can be measured, nevertheless, the charging process in nature or industry is difficult to monitor. The simulation method might build a bridge of investigating from the charging process to finally charged state on particulate surface in particulate entrained fluid flows. The methodology combining the interface tracking under the action of the applied electric with the fluid flow governing equations is applicable to the study of electrohydrodynamics problems. The

  2. Counter-current flow limited CHF in thin rectangular channels

    International Nuclear Information System (INIS)

    Cheng, L.Y.

    1990-01-01

    An analytical expression for counter-current-flow-limitation (CCFL) was used to predict critical heat flux (CHF) for downward flow in thin vertical rectangular channels which are prototypes of coolant channels in test and research nuclear reactors. Top flooding is the mechanism for counter-current flow limited CHF. The CCFL correlation also was used to determine the circulation and flooding-limited CHF. Good agreements were observed between the period the model predictions and data on the CHF for downflow. The minimum CHF for downflow is lower than the flooding-limited CHF and it is predicted to occur at a liquid flow rate higher than that at the flooding limit. 17 refs., 7 figs

  3. Microphysical imprint of entrainment in warm cumulus

    Directory of Open Access Journals (Sweden)

    Jennifer D. Small

    2013-07-01

    Full Text Available We analyse the cloud microphysical response to entrainment mixing in warm cumulus clouds observed from the CIRPAS Twin Otter during the GoMACCS field campaign near Houston, Texas, in summer 2006. Cloud drop size distributions and cloud liquid water contents from the Artium Flight phase-Doppler interferometer in conjunction with meteorological observations are used to investigate the degree to which inhomogeneous versus homogeneous mixing is preferred as a function of height above cloud base, distance from cloud edge and aerosol concentration. Using four complete days of data with 101 cloud penetrations (minimum 300 m in length, we find that inhomogeneous mixing primarily explains liquid water variability in these clouds. Furthermore, we show that there is a tendency for mixing to be more homogeneous towards the cloud top, which we attribute to the combination of increased turbulent kinetic energy and cloud drop size with altitude which together cause the Damköhler number to increase by a factor of between 10 and 30 from cloud base to cloud top. We also find that cloud edges appear to be air from cloud centres that have been diluted solely through inhomogeneous mixing. Theory predicts the potential for aerosol to affect mixing type via changes in drop size over the range of aerosol concentrations experienced (moderately polluted rural sites to highly polluted urban sites. However, the observations, while consistent with this hypothesis, do not show a statistically significant effect of aerosol on mixing type.

  4. Music and emotions: from enchantment to entrainment.

    Science.gov (United States)

    Vuilleumier, Patrik; Trost, Wiebke

    2015-03-01

    Producing and perceiving music engage a wide range of sensorimotor, cognitive, and emotional processes. Emotions are a central feature of the enjoyment of music, with a large variety of affective states consistently reported by people while listening to music. However, besides joy or sadness, music often elicits feelings of wonder, nostalgia, or tenderness, which do not correspond to emotion categories typically studied in neuroscience and whose neural substrates remain largely unknown. Here we review the similarities and differences in the neural substrates underlying these "complex" music-evoked emotions relative to other more "basic" emotional experiences. We suggest that these emotions emerge through a combination of activation in emotional and motivational brain systems (e.g., including reward pathways) that confer its valence to music, with activation in several other areas outside emotional systems, including motor, attention, or memory-related regions. We then discuss the neural substrates underlying the entrainment of cognitive and motor processes by music and their relation to affective experience. These effects have important implications for the potential therapeutic use of music in neurological or psychiatric diseases, particularly those associated with motor, attention, or affective disturbances. © 2015 New York Academy of Sciences.

  5. The Entrainment Rate for Buoyant Plumes in a Crossflow

    Science.gov (United States)

    Devenish, B. J.; Rooney, G. G.; Webster, H. N.; Thomson, D. J.

    2010-03-01

    We consider large-eddy simulations (LES) of buoyant plumes from a circular source with initial buoyancy flux F 0 released into a stratified environment with constant buoyancy frequency N and a uniform crossflow with velocity U. We make a systematic comparison of the LES results with the mathematical theory of plumes in a crossflow. We pay particular attention to the limits {tilde{U}≪1} and {tilde{U}≫ 1}, where {tilde{U}=U/(F_0 N)^{1/4}}, for which analytical results are possible. For {tilde{U}≫ 1}, the LES results show good agreement with the well-known two-thirds law for the rise in height of the plume. Sufficiently far above the source, the centreline vertical velocity of the LES plumes is consistent with the analytical z -1/3 and z -1/2 scalings for respectively {tilde{U}≪ 1} and {tilde{U}≫ 1}. In the general case, where the entrainment is assumed to be the sum of the contributions from the horizontal and vertical velocity components, we find that the discrepancy between the LES data and numerical solutions of the plume equations is largest for {tilde{U}=O(1)}. We propose a modified additive entrainment assumption in which the contributions from the horizontal and vertical velocity components are not equally weighted. We test this against observations of the plume generated by the Buncefield fire in the U.K. in December 2005 and find that the results compare favourably. We also show that the oscillations of the plume as it settles down to its final rise height may be attenuated by the radiation of gravity waves. For {tilde{U}≪ 1} the oscillations decay rapidly due to the transport of energy away from the plume by gravity waves. For {tilde{U}>rsim 1} the gravity waves travel in the same direction and at the same speed as the flow. In this case, the oscillations of the plume do not decay greatly by radiation of gravity waves.

  6. A comparative efficacy study of photic driving brainwave entrainment technology with a novel form of more direct entrainment

    Science.gov (United States)

    Knowles, Richard Thomas

    This exploratory study compared the efficacy of a novel brainwave electromagnetic (EM) entrainment technology against a more conventional technology utilizing the photic-driving technique. Both experimental conditions were also compared with a 7-minute control session that took place immediately before each stimulation session. The Schumann Resonance (SR) frequency was selected as the delivery signal and was chosen because of previous findings suggesting that entrainment to this frequency can often produce transpersonal if not paranormal, experiences in the entrainee, which sometimes resemble remote viewing or out-of-body experiences. A pilot study determined which of two novel entrainment modalities (a copper coil or a 16-solenoid headset) worked most effectively for use with the rest of the study. In the main study, an artificial SR signal at 7.8Hz was delivered during the photic-driving sessions, but a recording of the real-time SR was used to deliver the entrainment signal during sessions devoted to the electromagnetic entrainment modality. Sixteen participants were recruited from the local area, and EEG recordings were acquired via a 32-channel Deymed electroencephalography system. Comparative analyses were performed between the control and experimental portions of each session to assess for efficacy of the novel entrainment modality used, and, in the main study, between the electromagnetic and photic-driving sessions, to assess for differential entrainment efficacy between these groups. A follow-up study was additionally performed primarily to determine whether responders could replicate their entrainment effect from the main study. Results showed that EM entrainment appeared to be possible but is not nearly as robust or reliable as photic driving. Additionally, no profound transpersonal or paranormal experiences were elicited during the course of the study, and, when asked, participants were not able to determine with any degree of success, when the

  7. Aerosol entrainment from a sparged non-Newtonian slurry

    International Nuclear Information System (INIS)

    Fritz, Brad G.

    2006-01-01

    Aerosol measurements were conducted above a half-scale air sparged mixing tank filled with simulated waste slurry. Three aerosol size fractions were measured at three sampling heights at three different sparging rates using a filter based ambient air sampling technique. Aerosol concentrations in the head space above the closed tank demonstrated a wide range, varying between 97 ?g m-3 for PM2.5 and 5650 ?g m-3 for TSP. The variation in concentrations was a function of sampling heights, size fraction and sparging rate. Measured aerosol entrainment coefficients showed good agreement with existing entrainment models. The models evaluated generally over predicted the entrainment, but were within a factor of two of the measured entrainment. This indicates that the range of applicability of the models may be extendable to include sparged slurries with Bingham plastic rheological properties

  8. Morphodynamic Modeling of the Lower Yellow River, China: Flux (Equilibrium) Form or Entrainment (Nonequilibrium) Form of Sediment Mass Conservation?

    Science.gov (United States)

    An, C.; Parker, G.; Ma, H.; Naito, K.; Moodie, A. J.; Fu, X.

    2017-12-01

    Models of river morphodynamics consist of three elements: (1) a treatment of flow hydraulics, (2) a formulation relating some aspect of sediment transport to flow hydraulics, and (3) a description of sediment conservation. In the case of unidirectional river flow, the Exner equation of sediment conservation is commonly described in terms of a flux-based formulation, in which bed elevation variation is related to the streamwise gradient of sediment transport rate. An alternate formulation of the Exner equation, however, is the entrainment-based formulation in which bed elevation variation is related to the difference between the entrainment rate of bed sediment into suspension and the deposition rate of suspended sediment onto the bed. In the flux-based formulation, sediment transport is regarded to be in a local equilibrium state (i.e., sediment transport rate locally equals sediment transport capacity). However, the entrainment-based formulation does not require this constraint; the sediment transport rate may lag in space and time behind the changing flow conditions. In modeling the fine-grained Lower Yellow River, it is usual to treat sediment conservation in terms of an entrainment-based (nonequilibrium) rather than a flux-based (equilibrium) formulation with the consideration that fine-grained sediment may be entrained at one place but deposited only at some distant location downstream. However, the differences in prediction between the two formulations are still not well known, and the entrainment formulation may not always be necessary for the Lower Yellow River. Here we study this problem by comparing the results of flux-based and entrainment-based morphodynamics under conditions typical of the Yellow River, using sediment transport equations specifically designed for the Lower Yellow River. We find, somewhat unexpectedly, that in a treatment of a 200-km reach using uniform sediment, there is little difference between the two formulations unless the

  9. Dynamic Analysis of a Rotor System Supported on Squeeze Film Damper with Air Entrainment

    Science.gov (United States)

    Zhang, Wei; Han, Bingbing; Zhang, Kunpeng; Ding, Qian

    2017-12-01

    Squeeze film dampers (SFDs) are widely used in compressors and turbines to suppress the vibration while traversing critical speeds. In practical applications, air ingestion from the outside environment and cavitation may lead to a foamy lubricant that weakens oil film damping and dynamic performance of rotor system. In this paper, a rigid rotor model is established considering both lateral and pitching vibration under different imbalance excitations to evaluate the effect of air entrainment on rotor system. Tests with three different imbalances are carried out on a rotor-SFD apparatus. Volume controlled air in mixture ranging from pure oil to all air are supplied to the SFD. The transient response of rotor is measured in the experiments. The results show that two-phase flow produces significant influence on the system stability and dynamical response. The damping properties are weakened by entrained air, such as the damping on high frequency components of rolling ball bearing. Super-harmonic resonance and bifurcation are observed, as well as the low frequency components due to air entrainment.

  10. New models of droplet deposition and entrainment for prediction of CHF in cylindrical rod bundles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haibin, E-mail: hb-zhang@xjtu.edu.cn [School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Department of Chemical Engineering, Imperial College, London SW7 2BY (United Kingdom); Hewitt, G.F. [Department of Chemical Engineering, Imperial College, London SW7 2BY (United Kingdom)

    2016-08-15

    Highlights: • New models of droplet deposition and entrainment in rod bundles is developed. • A new phenomenological model to predict the CHF in rod bundles is described. • The present model is well able to predict CHF in rod bundles. - Abstract: In this paper, we present a new set of model of droplet deposition and entrainment in cylindrical rod bundles based on the previously proposed model for annuli (effectively a “one-rod” bundle) (2016a). These models make it possible to evaluate the differences of the rates of droplet deposition and entrainment for the respective rods and for the outer tube by taking into account the geometrical characteristics of the rod bundles. Using these models, a phenomenological model to predict the CHF (critical heat flux) for upward annular flow in vertical rod bundles is described. The performance of the model is tested against the experimental data of Becker et al. (1964) for CHF in 3-rod and 7-rod bundles. These data include tests in which only the rods were heated and data for simultaneous uniform and non-uniform heating of the rods and the outer tube. It was shown that the predicted CHFs by the present model agree well with the experimental data and with the experimental observation that dryout occurred first on the outer rods in 7-rod bundles. It is expected that the methodology used will be generally applicable in the prediction of CHF in rod bundles.

  11. Differential entrainment of neuroelectric delta oscillations in developmental dyslexia.

    Directory of Open Access Journals (Sweden)

    Fruzsina Soltész

    Full Text Available Oscillatory entrainment to the speech signal is important for language processing, but has not yet been studied in developmental disorders of language. Developmental dyslexia, a difficulty in acquiring efficient reading skills linked to difficulties with phonology (the sound structure of language, has been associated with behavioural entrainment deficits. It has been proposed that the phonological 'deficit' that characterises dyslexia across languages is related to impaired auditory entrainment to speech at lower frequencies via neuroelectric oscillations (<10 Hz, 'temporal sampling theory'. Impaired entrainment to temporal modulations at lower frequencies would affect the recovery of the prosodic and syllabic structure of speech. Here we investigated event-related oscillatory EEG activity and contingent negative variation (CNV to auditory rhythmic tone streams delivered at frequencies within the delta band (2 Hz, 1.5 Hz, relevant to sampling stressed syllables in speech. Given prior behavioural entrainment findings at these rates, we predicted functionally atypical entrainment of delta oscillations in dyslexia. Participants performed a rhythmic expectancy task, detecting occasional white noise targets interspersed with tones occurring regularly at rates of 2 Hz or 1.5 Hz. Both groups showed significant entrainment of delta oscillations to the rhythmic stimulus stream, however the strength of inter-trial delta phase coherence (ITC, 'phase locking' and the CNV were both significantly weaker in dyslexics, suggestive of weaker entrainment and less preparatory brain activity. Both ITC strength and CNV amplitude were significantly related to individual differences in language processing and reading. Additionally, the instantaneous phase of prestimulus delta oscillation predicted behavioural responding (response time for control participants only.

  12. Cortical entrainment to music and its modulation by expertise.

    Science.gov (United States)

    Doelling, Keith B; Poeppel, David

    2015-11-10

    Recent studies establish that cortical oscillations track naturalistic speech in a remarkably faithful way. Here, we test whether such neural activity, particularly low-frequency (music and whether experience modifies such a cortical phenomenon. Music of varying tempi was used to test entrainment at different rates. In three magnetoencephalography experiments, we recorded from nonmusicians, as well as musicians with varying years of experience. Recordings from nonmusicians demonstrate cortical entrainment that tracks musical stimuli over a typical range of tempi, but not at tempi below 1 note per second. Importantly, the observed entrainment correlates with performance on a concurrent pitch-related behavioral task. In contrast, the data from musicians show that entrainment is enhanced by years of musical training, at all presented tempi. This suggests a bidirectional relationship between behavior and cortical entrainment, a phenomenon that has not previously been reported. Additional analyses focus on responses in the beta range (∼15-30 Hz)-often linked to delta activity in the context of temporal predictions. Our findings provide evidence that the role of beta in temporal predictions scales to the complex hierarchical rhythms in natural music and enhances processing of musical content. This study builds on important findings on brainstem plasticity and represents a compelling demonstration that cortical neural entrainment is tightly coupled to both musical training and task performance, further supporting a role for cortical oscillatory activity in music perception and cognition.

  13. Countercurrent two-phase flow

    International Nuclear Information System (INIS)

    Hewitt, G.F.; Imperial Coll. of Science and Technology, London

    1989-01-01

    A survey is presented of counter-current flow with particular reference to the limits of the regime, namely the 'flooding' phenomena. Emphasis is also given to the transiently counter-current type of flow ('churn flow') which is formed on the break-down of falling film counter-current flow. The mechanisms of flooding are reviewed and flooding in systems with heat transfer and in non-vertical channels is discussed. New data on the flooding phenomena and the region of simultaneous downflow and upflow beyond flooding are presented. The onset of churn flow is discussed and new measurements on churn flow are presented. The characteristics of the churn flow regime are shown to be independent of the coexistence of a falling film region below the liquid injection point. (orig.)

  14. Musical Entrainment Subsumes Bodily Gestures – Its Definition Needs a Spatiotemporal Dimension

    Directory of Open Access Journals (Sweden)

    Marc Leman

    2012-09-01

    Full Text Available In his paper “What is entrainment? Definition and applications in musical research” (this issue, M. Clayton offers a definition of entrainment that is based on a timing dimension (relative phase relationships. However, this definition may be too limited when applied to musical entrainment. Based on the idea that human engagement with music is embodied and that gestures may condition entrainment, I suggest that the definition of entrainment be broadened so as to include a spatiotemporal dimension.

  15. Study on the effect of free acidity and entrained TBP in UNPS on the quality of ADU powder

    International Nuclear Information System (INIS)

    Prudhvi Raju, P.V.S.N.; Mandal, D.

    2015-01-01

    Graphical abstract: From the experimental study it was found that mean particle size of precipitated Ammonium Di-Uranate (ADU) depends on the free acidity content and entrained TBP in Uranyl Nitrate Pure Solution (UNPS). It was found that as the free acidity as well as the entrained TBP content in UNPS increases, mean particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed as shown in below figures. - Highlights: • The mean particle size of precipitated ADU depends on the free acidity in UNPS. • The mean particle size of precipitated ADU also depends on the entrained TBP in UNPS. • As free acidity in UNPS increases, mean particle size of precipitated ADU decreases. • As entrained TBP in UNPS increases, particle size of precipitated ADU decreases. • Based on the experimental results two correlations were developed to find d p of ADU. - Abstract: The mean particle size and size distribution of Ammonium Di-Uranate (ADU) particles, precipitated during the precipitation reaction of Uranyl Nitrate Pure Solution (UNPS) with ammonia play an important role on the sintered density of UO 2 pellets. The quality of precipitated ADU depends on number of process parameters viz., pH of UNPS, concentration of uranium in UNPS, flow rate of ammonium hydroxide, temperature etc. However, the effects of the presence of free acid and entrained Tri-Butyl-Phosphate (TBP) in UNPS on the quality of ADU powder were not studied till date. Experiments were conducted to study the effect of free acidity and the presence of entrained TBP on the quality of precipitated ADU particles. It was found that as the concentration of free acid as well as the concentration of entrained TBP in UNPS increases, the particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed to determine the mean particle size of ADU; one is based on the free acid content of UNPS and the other is based on the

  16. Study on the effect of free acidity and entrained TBP in UNPS on the quality of ADU powder

    Energy Technology Data Exchange (ETDEWEB)

    Prudhvi Raju, P.V.S.N. [Nuclear Fuel Complex, Hyderabad 500 062 (India); Mandal, D., E-mail: dmandal@barc.gov.in [Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2015-09-15

    Graphical abstract: From the experimental study it was found that mean particle size of precipitated Ammonium Di-Uranate (ADU) depends on the free acidity content and entrained TBP in Uranyl Nitrate Pure Solution (UNPS). It was found that as the free acidity as well as the entrained TBP content in UNPS increases, mean particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed as shown in below figures. - Highlights: • The mean particle size of precipitated ADU depends on the free acidity in UNPS. • The mean particle size of precipitated ADU also depends on the entrained TBP in UNPS. • As free acidity in UNPS increases, mean particle size of precipitated ADU decreases. • As entrained TBP in UNPS increases, particle size of precipitated ADU decreases. • Based on the experimental results two correlations were developed to find d{sub p} of ADU. - Abstract: The mean particle size and size distribution of Ammonium Di-Uranate (ADU) particles, precipitated during the precipitation reaction of Uranyl Nitrate Pure Solution (UNPS) with ammonia play an important role on the sintered density of UO{sub 2} pellets. The quality of precipitated ADU depends on number of process parameters viz., pH of UNPS, concentration of uranium in UNPS, flow rate of ammonium hydroxide, temperature etc. However, the effects of the presence of free acid and entrained Tri-Butyl-Phosphate (TBP) in UNPS on the quality of ADU powder were not studied till date. Experiments were conducted to study the effect of free acidity and the presence of entrained TBP on the quality of precipitated ADU particles. It was found that as the concentration of free acid as well as the concentration of entrained TBP in UNPS increases, the particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed to determine the mean particle size of ADU; one is based on the free acid content of UNPS and the other is based on

  17. Nonassociative learning promotes respiratory entrainment to mechanical ventilation.

    Directory of Open Access Journals (Sweden)

    Shawna M MacDonald

    Full Text Available BACKGROUND: Patient-ventilator synchrony is a major concern in critical care and is influenced by phasic lung-volume feedback control of the respiratory rhythm. Routine clinical application of positive end-expiratory pressure (PEEP introduces a tonic input which, if unopposed, might disrupt respiratory-ventilator entrainment through sustained activation of the vagally-mediated Hering-Breuer reflex. We suggest that this potential adverse effect may be averted by two differentiator forms of nonassociative learning (habituation and desensitization of the Hering-Breuer reflex via pontomedullary pathways. METHODOLOGY/PRINCIPAL FINDINGS: We tested these hypotheses in 17 urethane-anesthetized adult Sprague-Dawley rats under controlled mechanical ventilation. Without PEEP, phrenic discharge was entrained 1:1 to the ventilator rhythm. Application of PEEP momentarily dampened the entrainment to higher ratios but this effect was gradually adapted by nonassociative learning. Bilateral electrolytic lesions of the pneumotaxic center weakened the adaptation to PEEP, whereas sustained stimulation of the pneumotaxic center weakened the entrainment independent of PEEP. In all cases, entrainment was abolished after vagotomy. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate an important functional role for pneumotaxic desensitization and extra-pontine habituation of the Hering-Breuer reflex elicited by lung inflation: acting as buffers or high-pass filters against tonic vagal volume input, these differentiator forms of nonassociative learning help to restore respiratory-ventilator entrainment in the face of PEEP. Such central sites-specific habituation and desensitization of the Hering-Breuer reflex provide a useful experimental model of nonassociative learning in mammals that is of particular significance in understanding respiratory rhythmogenesis and coupled-oscillator entrainment mechanisms, and in the clinical management of mechanical ventilation in

  18. The entrainment of air by water jet impinging on a free surface

    Energy Technology Data Exchange (ETDEWEB)

    Soh, Wee King [University of Wollongong, School of Mechanical, Materials and Mechatronics Engineering, Northfields Ave, NSW (Australia); Khoo, Boo Cheong [National University of Singapore, Department of Mechanical and Production Engineering, 10 Kent Ridge Crescent (Singapore); Yuen, W.Y. Daniel [BlueScope Steel Research, Port Kembla, NSW (Australia)

    2005-09-01

    High-speed cine and video photographs were used to capture the flow patterns of a column of water jet impinging into a pool of water. The impact results in air entrainment into water in the form of a void with no mixing between the water in the jet and the surrounding water. Conservation of fluid momentum shows that the rate of increase of the height of the air void depends on the drag coefficient of the jet front. By neglecting the frictional losses, the application of energy conservation yields an expression that relates the maximum height of the air void with the properties of the water jet. (orig.)

  19. Pollutant Removal, Dispersion and Entrainment over Two-Dimensional Idealized Street Canyons: an LES Approach

    Science.gov (United States)

    Wong, C.; Liu, C.

    2010-12-01

    Unlike pollutant transport over flat terrain, the mechanism and plume dispersion over urban areas is not well known. This study is therefore conceived to examine how urban morphology modifies the pollutant transport over urban areas. The computational domain and boundary condition used in this study is shown in Figure 1. The LES shows that inside the street canyon, the ground-level pollutants are carried to roof-level by the re-circulating flow, which are then removed from the street canyon to the UBL. Right above the roof level, narrow high-speed air masses in the streamwise flows and intensive downdrafts have been found in the shear layer. Different from the flows over a smooth surface, the maximum turbulence intensities descend that are peaked near the top of the building roughness. The pollutant is rather uniformly distributed inside a street canyon but disperses rapidly over the buildings exhibiting a Gaussian-plume form in the UBL. The mean component of vertical pollutant flux shows that the mean wind contributes to pollutant removal and entrainment simultaneously. Whereas, the fluctuating component demystifies that pollutant removal is mainly governed by atmospheric turbulence. Over the roof level, atmospheric flows slow down rapidly in the wake behind leeward building, suggesting the momentum entrainment into the street canyons. The decelerating streamwise flows in turn lead to upward flows carrying pollutants away from the street canyons, illustrating the basic pollutant removal mechanism in the skimming flow regime. Figure 1: Computational domain and boundary conditions Figure 2: Ensemble average vertical pollutant flux along the roof level. (a). Mean component; (b). turbulent component.

  20. Cyclonic entrainment of preconditioned shelf waters into a frontal eddy

    Science.gov (United States)

    Everett, J. D.; Macdonald, H.; Baird, M. E.; Humphries, J.; Roughan, M.; Suthers, I. M.

    2015-02-01

    The volume transport of nutrient-rich continental shelf water into a cyclonic frontal eddy (entrainment) was examined from satellite observations, a Slocum glider and numerical simulation outputs. Within the frontal eddy, parcels of water with temperature/salinity signatures of the continental shelf (18-19°C and >35.5, respectively) were recorded. The distribution of patches of shelf water observed within the eddy was consistent with the spiral pattern shown within the numerical simulations. A numerical dye tracer experiment showed that the surface waters (≤50 m depth) of the frontal eddy are almost entirely (≥95%) shelf waters. Particle tracking experiments showed that water was drawn into the eddy from over 4° of latitude (30-34.5°S). Consistent with the glider observations, the modeled particles entrained into the eddy sunk relative to their initial position. Particles released south of 33°S, where the waters are cooler and denser, sunk 34 m deeper than their release position. Distance to the shelf was a critical factor in determining the volume of shelf water entrained into the eddy. Entrainment reduced to 0.23 Sv when the eddy was furthest from the shelf, compared to 0.61 Sv when the eddy was within 10 km of the shelf. From a biological perspective, quantifying the entrainment of shelf water into frontal eddies is important, as it is thought to play a significant role in providing an offshore nursery habitat for coastally spawned larval fish.

  1. Entrainment of Spontaneously Hypertensive Rat Fibroblasts by Temperature Cycles

    Science.gov (United States)

    Sládek, Martin; Sumová, Alena

    2013-01-01

    The functional state of the circadian system of spontaneously hypertensive rats (SHR) differs in several characteristics from the functional state of normotensive Wistar rats. Some of these changes might be due to the compromised ability of the central pacemaker to entrain the peripheral clocks. Daily body temperature cycles represent one of the important cues responsible for the integrity of the circadian system, because these cycles are driven by the central pacemaker and are able to entrain the peripheral clocks. This study tested the hypothesis that the aberrant peripheral clock entrainment of SHR results from a compromised peripheral clock sensitivity to the daily temperature cycle resetting. Using cultured Wistar rat and SHR fibroblasts transfected with the circadian luminescence reporter Bmal1-dLuc, we demonstrated that two consecutive square-wave temperature cycles with amplitudes of 2.5°C are necessary and sufficient to restart the dampened oscillations and entrain the circadian clocks in both Wistar rat and SHR fibroblasts. We also generated a phase response curve to temperature cycles for fibroblasts of both rat strains. Although some of the data suggested a slight resistance of SHR fibroblasts to temperature entrainment, we concluded that the overall effect it too weak to be responsible for the differences between the SHR and Wistar in vivo circadian phenotype. PMID:24116198

  2. Entrainment of ichthyoplankton and larval fishes during cooling water withdrawal

    International Nuclear Information System (INIS)

    McFarlane, R.W.

    1978-01-01

    Plantonic fish eggs and larvae are entrained into the Savannah River Plant (SRP) pumping system as Savannah River water is withdrawn for cooling purposes. The American shad contributed 96% of the planktonic fish eggs collected in the Savannah River. Eggs were rare in plankton samples from the intake canals and were assumed to have settled to the bottom as current velocity was reduced in the canal entrance. An estimated 72 million fish eggs were transported past the intake canals. Assuming ''worst case conditions,'' 6.8 million eggs (9.5%) could have been lost due to entrainment. Blueback herring comprised nearly one-half of the 216 million fish larvae susceptible to impact. Spotted sucker and black crappie were also common among the 22 species of fish larvae collected. An estimated 19.6 million (9.1%) fish larvae could have been entrained under ''worst case conditions''

  3. Rewetting and liquid entrainment during reflooding: state of the art

    International Nuclear Information System (INIS)

    Elias, E.; Yadigaroglu, G.

    1977-05-01

    Considerable interest has recently been generated in the problems of surface rewetting and the physics of liquid droplet entrainment due to their role in light water nuclear reactor safety. Published models of the rewetting process include simple one-dimensional solutions in two axial regions, one-dimensional solutions in three axial regions with or without precursory cooling, one- and two-dimensional numerical-difference techniques using temperature dependent heat transfer coefficients, and analytical two-dimensional solutions. The basic assumptions of these models and the numerical values assigned to the various parameters, as well as empirical rewetting correlations, are discussed. The various mechanisms for liquid droplet entrainment and analytical formulations of the critical gas velocity and of the droplet diameter at the onset of entrainment are reviewed

  4. Treatment of high-strength wastewater in tropical constructed wetlands planted with Sesbania sesban: Horizontal subsurface flow versus vertical downflow

    DEFF Research Database (Denmark)

    Dan, Truong Hoang; Quang, Le Nhat; Chiem, Nguyen Huu

    2011-01-01

    Treatment of various types of wastewaters is an urgent problem in densely populated areas of many tropical countries. We studied the potential of using Sesbania sesban, an N2-fixing shrub, in constructed wetland systems for the treatment of high-strength wastewater. A replicated horizontal subsur...

  5. Suitability assessment of grey water quality treated with an upflow-downflow siliceous sand/marble waste filtration system for agricultural and industrial purposes.

    Science.gov (United States)

    Chaabane, Safa; Riahi, Khalifa; Hamrouni, Hédi; Thayer, Béchir Ben

    2017-04-01

    The present study examines the suitability assessment of an upflow-downflow siliceous sand/marble waste filtration system for treatment and reuse of grey water collected from bathrooms of the student residential complex at the Higher Institute of Engineering Medjez El Bab (Tunisia). Once the optimization of grey water pre-treatment system has been determined, the filtration system was operated at different hydraulic loading rate and media filter proportions in order to assess the suitability of treated grey water for irrigational purpose according to salinity hazard, sodium hazard, magnesium hazard, permeability index, water infiltration rate, and widely used graphical methods. Suitability of the treated grey water for industrial purpose was evaluated in terms of foaming, corrosion, and scaling. Under optimal operational conditions, results reveals that treated grey water samples with an upflow-downflow siliceous sand/marble waste filtration system may be considered as a good and an excellent water quality suitable for irrigation purpose. However, treated grey water was found not appropriate for industrial purpose due to high concentrations of calcium and sodium that can generate foaming and scaling harm to boilers. These results suggest that treated grey water with an upflow-downflow siliceous sand/marble waste filtration system would support production when used as irrigation water.

  6. Method and apparatus for controlling the flow rate of mercury in a flow system

    Science.gov (United States)

    Grossman, Mark W.; Speer, Richard

    1991-01-01

    A method for increasing the mercury flow rate to a photochemical mercury enrichment utilizing an entrainment system comprises the steps of passing a carrier gas over a pool of mercury maintained at a first temperature T1, wherein the carrier gas entrains mercury vapor; passing said mercury vapor entrained carrier gas to a second temperature zone T2 having temperature less than T1 to condense said entrained mercury vapor, thereby producing a saturated Hg condition in the carrier gas; and passing said saturated Hg carrier gas to said photochemical enrichment reactor.

  7. Wind profiler mixing depth and entrainment measurements with chemical applications

    Energy Technology Data Exchange (ETDEWEB)

    Angevine, W.M.; Trainer, M.; Parrish, D.D.; Buhr, M.P.; Fehsenfeld, F.C. [NOAA Aeronomy Lab., Boulder, CO (United States); Kok, G.L. [NCAR Research Aviation Facility, Boulder, CO (United States)

    1994-12-31

    Wind profiling radars operating at 915 MHz have been present at a number of regional air quality studies. The profilers can provide a continuous, accurate record of the depth of the convective mixed layer with good time resolution. Profilers also provide information about entrainment at the boundary layer top. Mixing depth data from several days of the Rural Oxidants in the Southern Environment II (ROSE II) study in Alabama in June, 1992 are presented. For several cases, chemical measurements from aircraft and ground-based instruments are shown to correspond to mixing depth and entrainment zone behavior observed by the profiler.

  8. Particle Entrainment in Spherical-Cap Wakes

    Energy Technology Data Exchange (ETDEWEB)

    Warncke, Norbert G W; Delfos, Rene; Ooms, Gijs; Westerweel, Jerry, E-mail: n.g.w.warncke@tudelft.nl [Laboratory for Aero- and Hydrodynamics, Delft University of Technology (Netherlands)

    2011-12-22

    In this work we study the preferential concentration of small particles in the turbulent wake behind a spherical-cap object. We present a model predicting the mean particle concentration in the near-wake as a function of the characteristic Stokes number of the problem, the turbulence level and the Froude number. We compare the model with our experimental results on this flow, measured in a vertical water tunnel.

  9. RELAP5/MOD3 analysis of a heated channel in downflow

    International Nuclear Information System (INIS)

    Dimenna, R.A.; Qureshi, Z.H.; Boman, A.L.

    1993-01-01

    The onset of flow instability (OFI) is a significant phenomenon affecting the determination of a safe operating power limit in the Savannah River Site production reactors. Tests performed at Columbia University for a single tube with uniform axial and azimuthal heating have been analyzed with RELAP5/NPR, Version 0, a version of RELAP5/MOD3. The tests include water flow rates from 3.2 x l0 -4 - 2.l x 10 -3 m 3 /s (5 - 33 gpm), Reynolds numbers from 30,000 - 400,000, and surface heat fluxes from 0 - 3.2 x l0 6 w/m 2 (0 - 1,000,000 Btu/hr- ft 2 ). Pressure drop versus flow rate curves were mapped for both fixed pressure boundary conditions and fixed flow boundary conditions. RELAP5/MOD3 results showed fair agreement with data for both types of boundary conditions, and good internal consistency between calculations using the two different types of boundary conditions. Under single-phase unheated conditions, the code overpredicted the pressure drop by 22 - 34%. Under single-phase heated conditions, the overprediction increased to as much as 55%. For those tests where two-phase conditions were observed at the channel exit, RELAP5 predicted lower flows than seen in the tests before voiding occurred

  10. On the entrainment of solid particles from a fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Sciazko, M. (Institute of Chemical Processing of Coal, Zabrze (Poland)); Bandrowski, J.; Raczek, J. (Politechnika Slaska, Gliwice (Poland). Inst. of Chemical Engineering and Apparatus Construction)

    1991-04-01

    This paper presents a generalized approach to the phenomenon of entrainment of solids from a fluidized bed. Starting with the discussion of the transport disengaging height (TDH) and of the elutriation of particles above the TDH, one arrives finally at the relationship between the elutriation rate constant, saturation carrying capacity and choking parameters of pneumatic transport. (orig.).

  11. Development and entrainment of the colonic circadian clock during ontogenesis

    Czech Academy of Sciences Publication Activity Database

    Polidarová, Lenka; Olejníková, Lucie; Paušlyová, Lucia; Sládek, Martin; Soták, Matúš; Pácha, Jiří; Sumová, Alena

    2014-01-01

    Roč. 306, č. 4 (2014), G346-G356 ISSN 0193-1857 R&D Projects: GA ČR(CZ) GAP303/12/1108 Institutional support: RVO:67985823 Keywords : circadian clock * clock gene * ontogenesis * circadian entrainment Subject RIV: ED - Physiology Impact factor: 3.798, year: 2014

  12. Historical development of entrainment models for Hudson River striped bass

    International Nuclear Information System (INIS)

    Christensen, S.W.; Englert, T.L.

    1988-01-01

    In the mid-1960s, concerns surfaced regarding entrainment and impingement of young-of-the-year (age-0) striped bass by electric power generating facilities on the Hudson River. These concerns stimulated the development of increasingly complex models to evaluate the impacts of these facilities. The earliest simplistic formulas, based on empirical data, proved inadequate because of conceptual shortcomings, incomplete development, and lack of data. By 1972, complex transport models based on biological and hydrodynamic principles had been developed and applied by scientists representing both the utilities and the government. Disagreements about the acceptability of these models spurred the development of even more complex models. The entrainment models stimulated the collection of substantial amounts of field data to define the spatial distributions and entrainment survival of early life stages. As the difficulties of accounting for the movement of early life stages from hydrodynamic principles became more evident and as more field data became available, simpler empirical modeling approaches became both practical and defensible. Both empirical and hydrodynamic modeling approaches were applied during the US Environmental Protection Agency's hearings on the Hudson River power case (1977-1980). The main lessons learned from the experience with entrainment-impingement modeling are that complex mechanistic models are not necessarily better than simpler empirical models for young fish, and that care must be taken to construct even the simple models correctly. 29 refs., 4 figs., 1 tab

  13. Entrainment to an auditory signal: Is attention involved?

    NARCIS (Netherlands)

    Kunert, R.; Jongman, S.R.

    2017-01-01

    Many natural auditory signals, including music and language, change periodically. The effect of such auditory rhythms on the brain is unclear however. One widely held view, dynamic attending theory, proposes that the attentional system entrains to the rhythm and increases attention at moments of

  14. Queueing-Based Synchronization and Entrainment for Synthetic Gene Oscillators

    Science.gov (United States)

    Mather, William; Butzin, Nicholas; Hochendoner, Philip; Ogle, Curtis

    Synthetic gene oscillators have been a major focus of synthetic biology research since the beginning of the field 15 years ago. They have proven to be useful both for biotechnological applications as well as a testing ground to significantly develop our understanding of the design principles behind synthetic and native gene oscillators. In particular, the principles governing synchronization and entrainment of biological oscillators have been explored using a synthetic biology approach. Our work combines experimental and theoretical approaches to specifically investigate how a bottleneck for protein degradation, which is present in most if not all existing synthetic oscillators, can be leveraged to robustly synchronize and entrain biological oscillators. We use both the terminology and mathematical tools of queueing theory to intuitively explain the role of this bottleneck in both synchronization and entrainment, which extends prior work demonstrating the usefulness of queueing theory in synthetic and native gene circuits. We conclude with an investigation of how synchronization and entrainment may be sensitive to the presence of multiple proteolytic pathways in a cell that couple weakly through crosstalk. This work was supported by NSF Grant #1330180.

  15. Efficiency of brainwave entrainment by binaural beats in reducing anxiety

    Directory of Open Access Journals (Sweden)

    Ahmad Alipoor

    2014-04-01

    Full Text Available Background: Anxiety is a fundamental phenomenon that is a common symptom in all mental disorders. The aim of the present study was to assess the effect of brainwave entrainment on anxiety reduction using binaural beats. Methods: In this experimental double-blind study, 30 employees were selected from an engineering research firm through random sampling and replacement and divided into two groups: control group and experimental group. All participants completed the Spielberger’s State-Trait Anxiety Inventory (STAI. Then, the experimental group listened to binaural beats which was recorded on a non-vocal piece of music for 4 weeks, 3 sessions each week. Each session lasted about 20 minutes. At the same time, the control group listened to the background music without any entrainment sound. At the end, both groups completed the anxiety questionnaire and the anxiety scores of both groups obtained before and after intervention were analyzed by ANCOVA. Results: The findings showed that the brainwave entrainment using binaural beats led to the significant reduction of state anxiety (P<0.001 and trait anxiety (P<0.018. Conclusion: Brainwave entrainment using binaural beats is an effective factor in decreasing state and trait anxiety; so, it can be used to reduce anxiety in mental health centers.

  16. Conversational quality is affected by and reflected in prosodic entrainment

    DEFF Research Database (Denmark)

    Michalsky, Jan; Niebuhr, Oliver; Schoormann, Heike

    2018-01-01

    Prosodic entrainment is connected to various forms of communicative success. One possibility to assess successful communication in non-task-oriented everyday conversations is through the participants’ perception of conversational quality. In this study we investigate whether a speaker’s degree of...

  17. Surf zone entrainment, along-shore transport, and human health implications of pollution from tidal outlets

    Science.gov (United States)

    Grant, S. B.; Kim, J. H.; Jones, B. H.; Jenkins, S. A.; Wasyl, J.; Cudaback, C.

    2005-10-01

    Field experiments and modeling studies were carried out to characterize the surf zone entrainment and along-shore transport of pollution from two tidal outlets that drain into Huntington Beach and Newport Beach, popular public beaches in southern California. The surf zone entrainment and near-shore transport of pollutants from these tidal outlets appears to be controlled by prevailing wave conditions and coastal currents, and fine-scale features of the flow field around the outlets. An analysis of data from dye experiments and fecal indicator bacteria monitoring studies reveals that the along-shore flux of surf zone water is at least 50 to 300 times larger than the cross-shore flux of surf zone water. As a result, pollutants entrained in the surf zone hug the shore, where they travel significant distances parallel to the beach before diluting to extinction. Under the assumption that all surf zone pollution at Huntington Beach originates from two tidal outlets, the Santa Ana River and Talbert Marsh outlets, models of mass and momentum transport in the surf zone approximately capture the observed tidal phasing and magnitude of certain fecal indicator bacteria groups (total coliform) but not others (Escherichia coli and enterococci), implying the existence of multiple sources of, and/or multiple transport pathways for, fecal pollution at this site. The intersection of human recreation and near-shore pollution pathways implies that, from a human health perspective, special care should be taken to reduce the discharge of harmful pollutants from land-side sources of surface water runoff, such as tidal outlets and storm drains.

  18. Large Eddy Simulations of sediment entrainment induced by a lock-exchange gravity current

    Science.gov (United States)

    Kyrousi, Foteini; Leonardi, A.; Roman, F.; Armenio, V.; Zanello, F.; Zordan, J.; Juez, C.; Falcomer, L.

    2018-04-01

    Large Eddy simulations of lock-exchange gravity currents propagating over a mobile reach are presented. The numerical setting allows to investigate the sediment pick up induced by the currents and to study the underlying mechanisms leading to sediment entrainment for different Grashof numbers and grain sizes. First, the velocity field and the bed shear-stress distribution are investigated, along with turbulent structures formed in the flow, before the current reaches the mobile bed. Then, during the propagation of the current above the erodible section of the bed the contour plots of the entrained material are presented as well as the time evolution of the areas covered by the current and by the sediment at this section. The numerical outcomes are compared with experimental data showing a very good agreement. Overall, the study confirms that sediment pick up is prevalent at the head of the current where the strongest turbulence occurs. Further, above the mobile reach of the bed, settling process seems to be of minor importance, with the entrained material being advected downstream by the current. Additionally, the study shows that, although shear stress is the main mechanism that sets particles in motion, turbulent bursts as well as vertical velocity fluctuations are also necessary to counteract the falling velocity of the particles and maintain them into suspension. Finally, the analysis of the stability conditions of the current shows that, from one side, sediment concentration gives a negligible contribution to the stability of the front of the current and from the other side, the stability conditions provided by the current do not allow sediments to move into the ambient fluid.

  19. Characterization of liquid entrainment in the AP1000 automatic depressurization system from APEX tests

    International Nuclear Information System (INIS)

    Richard F Wright; Terry L Schulz; Jose N Reyes; John Groome

    2005-01-01

    -phase flow in the ADS-4, and to quantify the liquid entrainment at high decay power conditions representing the time of ADS-4 actuation, and at low decay power conditions representing the time of IRWST and sump injection. For the higher power levels, the tests show that as long as core makeup water is available, the two phase mixture level remains at the hot leg elevation, and a significant amount of liquid is entrained out the ADS-4 lines. As the makeup flow is decreased (at a given power level), the collapsed liquid level decreased as the core exit void fraction increased, but the two-phase level remains in the hot leg. If the makeup flow is stopped, the two-phase level falls below the hot leg elevation, and the liquid entrainment is markedly reduced. At the low power levels, the core makeup flow is sufficient to assure that the two-phase mixture level remains at the hot leg elevation, and significant liquid entrainment is observed even at very low steam velocities. (authors)

  20. Simulating the impact of the entrainment of winter flounder larvae

    International Nuclear Information System (INIS)

    Hess, K.W.; Sissenwine, M.P.; Saila, S.B.

    1975-01-01

    The transport of winter flounder larvae around the Millstone Point, Conn. Area by the action of tidal currents and diffusion was simulated by computer to predict the numbers which could be entrained during the operation of a local nuclear power station. A tidal hydrodynamic model with variable depth was employed to simulate currents and water levels. These techniques provided input to a transport model which simulated the concentration of larvae. A larval source in a tributary river was simulated for twenty tidal cycles, with and without entrainment. The results indicated that the reduction in winter flounder larvae near Millstone Point at the end of the pelagic stage (period during which larvae are likely to be entrained) was less than 1 percent when it was assumed that larvae have little chance of returning once lost from Millstone bight. In order to assess the effect of a 1 percent reduction in recruitment of winter flounder larvae to the benthic phase of their life cycle, the local population was simulated by a model in which year-classes and the total egg production were represented by compartments. Each year-class grew, produced eggs, suffered natural and fishing mortality according to information derived from the literature. The effect of power plant entrainment was incorporated by reducing the number of recruits to year-class I that would normally result from a specific level of egg production. For a 1 percent reduction in recruitment due to power plant entrainment, a potential 6 percent decrease in total population size following 35 years of operation was indicated. (U.S.)

  1. Assessment of ichthyoplankton entrainment at Pickering 'A' NGS using a pump/net in lake system

    International Nuclear Information System (INIS)

    McKinley, R.S.

    1985-03-01

    Annual entrainment at Pickering 'A' NGS was estimated for alewife as 13.6 X 10 6 larvae and 409 X 10 6 eggs. A substantial portion of eggs and larvae entering the intake were dead due to natural mortality (41%-81%) prior to entrainment. Viable eggs and larvae, immediately following entrainment showed mortalities of 54% and 44% respectively. The latent mortality of entrained eggs was 100% (48 h)

  2. Numerical investigation on the gas entrainment rate on ventilated supercavity body

    Directory of Open Access Journals (Sweden)

    WuGang Yang

    2016-12-01

    Full Text Available The supercavitation technique provides a means of significantly increasing the velocity of an underwater vehicle. This technique involves essentially the creation of stable supercavity shape. The method of artificial ventilation is most effective for generating and dominating the supercavity. This paper focuses on the numerical simulation of flow field around three-dimensional body. The method is based on the multiphase computational fluid dynamics model combined with the turbulence model and the full cavity model. The fundamental similarity parameters of ventilated supercavity flows that include cavitation number, Froude number Fr, entrainment rate CQ, and drag coefficient Cx are all investigated numerically in the case of steady flow and gravity field. We discuss the following simulations results in three parts: (1 the variations of the cavitation number and the supercavity’s relative diameter with entrainment rate; (2 the drag coefficient versus the cavitation number; and (3 deformation of supercavity axis caused by gravitational effect for three different fixed three Froude numbers. In the full paper, we give the comparison results of the drag reduction ratio among numerical simulation and experiment conducted in hydrodynamic tunnel and towing tank, respectively. We summarize our discussion of gravitational effect on the axis deformation of supercavity as follows: in the case of smaller Froude number, the inclination of the cavity axis increases monotonously with increasing horizontal length and reaches its maximal value at the end of supercavity; this deformation can be almost completely negligible when the Froude number Fr is larger than 7.0. The comparisons with the experimental data in the hydrodynamic tunnel and the towing tank indicate that the present method is effective for predicting the flows around ventilated supercavity; that the numerical results is in good agreement with the experimental ones and that the maximal value of the

  3. The effect of low-NOx combustion on residual carbon in fly ash and its adsorption capacity for air entrainment admixtures in concrete

    DEFF Research Database (Denmark)

    Pedersen, Kim Hougaard; Jensen, Anker Degn; Dam-Johansen, Kim

    2010-01-01

    been combusted in an entrained flow reactor to test the impact of changes in operating conditions and fuel type on the AEA adsorption of ash and NOx formation. Increased oxidizing conditions, obtained by improved fuel-air mixing or higher excess air, decreased the AEA requirements of the produced ash......Fly ash from pulverized coal combustion contains residual carbon that can adsorb the air-entraining admixtures (AEAs) added to control the air entrainment in concrete. This is a problem that has increased by the implementation of low-NOx combustion technologies. In this work, pulverized fuel has...... by up to a factor of 25. This was due to a lower carbon content in the ash and a lower specific AEA adsorptivity of the carbon. The latter was suggested to be caused by changes in the adsorption properties of the unburned char and a decreased formation of soot, which was found to have a large AEA...

  4. The influence of Savannah River discharge and changing SRS cooling water requirements on the potential entrainment of ichthyoplankton at the SRS Savannah River intakes

    International Nuclear Information System (INIS)

    Paller, M.H.

    1992-08-01

    Entrainment (i.e., withdrawal of fish larvae and eggs in cooling water) at the SRS Savannah River intakes is greatest when periods of high river water usage coincide with low river dischargeduring the spawning season. American shad and striped bass are the two species of greatest concern because of their recreational and/or commercial importance and because they produce drifting eggs and larvae vulnerable to entrainment. In the mid-reaches of the Savannah River, American shad and striped bass spawn primarily during April and May. An analysis of Savannah River discharge during April and May 1973--1989 indicated the potential for entrainment of 4--18% of the American shad and striped bass larvae and eggs that drifted past the SRS. This analysis assumed the concurrent operation of L-, K-, and P-Reactors. Additional scenarios investigated were: (1) shutting down L- and P-Reactors, and operating K-Reactor with a recycle cooling tower; and (2) shutting down L- and P-Reactors, eliminating minimum flows to Steel Creek, and operating K-Reactor with a recycle cooling tower. The former scenario reduced potential entrainment to 0.7--3.3%, and the latter scenario reduced potential entrainment to 0.20.8%. Thus, the currently favored scenario of operating K-Reactor with a cooling tower and not operating L- and P-Reactors represents a significant lessening of the impact of SRS operations

  5. New insights on entrainment and condensation in volcanic plumes: Constraints from independent observations of explosive eruptions and implications for assessing their impacts

    Science.gov (United States)

    Aubry, Thomas J.; Jellinek, A. Mark

    2018-05-01

    The turbulent entrainment of atmosphere and the condensation of water vapor govern the heights of explosive volcanic plumes. These processes thus determine the delivery and the lifetime of volcanic ash and aerosols into the atmosphere. Predictions of plume heights using one-dimensional "integral" models of volcanic plumes, however, suffer from very large uncertainties, related to parameterizations for entrainment and condensation. In particular, the wind entrainment coefficient β, which governs the contribution of crosswinds to turbulent entrainment, is subject to uncertainties of one order of magnitude, leading to relative uncertainties of the order of 50% on plume height. In this study, we use a database of 94 eruptive phases with independent estimates of mass eruption rate and plume height to constrain and evaluate four popular 1D models. We employ re-sampling methods to account for observational uncertainties. We show that plume height predictions are significantly improved when: i) the contribution of water vapor condensation to the plume buoyancy flux is excluded; and ii) the wind entrainment coefficient β is held constant between 0.1 and 0.4. We explore implications of these results for predicting the climate impacts of explosive eruptions and the likelihood that eruptions will form stable umbrella clouds or devastating pyroclastic flows. Last, we discuss the sensitivity of our results to the definition of plume height in the model in light of a recent set of laboratory experiments and draw conclusions for improving future databases of eruption parameters.

  6. Relativistic mean field model for entrainment in general relativistic superfluid neutron stars

    International Nuclear Information System (INIS)

    Comer, G.L.; Joynt, R.

    2003-01-01

    General relativistic superfluid neutron stars have a significantly more intricate dynamics than their ordinary fluid counterparts. Superfluidity allows different superfluid (and superconducting) species of particles to have independent fluid flows, a consequence of which is that the fluid equations of motion contain as many fluid element velocities as superfluid species. Whenever the particles of one superfluid interact with those of another, the momentum of each superfluid will be a linear combination of both superfluid velocities. This leads to the so-called entrainment effect whereby the motion of one superfluid will induce a momentum in the other superfluid. We have constructed a fully relativistic model for entrainment between superfluid neutrons and superconducting protons using a relativistic σ-ω mean field model for the nucleons and their interactions. In this context there are two notions of 'relativistic': relativistic motion of the individual nucleons with respect to a local region of the star (i.e. a fluid element containing, say, an Avogadro's number of particles), and the motion of fluid elements with respect to the rest of the star. While it is the case that the fluid elements will typically maintain average speeds at a fraction of that of light, the supranuclear densities in the core of a neutron star can make the nucleons themselves have quite high average speeds within each fluid element. The formalism is applied to the problem of slowly rotating superfluid neutron star configurations, a distinguishing characteristic being that the neutrons can rotate at a rate different from that of the protons

  7. Watershed wash-off of atmospherically deposited radionuclides: a review of normalized entrainment coefficients

    International Nuclear Information System (INIS)

    Garcia-Sanchez, L.; Konoplev, A.V.

    2009-01-01

    Radionuclide wash-off is the transport of activity by flowing water over the soil surface (runoff). To complete existing reviews on long-term removal rates, this paper focuses on short-term wash-off fluxes, quantified in the literature by soil-runoff transfer factors called normalized liquid and solid entrainment coefficients (noted K l *, K s *). Compiled data concerned essentially 137 Cs and 90 Sr wash-off measured under simulated rainfalls on small experimental plots after Chernobyl fallout in the exclusion zone. K l * and K s * values span approximately one order of magnitude. Their validity is limited to a season, and their representativeness is limited by restricted studied situations, notably dominant unsoluble forms in fallout, light soils and intense rainfalls. Formulas based on a simplified representation of the soil-runoff system were proposed to generalize the existing values for other conditions. However, their implementation requires a more systematic compilation of the available information, including decisive influence factors such as the fraction of exchangeable form, distribution coefficient, suspended matter enrichment ratio. Entrainment coefficients K l * and K s * were mathematically related to the transfer function approach. The proposed relationships proved their complementarity in terms of time support and captured fluctuations. Both approaches should be used in assessments to estimate average fluxes and their variability.

  8. Biological evaluation of devices used for reducing entrainment and impingement losses at thermal power plants

    International Nuclear Information System (INIS)

    Cada, G.F.; Szluha, A.T.

    1978-01-01

    A preliminary survey of fish protection devices either in use or proposed for water intake structures was conducted for the purpose of assessing their potential for reducing impingement and entrainment. All the designs examined can be divided into two basic categories: behavioral screening systems and physical screening systems. The behavioral screening devices rely upon the ability of fish to sense artificial stimuli and respond by swimming away from hazardous areas. These systems are of little or no value in protecting planktonic fish eggs, larvae, and disoriented, heat-shocked, or lethargic adult fishes. Many of the physical screening devices, on the other hand, require the impingement of organisms against a screen before they can be removed from the intake system, thus subjecting survival. Some of the designs incorporate both behavioral and physical sceening concepts. Six devices were selected for further consideration based on their potential or demonstrated effectiveness in reducing impingement and entrainment losses at a variety of intake situations. The structures evaluated were modified vertical traveling screens, louvers, angled vertical traveling screens, horizontal traveling screens, center-flow screens, and wedge-wire screens. Since some of these intake structures represent new concepts, few laboratory or in situ biological studies have been carried out. For others, actual reductions in fish losses have been demonstrated. The design features and status of biological testing is discussed for each device, and an evaluation of their fish protection potential is presented

  9. Linear predictions of supercritical flow instability in two parallel channels

    International Nuclear Information System (INIS)

    Shah, M.

    2008-01-01

    A steady state linear code that can predict thermo-hydraulic instability boundaries in a two parallel channel system under supercritical conditions has been developed. Linear and non-linear solutions of the instability boundary in a two parallel channel system are also compared. The effect of gravity on the instability boundary in a two parallel channel system, by changing the orientation of the system flow from horizontal flow to vertical up-flow and vertical down-flow has been analyzed. Vertical up-flow is found to be more unstable than horizontal flow and vertical down flow is found to be the most unstable configuration. The type of instability present in each flow-orientation of a parallel channel system has been checked and the density wave oscillation type is observed in horizontal flow and vertical up-flow, while the static type of instability is observed in a vertical down-flow for the cases studied here. The parameters affecting the instability boundary, such as the heating power, inlet temperature, inlet and outlet K-factors are varied to assess their effects. This study is important for the design of future Generation IV nuclear reactors in which supercritical light water is proposed as the primary coolant. (author)

  10. Microparticle Flow Sensor

    Science.gov (United States)

    Morrison, Dennis R.

    2005-01-01

    The microparticle flow sensor (MFS) is a system for identifying and counting microscopic particles entrained in a flowing liquid. The MFS includes a transparent, optoelectronically instrumented laminar-flow chamber (see figure) and a computer for processing instrument-readout data. The MFS could be used to count microparticles (including micro-organisms) in diverse applications -- for example, production of microcapsules, treatment of wastewater, pumping of industrial chemicals, and identification of ownership of liquid products.

  11. Bed-material entrainment and associated transportation infrastructure problems in streams of the Edwards Plateau, central Texas

    Science.gov (United States)

    Heitmuller, Franklin T.; Asquith, William H.

    2008-01-01

    The Texas Department of Transportation commonly builds and maintains low-water crossings (LWCs) over streams in the Edwards Plateau in Central Texas. LWCs are low-height structures, typically constructed of concrete and asphalt, that provide acceptable passage over seasonal rivers or streams with relatively low normal-depth flow. They are designed to accommodate flow by roadway overtopping during high-flow events. The streams of the Edwards Plateau are characterized by cobble- and gravel-sized bed material and highly variable flow regimes. Low base flows that occur most of the time occasionally are interrupted by severe floods. The floods entrain and transport substantial loads of bed material in the stream channels. As a result, LWCs over streams in the Edwards Plateau are bombarded and abraded by bed material during floods and periodically must be maintained or even replaced.

  12. Universal entrainment mechanism controls contact times with motile cells

    Science.gov (United States)

    Mathijssen, Arnold J. T. M.; Jeanneret, Raphaël; Polin, Marco

    2018-03-01

    Contact between particles and motile cells underpins a wide variety of biological processes, from nutrient capture and ligand binding to grazing, viral infection, and cell-cell communication. The window of opportunity for these interactions depends on the basic mechanism determining contact time, which is currently unknown. By combining experiments on three different species—Chlamydomonas reinhardtii, Tetraselmis subcordiforms, and Oxyrrhis marina—with simulations and analytical modeling, we show that the fundamental physical process regulating proximity to a swimming microorganism is hydrodynamic particle entrainment. The resulting distribution of contact times is derived within the framework of Taylor dispersion as a competition between advection by the cell surface and microparticle diffusion, and predicts the existence of an optimal tracer size that is also observed experimentally. Spatial organization of flagella, swimming speed, and swimmer and tracer size influence entrainment features and provide tradeoffs that may be tuned to optimize the estimated probabilities for microbial interactions like predation and infection.

  13. A new technology for air-entrainment of concrete

    DEFF Research Database (Denmark)

    Laustsen, Sara; Hasholt, Marianne Tange; Jensen, Ole Mejlhede

    2008-01-01

    This paper describes a new technology for air-entrainment of concrete. The technology is based on the addition of dry superabsorbent polymers (SAP) to the concrete. A large amount of small internal water reservoirs are formed during mixing when SAP absorbs water and swells. The internal water......-entrainment include stability of the air void system and improved control of both the amount of added air and the air void size. The new technology based on SAP has been tested in freeze-thaw experiments, where the amount of surface scaling was measured. The results clearly show that SAP is beneficial for frost...... reservoirs are distributed throughout the concrete. During the hydration process the cement paste imbibes water from the water-filled SAP voids. Thereby the water-filled SAP voids turn into partly air-filled voids. The advantages of the SAP-based technology compared to traditional chemical air...

  14. Properties of Waste from Coal Gasification in Entrained Flow Reactors in the Aspect of Their Use in Mining Technology / Właściwości odpadów ze zgazowania węgla w reaktorach dyspersyjnych w aspekcie ich wykorzystania w technologiach górniczych

    Science.gov (United States)

    Pomykała, Radosław

    2013-06-01

    Most of the coal gasification plants based of one of the three main types of reactors: fixed bed, fluidized bed or entrained flow. In recent years, the last ones, which works as "slagging" reactors (due to the form of generated waste), are very popular among commercial installations. The article discusses the characteristics of the waste from coal gasification in entrained flow reactors, obtained from three foreign installations. The studies was conducted in terms of the possibilities of use these wastes in mining technologies, characteristic for Polish underground coal mines. The results were compared with the requirements of Polish Standards for the materials used in hydraulic backfill as well as suspension technology: solidification backfill and mixtures for gob caulking. Większość przemysłowych instalacji zgazowania węgla pracuje w oparciu o jeden z trzech głównych typów reaktorów: ze złożem stałym, dyspersyjny lub fluidalny. W zależności od rodzaju reaktora oraz szczegółowych rozwiązań instalacji, powstające uboczne produkty zgazowania mogą mieć różną postać. Zależy ona w dużej mierze od stosunku temperatury pracy reaktora do temperatury topnienia części mineralnych zawartych w paliwie, czyli do temperatury mięknienia i topnienia popiołu. W ostatnich latach bardzo dużą popularność wśród instalacji komercyjnych zdobywają reaktory dyspersyjne "żużlujące". W takich instalacjach żużel jest wychwytywany i studzony po wypłynięciu z reaktora. W niektórych przypadkach oprócz żużla powstaje jeszcze popiół lotny, wychwytywany w systemach odprowadzania spalin. Może być on pozyskiwany oddzielnie lub też zawracany do komory reaktora, gdzie ulega stopieniu. Wszystkie z analizowanych odpadów - trzy żużle oraz popiół pochodzą właśnie z tego typu instalacji. Tylko z jednej z nich pozyskano zarówno żużel jak i popiół, z pozostałych dwóch jedynie żużel. Odpady te powstały, jako uboczny produkt zgazowania w

  15. Large Eddy Simulation of Heat Entrainment Under Arctic Sea Ice

    Science.gov (United States)

    Ramudu, Eshwan; Gelderloos, Renske; Yang, Di; Meneveau, Charles; Gnanadesikan, Anand

    2018-01-01

    Arctic sea ice has declined rapidly in recent decades. The faster than projected retreat suggests that free-running large-scale climate models may not be accurately representing some key processes. The small-scale turbulent entrainment of heat from the mixed layer could be one such process. To better understand this mechanism, we model the Arctic Ocean's Canada Basin, which is characterized by a perennial anomalously warm Pacific Summer Water (PSW) layer residing at the base of the mixed layer and a summertime Near-Surface Temperature Maximum (NSTM) within the mixed layer trapping heat from solar radiation. We use large eddy simulation (LES) to investigate heat entrainment for different ice-drift velocities and different initial temperature profiles. The value of LES is that the resolved turbulent fluxes are greater than the subgrid-scale fluxes for most of our parameter space. The results show that the presence of the NSTM enhances heat entrainment from the mixed layer. Additionally there is no PSW heat entrained under the parameter space considered. We propose a scaling law for the ocean-to-ice heat flux which depends on the initial temperature anomaly in the NSTM layer and the ice-drift velocity. A case study of "The Great Arctic Cyclone of 2012" gives a turbulent heat flux from the mixed layer that is approximately 70% of the total ocean-to-ice heat flux estimated from the PIOMAS model often used for short-term predictions. Present results highlight the need for large-scale climate models to account for the NSTM layer.

  16. Neural entrainment to the rhythmic structure of music.

    Science.gov (United States)

    Tierney, Adam; Kraus, Nina

    2015-02-01

    The neural resonance theory of musical meter explains musical beat tracking as the result of entrainment of neural oscillations to the beat frequency and its higher harmonics. This theory has gained empirical support from experiments using simple, abstract stimuli. However, to date there has been no empirical evidence for a role of neural entrainment in the perception of the beat of ecologically valid music. Here we presented participants with a single pop song with a superimposed bassoon sound. This stimulus was either lined up with the beat of the music or shifted away from the beat by 25% of the average interbeat interval. Both conditions elicited a neural response at the beat frequency. However, although the on-the-beat condition elicited a clear response at the first harmonic of the beat, this frequency was absent in the neural response to the off-the-beat condition. These results support a role for neural entrainment in tracking the metrical structure of real music and show that neural meter tracking can be disrupted by the presentation of contradictory rhythmic cues.

  17. Slowly rotating general relativistic superfluid neutron stars with relativistic entrainment

    International Nuclear Information System (INIS)

    Comer, G.L.

    2004-01-01

    Neutron stars that are cold enough should have two or more superfluids or supercondutors in their inner crusts and cores. The implication of superfluidity or superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An important consequence of the quasiparticle nature of each condensate is the so-called entrainment effect; i.e., the momentum of a condensate is a linear combination of its own current and those of the other condensates. We present here the first fully relativistic modeling of slowly rotating superfluid neutron stars with entrainment that is accurate to the second-order in the rotation rates. The stars consist of superfluid neutrons, superconducting protons, and a highly degenerate, relativistic gas of electrons. We use a relativistic σ-ω mean field model for the equation of state of the matter and the entrainment. We determine the effect of a relative rotation between the neutrons and protons on a star's total mass, shape, and Kepler, mass-shedding limit

  18. Freeze-Thaw Durability of Air-Entrained Concrete

    Directory of Open Access Journals (Sweden)

    Huai-Shuai Shang

    2013-01-01

    Full Text Available One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles. The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss and internal crack growth (characterized by the loss of dynamic modulus of elasticity. The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

  19. Freeze-thaw durability of air-entrained concrete.

    Science.gov (United States)

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

  20. Presence of strong harmonics during visual entrainment: a magnetoencephalography study.

    Science.gov (United States)

    Heinrichs-Graham, Elizabeth; Wilson, Tony W

    2012-09-01

    Visual neurons are known to synchronize their firing with stimuli that flicker at a constant rate (e.g. 12Hz). These so-called visual steady-state responses (VSSR) are a well-studied phenomenon, yet the underlying mechanisms are widely disagreed upon. Furthermore, there is limited evidence that visual neurons may simultaneously synchronize at harmonics of the stimulation frequency. We utilized magnetoencephalography (MEG) to examine synchronization at harmonics of the visual stimulation frequency (18Hz). MEG data were analyzed for event-related-synchronization (ERS) at the fundamental frequency, 36, 54, and 72Hz. We found strong ERS in all bands. Only 31% of participants showed maximum entrainment at the fundamental; others showed stronger entrainment at either 36 or 54Hz. The cortical foci of these responses indicated that the harmonics involved cortices that were partially distinct from the fundamental. These findings suggest that spatially-overlapping subpopulations of neurons are simultaneously entrained at different harmonics of the stimulus frequency. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. The effect of flow direction and magnitude on CHF for low pressure water in thin rectangular channels

    International Nuclear Information System (INIS)

    Mishima, K.; Nishihara, H.

    1985-01-01

    Critical heat flow (CHF) at low flow condition can become important in an MTR-type research reactor under a number of accident conditions. Regardless of the initial stages of these accidents, a condition which is basically the decay heat removal by natural convention boiling can develop. Under such conditions, burnout may occur even at a very low heat flow. In view of this, the CHF at low-flow-rate and low-pressure conditions has been studied for water flowing in thin rectangular channels. Experiments were carried out with two types of rectangular test sections, namely, the one heated from one wide side and the other heated from two opposite sides. In order to observe the effects of gravity, CHF was measured both in upflow and downflow. The CHF at complete bottom blockage was also studied. The results indicate that burnout can occur at a much lower heat flux than pool-boiling CHF or than predicted by the conventional correlations. There was observed a minimum CHF at complete bottom blockage and at very low downflow. The low CHF at very low downflow appears to be due to the stagnation of the bubble in the heated section. This fact indicates that special care should be taken in analyzing the boiling phenomenon which occurs when the coolant flow is very low in a low pressure system. (author)

  2. Intraflow width variations in Martian and terrestrial lava flows

    Science.gov (United States)

    Peitersen, Matthew N.; Crown, David A.

    1997-03-01

    Flow morphology is used to interpret emplacement processes for lava flows on Earth and Mars. Accurate measurements of flow geometry are essential, particularly for planetary flows where neither compositional sampling nor direct observations of active flows may be possible. Width behavior may indicate a flow's response to topography, its emplacement regime, and its physical properties. Variations in width with downflow distance from the vent may therefore provide critical clues to flow emplacement processes. Flow width is also one of the few characteristics that can be readily measured from planetary mission data with accuracy. Recent analyses of individual flows at two terrestrial and four Martian sites show that widths within an individual flow vary by up to an order of magnitude. Width is generally thought to be correlated to topography; however, recent studies show that this relationship is neither straightforward nor easily quantifiable.

  3. Study of air entrainment in high pressure spray: optics diagnostics and application to the Diesel injection; Etude de l'entrainement d'air dans un spray haute pression: diagnostics optiques et application a l'injection diesel

    Energy Technology Data Exchange (ETDEWEB)

    Arbeau, A.

    2004-12-15

    The actual development of the engine must reply to a will of fuel consumption reduction and to norms more and more strict concerning the pollutant emissions. Although the Diesel engines are efficient, the NO{sub x} and particle emissions mainly come from the existence of wealthy fuel zone preventing an optimal combustion. Therefore, the air / fuel mixing preparation, highly controlled by the air entrainment in spray, is essential. In this context, we have developed metrological tools in order to analyse the air entrainment mechanism in a dense spray. The Particle Image Velocimetry (PIV) technique is first applied to a conical spray with an injection pressure less than 100 bars to study the air entrainment in spray. A transfer of the methodologies allows then the characterisation and the understanding of the air entrainment mechanism in high pressure full spray (injection pressure less than 1600 bars) type Diesel one. The influence of injection parameters (injection pressure and back pressure) on the mixing rate is studied. The increase of the injection pressure from 800 to 1600 bars implies an increase of the mixing rate of 60 %. Moreover, the thermodynamic conditions of the ambient air, simulated by the chamber back pressure, widely favours the mixing rate. Actually, this latter increases of 350 % when the chamber back pressure varies from 1 to 7 bars. The experimental results do not follow classical laws of air entrainment in one-phase flow jet with variable density, but are in good agreement with an integral model for air entrainment in an axisymmetric full spray. Finally, the Fluorescence Particle Image Velocimetry (FPIV) is introduced in order to extend the PIV application field in dense two-phase flows. (author)

  4. On the pollutant removal, dispersion, and entrainment over two-dimensional idealized street canyons

    Science.gov (United States)

    Liu, Chun-Ho; Wong, Colman C. C.

    2014-01-01

    Pollutant dispersion over urban areas is not that well understood, in particular at the street canyon scale. This study is therefore conceived to examine how urban morphology modifies the pollutant removal, dispersion, and entrainment over urban areas. An idealized computational domain consisting of 12 two-dimensional (2D) identical street canyons of unity aspect ratio is employed. The large-eddy simulation (LES) is used to calculate the turbulent flows and pollutant transport in the urban boundary layer (UBL). An area source of uniform pollutant concentration is applied on the ground of the first street canyon. A close examination on the roof-level turbulence reveals patches of low-speed air masses in the streamwise flows and narrow high-speed downdrafts in the shear layer. Different from the flows over a smooth surface, the turbulence intensities are peaked near the top of the building roughness. The pollutant is rather uniformly distributed inside a street canyon but disperses quickly in the UBL over the buildings. Partitioning the vertical pollutant flux into its mean and turbulent components demystifies that the pollutant removal is mainly governed by turbulence. Whereas, mean wind carries pollutant into and out of a street canyon simultaneously. In addition to wind speed promotion, turbulent mixing is thus required to dilute the ground-level pollutants, which are then removed from the street canyon to the UBL. Atmospheric flows slow down rapidly after the leeward buildings, leading to updrafts carrying pollutants away from the street canyons (the basic pollutant removal mechanism).

  5. Doing Duo – a Case Study of Entrainment in William Forsythe’s Choreography Duo

    Directory of Open Access Journals (Sweden)

    Elizabeth eWaterhouse

    2014-10-01

    Full Text Available Entrainment theory focuses on processes in which interacting (i.e. coupled rhythmic systems stabilize, producing synchronization in the ideal sense, and forms of phase related rhythmic coordination in complex cases. In human action, entrainment involves spatiotemporal and social aspects, characterizing the meaningful activities of music, dance, and communication. How can the phenomenon of human entrainment be meaningfully studied in complex situations such as dance? We present an in-progress case study of entrainment in William Forsythe's choreography Duo, a duet in which coordinated rhythmic activity is achieved without an external musical beat and without touch-based interaction. Using concepts of entrainment from different disciplines as well as insight from Duo performer Riley Watts, we question definitions of entrainment in the context of dance. The functions of chorusing, turn-taking, complementary action, cues and alignments are discussed and linked to supporting annotated video material. While Duo challenges the definition of entrainment in dance as coordinated response to an external musical or rhythmic signal, it supports the definition of entrainment as coordinated interplay of motion and sound production by active agents (i.e., dancers in the field. Agreeing that human entrainment should be studied on multiple levels, we suggest that entrainment between the dancers in Duo is elastic in time and a propose how to test this hypothesis empirically. We do not claim that our proposed model of elasticity is applicable to all forms of human entrainment nor to all to examples of entrainment in dance. Rather, we suggest studying higher order phase correction (the stabilizing tendency of entrainment as a potential aspect to be incorporated into other models.

  6. The effects of mass flows on the dissipation of Alfvacute en waves in the upper layers of the solar atmosphere

    International Nuclear Information System (INIS)

    Ryutova, M.P.; Habbal, S.R.

    1995-01-01

    The influence of parallel plasma flows on the propagation of shear Alfvacute en waves along magnetic structures is considered. It is shown that even in a simple case of regular mass flows directed along the magnetic field, their presence considerably modifies the dissipation of shear Alfvacute en waves, affecting both the magnitude and the height of maximum dissipation. The strongest effect occurs in the case of downflows when the flow velocity at a certain height becomes equal to the Alfvacute en velocity. Near that point, the wave comes to extinction and gives off its energy completely. The axial extent of the absorption region is evaluated. This effect can be directly associated with observed high-velocity downflows in the transition region, and, in particular, can serve as a qualitative explanation for the high variability of the emission observed near 10 5 K. In the presence of upward mass flows and moderate downflows, the dissipation of phase-mixed Alfvacute en waves is accompanied by the radial redistribution of the energy input across the magnetic structure, thus creating a mosaic pattern in the emitting regions. The flow velocities are assumed to be below the thresholds which correspond to the onset of hydrodynamic and dissipative instabilities. copyright 1995 The American Astronomical Society

  7. Spontaneous Entrainment of Running Cadence to Music Tempo.

    Science.gov (United States)

    Van Dyck, Edith; Moens, Bart; Buhmann, Jeska; Demey, Michiel; Coorevits, Esther; Dalla Bella, Simone; Leman, Marc

    Since accumulating evidence suggests that step rate is strongly associated with running-related injuries, it is important for runners to exercise at an appropriate running cadence. As music tempo has been shown to be capable of impacting exercise performance of repetitive endurance activities, it might also serve as a means to (re)shape running cadence. The aim of this study was to validate the impact of music tempo on running cadence. Sixteen recreational runners ran four laps of 200 m (i.e. 800 m in total); this task was repeated 11 times with a short break in between each four-lap sequence. During the first lap of a sequence, participants ran at a self-paced tempo without musical accompaniment. Running cadence of the first lap was registered, and during the second lap, music with a tempo matching the assessed cadence was played. In the final two laps, the music tempo was either increased/decreased by 3.00, 2.50, 2.00, 1.50, or 1.00 % or was kept stable. This range was chosen since the aim of this study was to test spontaneous entrainment (an average person can distinguish tempo variations of about 4 %). Each participant performed all conditions. Imperceptible shifts in musical tempi in proportion to the runner's self-paced running tempo significantly influenced running cadence ( p  tempo conditions and adaptation in running cadence ( p  effect of condition on the level of entrainment was revealed ( p  effects of music tempo on running cadence can only be obtained up to a certain level of tempo modification. Finally, significantly higher levels of tempo entrainment were found for female participants compared to their male counterparts ( p  music tempo could serve as an unprompted means to impact running cadence. As increases in step rate may prove beneficial in the prevention and treatment of common running-related injuries, this finding could be especially relevant for treatment purposes, such as exercise prescription and gait retraining. Music tempo

  8. The effects of chronic marijuana use on circadian entrainment.

    Science.gov (United States)

    Whitehurst, Lauren N; Fogler, Kethera; Hall, Kate; Hartmann, Matthew; Dyche, Jeff

    2015-05-01

    Animal literature suggests a connection between marijuana use and altered circadian rhythms. However, the effect has not yet been demonstrated in humans. The present study examined the effect of chronic marijuana use on human circadian function. Participants consisted of current users who reported smoking marijuana daily for at least a year and non-marijuana user controls. Participants took a neurocognitive assessment, wore actigraphs and maintained sleep diaries for three weeks. While no significant cognitive changes were found between groups, data revealed that chronic marijuana use may act as an additional zeitgeber and lead to increased entrainment in human users.

  9. Hydrodynamics of annular-dispersed flow

    International Nuclear Information System (INIS)

    Ishii, M.; Kataoka, I.

    1982-01-01

    The interfacial drag, droplet entrainment, and droplet size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The drag correlations for multiple fluid particle systems have been developed from a similarity hypothesis based on the mixture viscosity model. The results show that the drag coefficient depends on the particle Reynolds number and droplet concentration. The onset on droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet size distribution have been obtained from a simple model in collaboration with a large number of data

  10. Modeling variable density turbulence in the wake of an air-entraining transom stern

    Science.gov (United States)

    Hendrickson, Kelli; Yue, Dick

    2015-11-01

    This work presents a priori testing of closure models for the incompressible highly-variable density turbulent (IHVDT) flows in the near wake region of a transom stern. This three-dimensional flow is comprised of convergent corner waves that originate from the body and collide on the ship center plane forming the ``rooster tail'' that then widens to form the divergent wave train. These violent free-surface flows and breaking waves are characterized by significant turbulent mass flux (TMF) at Atwood number At = (ρ2 -ρ1) / (ρ2 +ρ1) ~ 1 for which there is little guidance in turbulence closure modeling for the momentum and scalar transport along the wake. To whit, this work utilizes high-resolution simulations of the near wake of a canonical three-dimensional transom stern using conservative Volume-of-Fluid (cVOF), implicit Large Eddy Simulation (iLES), and Boundary Data Immersion Method (BDIM) to capture the turbulence and large scale air entrainment. Analysis of the simulation results across and along the wake for the TMF budget and turbulent anisotropy provide the physical basis of the development of multiphase turbulence closure models. Performance of isotropic and anisotropic turbulent mass flux closure models will be presented. Sponsored by the Office of Naval Research.

  11. Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation.

    Science.gov (United States)

    Sameiro-Barbosa, Catia M; Geiser, Eveline

    2016-01-01

    The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system.

  12. Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation

    Science.gov (United States)

    Sameiro-Barbosa, Catia M.; Geiser, Eveline

    2016-01-01

    The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system. PMID:27559306

  13. Research on the pyrolysis of hardwood in an entrained bed process development unit

    Energy Technology Data Exchange (ETDEWEB)

    Kovac, R.J.; Gorton, C.W.; Knight, J.A.; Newman, C.J.; O' Neil, D.J. (Georgia Inst. of Tech., Atlanta, GA (United States). Research Inst.)

    1991-08-01

    An atmospheric flash pyrolysis process, the Georgia Tech Entrained Flow Pyrolysis Process, for the production of liquid biofuels from oak hardwood is described. The development of the process began with bench-scale studies and a conceptual design in the 1978--1981 timeframe. Its development and successful demonstration through research on the pyrolysis of hardwood in an entrained bed process development unit (PDU), in the period of 1982--1989, is presented. Oil yields (dry basis) up to 60% were achieved in the 1.5 ton-per-day PDU, far exceeding the initial target/forecast of 40% oil yields. Experimental data, based on over forty runs under steady-state conditions, supported by material and energy balances of near-100% closures, have been used to establish a process model which indicates that oil yields well in excess of 60% (dry basis) can be achieved in a commercial reactor. Experimental results demonstrate a gross product thermal efficiency of 94% and a net product thermal efficiency of 72% or more; the highest values yet achieved with a large-scale biomass liquefaction process. A conceptual manufacturing process and an economic analysis for liquid biofuel production at 60% oil yield from a 200-TPD commercial plant is reported. The plant appears to be profitable at contemporary fuel costs of $21/barrel oil-equivalent. Total capital investment is estimated at under $2.5 million. A rate-of-return on investment of 39.4% and a pay-out period of 2.1 years has been estimated. The manufacturing cost of the combustible pyrolysis oil is $2.70 per gigajoule. 20 figs., 87 tabs.

  14. Rayleigh-Taylor Type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-arcade Downflows in the Sun

    Science.gov (United States)

    Guo, L.-J.; Huang, Y.-M.; Bhattacharjee, A.; Innes, D. E.

    2014-12-01

    Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features observed in active region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright upward growing spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for more than a decade, the mechanism of the formation of SADs remains an open issue. Using three-dimensional resistive magnetohydrodynamic simulations, we demonstrate that Rayleigh-Taylor-type instabilities develop in the downstream region of a reconnecting current sheet. The instabilities result in the formation of low-density coherent structures that resemble SADs, and high-density structures that appear to be spike-like. Comparison between the simulation results and observations suggests that Rayleigh-Taylor-type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs.

  15. Entrainment and high-density three-dimensional mapping in right atrial macroreentry provide critical complementary information: Entrainment may unmask "visual reentry" as passive.

    Science.gov (United States)

    Pathik, Bhupesh; Lee, Geoffrey; Nalliah, Chrishan; Joseph, Stephen; Morton, Joseph B; Sparks, Paul B; Sanders, Prashanthan; Kistler, Peter M; Kalman, Jonathan M

    2017-10-01

    With the recent advent of high-density (HD) 3-dimensional (3D) mapping, the utility of entrainment is uncertain. However, the limitations of visual representation and interpretation of these high-resolution 3D maps are unclear. The purpose of this study was to determine the strengths and limitations of both HD 3D mapping and entrainment mapping during mapping of right atrial macroreentry. Fifteen patients were studied. The number and type of circuits accounting for ≥90% of the tachycardia cycle length using HD 3D mapping were verified using systematic entrainment mapping. Entrainment sites with an unexpectedly long postpacing interval despite proximity to the active circuit were evaluated. Based on HD 3D mapping, 27 circuits were observed: 12 peritricuspid, 2 upper loop reentry, 10 lower loop reentry, and 3 lateral wall circuits. With entrainment, 17 of the 27 circuits were active: all 12 peritricuspid and 2 upper loop reentry. However, lower loop reentry was confirmed in only 3 of 10, and none of the 3 lateral wall circuits were present. Mean percentage of tachycardia cycle length covered by active circuits was 98% ± 1% vs 97% ± 2% for passive circuits (P = .09). None of the 345 entrainment runs terminated tachycardia or changed tachycardia mechanism. In 8 of 15 patients, 13 examples of unexpectedly long postpacing interval were observed at entrainment sites located distal to localized zones of slow conduction seen on HD 3D mapping. Using HD 3D mapping, "visual reentry" may be due to passive circuitous propagation rather than a critical reentrant circuit. HD 3D mapping provides new insights into regional conduction and helps explain unusual entrainment phenomena. Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  16. Quantification of the effect of oil layer thickness on entrainment of surface oil

    NARCIS (Netherlands)

    Klaas Dijkstra; Albertinka J. Murk; Marieke Zeinstra-Helfrich; Wierd Koops

    2015-01-01

    This study quantifies the effect of oil layer thickness on entrainment and dispersion of oil into seawater, using a plunging jet with a camera system. In contrast to what is generally assumed, we revealed that for the low viscosity “surrogate MC252 oil” we used, entrainment rate is directly

  17. Accuracy of circadian entrainment under fluctuating light conditions : Contributions of phase and period responses

    NARCIS (Netherlands)

    Beersma, DGM; Daan, S; Hut, RA

    The accuracy with which a circadian pacemaker can entrain to an environmental 24-h zeitgeber signal depends on (a) characteristics of the entraining signal and (b) response characteristics and intrinsic stability of the pacemaker itself. Position of the sun, weather conditions, shades, and

  18. Nonphotic entrainment in a diurnal mammal, the European ground squirrel (Spermophilus citellus)

    NARCIS (Netherlands)

    Hut, Roelof A.; Mrosovsky, N.; Daan, Serge

    1999-01-01

    Entrainment by nonphotic, activity-inducing stimuli has been investigated in detail in nocturnal rodents, but little is known about nonphotic entrainment in diurnal animals. Comparative studies would offer the opportunity to distinguish between two possibilities. (1) If nonphotic phase shifts depend

  19. A review of the interference of carbon containing fly ash with air entrainment in concrete

    DEFF Research Database (Denmark)

    Pedersen, Kim Hougaard; Jensen, Anker Degn; Skjøth-Rasmussen, Martin Skov

    2008-01-01

    may interfere with air entraining admixtures (AEAs) added to enhance air entrainment in concrete in order to increase its workability and resistance toward freezing and thawing conditions. The problem has increased with implementation of low-NOx combustion technologies. This review presents the past...

  20. Broadening of cloud droplet spectra through turbulent entrainment and eddy hopping

    Science.gov (United States)

    Abade, Gustavo; Grabowski, Wojciech; Pawlowska, Hanna

    2017-11-01

    This work discusses the effect of cloud turbulence and turbulent entrainment on the evolution of the cloud droplet-size spectrum. We simulate an ensemble of idealized turbulent cloud parcels that are subject to entrainment events, modeled as a random Poisson process. Entrainment events, subsequent turbulent mixing inside the parcel, supersaturation fluctuations, and the resulting stochastic droplet growth by condensation are simulated using a Monte Carlo scheme. Quantities characterizing the turbulence intensity, entrainment rate and the mean fraction of environmental air entrained in an event are specified as external parameters. Cloud microphysics is described by applying Lagrangian particles, the so-called superdroplets. They are either unactivated cloud condensation nuclei (CCN) or cloud droplets that form from activated CCN. The model accounts for the transport of environmental CCN into the cloud by the entraining eddies at the cloud edge. Turbulent mixing of the entrained dry air with cloudy air is described using a linear model. We show that turbulence plays an important role in aiding entrained CCN to activate, providing a source of small cloud droplets and thus broadening the droplet size distribution. Further simulation results will be reported at the meeting.

  1. The role of high-level processes for oscillatory phase entrainment to speech sound

    Directory of Open Access Journals (Sweden)

    Benedikt eZoefel

    2015-12-01

    Full Text Available Constantly bombarded with input, the brain has the need to filter out relevant information while ignoring the irrelevant rest. A powerful tool may be represented by neural oscillations which entrain their high-excitability phase to important input while their low-excitability phase attenuates irrelevant information. Indeed, the alignment between brain oscillations and speech improves intelligibility and helps dissociating speakers during a cocktail party. Although well-investigated, the contribution of low- and high-level processes to phase entrainment to speech sound has only recently begun to be understood. Here, we review those findings, and concentrate on three main results: (1 Phase entrainment to speech sound is modulated by attention or predictions, likely supported by top-down signals and indicating higher-level processes involved in the brain’s adjustment to speech. (2 As phase entrainment to speech can be observed without systematic fluctuations in sound amplitude or spectral content, it does not only reflect a passive steady-state ringing of the cochlea, but entails a higher-level process. (3 The role of intelligibility for phase entrainment is debated. Recent results suggest that intelligibility modulates the behavioral consequences of entrainment, rather than directly affecting the strength of entrainment in auditory regions. We conclude that phase entrainment to speech reflects a sophisticated mechanism: Several high-level processes interact to optimally align neural oscillations with predicted events of high relevance, even when they are hidden in a continuous stream of background noise.

  2. Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment

    Science.gov (United States)

    Narasimha, Roddam; Diwan, Sourabh Suhas; Duvvuri, Subrahmanyam; Sreenivas, K. R.; Bhat, G. S.

    2011-01-01

    Clouds are the largest source of uncertainty in climate science, and remain a weak link in modeling tropical circulation. A major challenge is to establish connections between particulate microphysics and macroscale turbulent dynamics in cumulus clouds. Here we address the issue from the latter standpoint. First we show how to create bench-scale flows that reproduce a variety of cumulus-cloud forms (including two genera and three species), and track complete cloud life cycles—e.g., from a “cauliflower” congestus to a dissipating fractus. The flow model used is a transient plume with volumetric diabatic heating scaled dynamically to simulate latent-heat release from phase changes in clouds. Laser-based diagnostics of steady plumes reveal Riehl–Malkus type protected cores. They also show that, unlike the constancy implied by early self-similar plume models, the diabatic heating raises the Taylor entrainment coefficient just above cloud base, depressing it at higher levels. This behavior is consistent with cloud-dilution rates found in recent numerical simulations of steady deep convection, and with aircraft-based observations of homogeneous mixing in clouds. In-cloud diabatic heating thus emerges as the key driver in cloud development, and could well provide a major link between microphysics and cloud-scale dynamics. PMID:21918112

  3. Entrainment in the inner crust of a neutron star

    International Nuclear Information System (INIS)

    Chamel, N.

    2004-01-01

    The inner crust of a neutron star, which is composed of a solid Coulomb lattice of nuclei immersed in a neutron super-fluid, is studied from both a macroscopic and a microscopic level. In the first part, we develop a non-relativistic but 4-dimensionally covariant formulation of the hydrodynamics of a perfect fluid mixture based on a variational principle. This formalism is applied to the description of neutron star crust as 2-fluid model, a neutron super-fluid and a plasma of nuclei and electrons coupled via non dissipative entrainment effects, whose microscopic evaluation is studied in a second part. Applying mean field methods beyond the Wigner-Seitz approximation, the Bragg scattering of dripped neutrons upon crustal nuclei lead to a 'mesoscopic' effective neutron mass, which unlike the 'microscopic' effective mass, takes very large values compared to the bare mass in the middle layers of the crust. (author)

  4. Impingement and entrainment: an updated annotated bibliography. Final report

    International Nuclear Information System (INIS)

    Yost, F.E.; Uziel, M.S.

    1981-05-01

    Presented as an annotated bibliography are 1343 references dealing with entrainment and impingement effects on aquatic organisms passing through the cooling systems of thermal power plants. The references were obtained from open literature and from environmental reports and impact statements prepared by or for the electric utility industry. Two earlier bibliographies contain literature from 1950 through 1976. This update contains additional literature acquired since 1976. Topics covered are site-specific field studies at facilities located on lakes, reservoirs, rivers, or estuaries. The studies include special engineering studies, laboratory studies, studies of biological effects, reviews and methodologies, and studies of the mitigation of effects. References are arranged alphabetically by author, and indexes are provided to personal and corporate authors, and to facility, waterbody, and taxonomic names

  5. Out-of-synchrony speech entrainment in developmental dyslexia.

    Science.gov (United States)

    Molinaro, Nicola; Lizarazu, Mikel; Lallier, Marie; Bourguignon, Mathieu; Carreiras, Manuel

    2016-08-01

    Developmental dyslexia is a reading disorder often characterized by reduced awareness of speech units. Whether the neural source of this phonological disorder in dyslexic readers results from the malfunctioning of the primary auditory system or damaged feedback communication between higher-order phonological regions (i.e., left inferior frontal regions) and the auditory cortex is still under dispute. Here we recorded magnetoencephalographic (MEG) signals from 20 dyslexic readers and 20 age-matched controls while they were listening to ∼10-s-long spoken sentences. Compared to controls, dyslexic readers had (1) an impaired neural entrainment to speech in the delta band (0.5-1 Hz); (2) a reduced delta synchronization in both the right auditory cortex and the left inferior frontal gyrus; and (3) an impaired feedforward functional coupling between neural oscillations in the right auditory cortex and the left inferior frontal regions. This shows that during speech listening, individuals with developmental dyslexia present reduced neural synchrony to low-frequency speech oscillations in primary auditory regions that hinders higher-order speech processing steps. The present findings, thus, strengthen proposals assuming that improper low-frequency acoustic entrainment affects speech sampling. This low speech-brain synchronization has the strong potential to cause severe consequences for both phonological and reading skills. Interestingly, the reduced speech-brain synchronization in dyslexic readers compared to normal readers (and its higher-order consequences across the speech processing network) appears preserved through the development from childhood to adulthood. Thus, the evaluation of speech-brain synchronization could possibly serve as a diagnostic tool for early detection of children at risk of dyslexia. Hum Brain Mapp 37:2767-2783, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  6. The performative pleasure of imprecision: a diachronic study of entrainment in music performance

    Directory of Open Access Journals (Sweden)

    Andrew eGeeves

    2014-10-01

    Full Text Available This study focuses in on a moment of live performance in which the entrainment amongst a musical quartet is threatened. Entrainment is asymmetric in so far as there is an ensemble leader who improvises and expands the structure of a last chorus of a piece of music beyond the limits tacitly negotiated during prior rehearsals and performances. Despite the risk of entrainment being disturbed and performance interrupted, the other three musicians in the quartet follow the leading performer and smoothly transition into unprecedented performance territory. We use this moment of live performance to work back through the fieldwork data, building a diachronic study of the development and bases of entrainment in live music performance. We introduce the concept of entrainment and profile previous theory and research relevant to entrainment in music performance. After outlining our methodology, we trace the evolution of the structure of the piece of music from first rehearsal to final performance. Using video clip analysis, interviews and field notes we consider how entrainment shaped and was shaped by the moment of performance in focus. The sense of trust between quartet musicians is established through entrainment processes, is consolidated via smooth adaptation to the threats of disruption. Nonverbal communicative exchanges, via eye contact, gesture and spatial proximity, sustain entrainment through phase shifts occurring swiftly and on the fly in performance contexts. These exchanges permit smooth adaptation promoting trust. This frees the quartet members to play with the potential disturbance of equilibrium inherent in entrained relationships and to play with this tension in an improvisatory way that enhances audience engagement and the live quality of performance.

  7. Measurement of two-phase flow at the core upper plenum interface under simulated reflood conditions

    International Nuclear Information System (INIS)

    Thomas, D.G.; Combs, S.K.; Bagwell, M.E.

    1980-01-01

    Objectives of the Instrument Development Loop program were to simulate flows at the core/upper plenum interface during the reflood phase of a LOCA and to develop instruments for measuring mass-flows at this interface. A tie plate drag body was developed and tested successfully, and the data obtained were shown to be equivalent to pressure drops. The tie-plate drag body gave useful measurements in pure downflow, and the drag/turbine combination correlates with mass flow for high upflow

  8. Reducing the Entrainment of Gangue Fines in Low Grade Microcrystalline Graphite Ore Flotation Using Multi-Stage Grinding-Flotation Process

    Directory of Open Access Journals (Sweden)

    Xiaoqing Weng

    2017-03-01

    Full Text Available A suitable grinding fineness and flow-sheet could potentially reduce the mechanical entrainment of gangue minerals in the flotation process of microcrystalline graphite. In this study, the suitable grinding fineness of a commercial graphite ore was estimated by mineralogy analysis and laboratory grind-flotation tests. The target grind size of this ore should be 92% passing 74 μm based on the mineralogical evaluation and the flotation performance. A comparison of a single-stage and a three-stage grinding circuit was conducted. Experimental results demonstrated that the three-stage grinding circuit could effectively improve the separation effect, which was attributed to the reduction of slimes. In the end, a more desirable beneficiation result was obtained with the application of three-stage grinding-flotation process by minimizing gangue entrainment.

  9. Neurobiological foundations of neurologic music therapy: rhythmic entrainment and the motor system.

    Science.gov (United States)

    Thaut, Michael H; McIntosh, Gerald C; Hoemberg, Volker

    2014-01-01

    Entrainment is defined by a temporal locking process in which one system's motion or signal frequency entrains the frequency of another system. This process is a universal phenomenon that can be observed in physical (e.g., pendulum clocks) and biological systems (e.g., fire flies). However, entrainment can also be observed between human sensory and motor systems. The function of rhythmic entrainment in rehabilitative training and learning was established for the first time by Thaut and colleagues in several research studies in the early 1990s. It was shown that the inherent periodicity of auditory rhythmic patterns could entrain movement patterns in patients with movement disorders (see for a review: Thaut et al., 1999). Physiological, kinematic, and behavioral movement analysis showed very quickly that entrainment cues not only changed the timing of movement but also improved spatial and force parameters. Mathematical models have shown that anticipatory rhythmic templates as critical time constraints can result in the complete specification of the dynamics of a movement over the entire movement cycle, thereby optimizing motor planning and execution. Furthermore, temporal rhythmic entrainment has been successfully extended into applications in cognitive rehabilitation and speech and language rehabilitation, and thus become one of the major neurological mechanisms linking music and rhythm to brain rehabilitation. These findings provided a scientific basis for the development of neurologic music therapy.

  10. Estimates of entrainment mortality for striped bass and other fish species inhabiting the Hudson River estuary

    International Nuclear Information System (INIS)

    Boreman, J.; Goodyear, C.P.

    1988-01-01

    An empirically derived age-, time-, and space-variant equation was used to estimate entrainment mortality at power plants for seven fish species inhabiting the Hudson River estuary. Entrainment mortality is expressed as a conditional rate, which is the fractional reduction in year-class strength due to entrainment if other sources of mortality are density-independent. Estimates of the conditional entrainment mortality, based on historical and projected once-through cooling operation of five power plants, were 11-22% for striped bass, 11-17% for white perch, 5-7% for Atlantic tomcod, 14-21% for American shad, 4-11% for river herring (alewife and blueback herring combined), and 35-79% for bay anchovy. Closed-cycle cooling (natural-draft cooling towers) at three of the power plants (Indian Point, Bowline Point, and Roseton) would reduce entrainment mortality of striped bass by 50-80%, of white perch by 75-80%, of Atlantic tocod by 65-70%, of American shad by 80%, of river herring by 30-90%, and of bay anchovy by 45-80%. The life stages most vulnerable to entrainment mortality were post-yolk-sac larva and entrainable size juvenile. 18 refs., 7 tabs

  11. Neurobiological foundations of neurologic music therapy: rhythmic entrainment and the motor system

    Science.gov (United States)

    Thaut, Michael H.; McIntosh, Gerald C.; Hoemberg, Volker

    2015-01-01

    Entrainment is defined by a temporal locking process in which one system’s motion or signal frequency entrains the frequency of another system. This process is a universal phenomenon that can be observed in physical (e.g., pendulum clocks) and biological systems (e.g., fire flies). However, entrainment can also be observed between human sensory and motor systems. The function of rhythmic entrainment in rehabilitative training and learning was established for the first time by Thaut and colleagues in several research studies in the early 1990s. It was shown that the inherent periodicity of auditory rhythmic patterns could entrain movement patterns in patients with movement disorders (see for a review: Thaut et al., 1999). Physiological, kinematic, and behavioral movement analysis showed very quickly that entrainment cues not only changed the timing of movement but also improved spatial and force parameters. Mathematical models have shown that anticipatory rhythmic templates as critical time constraints can result in the complete specification of the dynamics of a movement over the entire movement cycle, thereby optimizing motor planning and execution. Furthermore, temporal rhythmic entrainment has been successfully extended into applications in cognitive rehabilitation and speech and language rehabilitation, and thus become one of the major neurological mechanisms linking music and rhythm to brain rehabilitation. These findings provided a scientific basis for the development of neurologic music therapy. PMID:25774137

  12. Neurobiological Foundations of Neurologic Music Therapy: Rhythmic Entrainment and the Motor System

    Directory of Open Access Journals (Sweden)

    Michael eThaut

    2015-02-01

    Full Text Available AbstractEntrainment is defined by a temporal locking process in which one system’s motion or signal frequency entrains the frequency of another system. This process is a universal phenomenon that can be observed in physical (e.g., pendulum clocks and biological systems (e.g. fire flies. However, entrainment can also be observed between human sensory and motor systems. The function of rhythmic entrainment in rehabilitative training and learning was established for the first time by Thaut and colleagues in several research studies in the early 1990s. It was shown that the inherent periodicity of auditory rhythmic patterns could entrain movement patterns in patients with movement disorders (see for a review: Thaut et al, 1999. Physiological, kinematic and behavioral movement analysis showed very quickly that entrainment cues not only changed the timing of movement but also improved spatial and force parameters. Mathematical models have shown that anticipatory rhythmic templates as critical time constraints can result in the complete specification of the dynamics of a movement over the entire movement cycle, thereby optimizing motor planning and execution. Furthermore, temporal rhythmic entrainment has been successfully extended into applications in cognitive rehabilitation and speech and language rehabilitation, and thus become one of the major neurological mechanisms linking music and rhythm to brain rehabilitation. These findings provided a scientific basis for the development of Neurologic Music Therapy.

  13. Speech Rate Entrainment in Children and Adults With and Without Autism Spectrum Disorder.

    Science.gov (United States)

    Wynn, Camille J; Borrie, Stephanie A; Sellers, Tyra P

    2018-05-03

    Conversational entrainment, a phenomenon whereby people modify their behaviors to match their communication partner, has been evidenced as critical to successful conversation. It is plausible that deficits in entrainment contribute to the conversational breakdowns and social difficulties exhibited by people with autism spectrum disorder (ASD). This study examined speech rate entrainment in children and adult populations with and without ASD. Sixty participants including typically developing children, children with ASD, typically developed adults, and adults with ASD participated in a quasi-conversational paradigm with a pseudoconfederate. The confederate's speech rate was digitally manipulated to create slow and fast speech rate conditions. Typically developed adults entrained their speech rate in the quasi-conversational paradigm, using a faster rate during the fast speech rate conditions and a slower rate during the slow speech rate conditions. This entrainment pattern was not evident in adults with ASD or in children populations. Findings suggest that speech rate entrainment is a developmentally acquired skill and offers preliminary evidence of speech rate entrainment deficits in adults with ASD. Impairments in this area may contribute to the conversational breakdowns and social difficulties experienced by this population. Future work is needed to advance this area of inquiry.

  14. Estimation of convective entrainment properties from a cloud-resolving model simulation during TWP-ICE

    Science.gov (United States)

    Zhang, Guang J.; Wu, Xiaoqing; Zeng, Xiping; Mitovski, Toni

    2016-10-01

    The fractional entrainment rate in convective clouds is an important parameter in current convective parameterization schemes of climate models. In this paper, it is estimated using a 1-km-resolution cloud-resolving model (CRM) simulation of convective clouds from TWP-ICE (the Tropical Warm Pool-International Cloud Experiment). The clouds are divided into different types, characterized by cloud-top heights. The entrainment rates and moist static energy that is entrained or detrained are determined by analyzing the budget of moist static energy for each cloud type. Results show that the entrained air is a mixture of approximately equal amount of cloud air and environmental air, and the detrained air is a mixture of ~80 % of cloud air and 20 % of the air with saturation moist static energy at the environmental temperature. After taking into account the difference in moist static energy between the entrained air and the mean environment, the estimated fractional entrainment rate is much larger than those used in current convective parameterization schemes. High-resolution (100 m) large-eddy simulation of TWP-ICE convection was also analyzed to support the CRM results. It is shown that the characteristics of entrainment rates estimated using both the high-resolution data and CRM-resolution coarse-grained data are similar. For each cloud category, the entrainment rate is high near cloud base and top, but low in the middle of clouds. The entrainment rates are best fitted to the inverse of in-cloud vertical velocity by a second order polynomial.

  15. Impact of Air Entraining Method on the Resistance of Concrete to Internal Cracking

    Science.gov (United States)

    Wawrzeńczyk, Jerzy; Molendowska, Agnieszka

    2017-10-01

    This paper presents the test results of air entrained concrete mixtures made at a constant W/C ratio of 0.44. Three different air entraining agents were used: polymer microspheres, glass microspheres and a conventional air entraining admixture. The aim of this study was to compare the effectiveness of the air entraining methods. Concrete mixture tests were performed for consistency (slump test), density and, in the case of AEA series, air content by pressure method. Hardened concrete tests were performed for compressive strength, water absorption, resistance to chloride ingress, and freeze-thaw durability - resistance to internal cracking tests were conducted in accordance with PN-88/B-06250 on cube specimens and with the modified ASTM C666 A test method on beam specimens; porosity characteristics (A, A300, \\bar L) were determined to PN-EN 480-11:1998. No significant mass and length changes were recorded for the concrete air entrained with the conventional methods or with polymer microspheres. The results indicate that polymer microspheres are a very good alternative to traditional air entraining methods for concrete, providing effective air entrainment and protection from freezing and thawing. The glass microsphere-based concretes showed insufficient freeze-thaw resistance. The test results indicate that both the conventional methods (AEA) and the air entrainment by polymer microspheres are effective air entraining methods. It has to be noted that in the case of the use of polymer microspheres, a comparable value of \\bar L and a very good freeze-thaw resistance can be achieved at a noticeably lower air and micropore contents and at lower strength loss.

  16. Reflooding phase of the LOCA - state of the art II. Rewetting and liquid entrainment

    International Nuclear Information System (INIS)

    Elias, E.; Yadigaroglu, G.

    1977-01-01

    Understanding the mechanisms by which hot fuel rods quench and the physics of liquid droplet entrainment is important for the analysis of the reflooding phase of the LOCA. Published models of the rewetting process include simple one-dimensional solutions. The basic physical assumptions of these models and the numerical values assigned to the various parameters, as well as empirical rewetting correlations are discussed. The various mechanisms for liquid droplet entrainment and analytical formulations of the critical gas velocity and of the droplet diameter at the onset of entrainment are reviewed

  17. Effects of entrainment through Oconee Nuclear Station on carbon-14 assimilation rates of phytoplankton

    International Nuclear Information System (INIS)

    Kreh, T.V.; Derwort, J.E.

    1976-01-01

    Carbon assimilation rates of phytoplankton communities entrained through Oconee Nuclear Station were measured on six dates during 1974. Thermal, mechanical, condenser, and multiple entrainment effects on uptake rates were compared by incubating samples in vitro in controlled-temperature water baths. Duplicate light and dark bottles containing water from four cooling-system locations were exposed to temperatures approximating intake and discharge temperatures. The relationships were variable, but exposure of the hypolimnetic intake water at near-discharge temperatures (thermal effect) stimulated primary productivity in four of six experiments. Multiple entrainment and mechanical effects caused no consistent change in assimilation rates

  18. A model study of mixing and entrainment in the horizontally evolving atmospheric convective boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Fedorovich, E.; Kaiser, R. [Univ. Karlsruhe, Inst. fuer Hydrologie und Wasserwirtschaft (Germany)

    1997-10-01

    We present results from a parallel wind-tunnel/large-eddy simulation (LES) model study of mixing and entrainment in the atmospheric convective boundary layer (CBL) longitudinally developing over a heated surface. The advection-type entrainment of warmer air from upper turbulence-free layers into the growing CBL has been investigated. Most of numerical and laboratory model studies of the CBL carried out so far dealt with another type of entrainment, namely the non-steady one, regarding the CBL growth as a non-stationary process. In the atmosphere, both types of the CBL development can take place, often being superimposed. (au)

  19. A hybrid model to predict the entrainment and subsurface transport of oil

    International Nuclear Information System (INIS)

    Spaulding, M.L.; Odulo, A.; Kolluru, V.S.

    1992-01-01

    The entrainment of surface oil into the water column and its subsequent subsurface transport and dispersion are predicted by a hybrid analytic-numerical solution to the advective diffusion equation. Total oil or selected hydrocarbon component concentrations in the water column are predicted. Assuming that the principal mechanism for entrainment is due to breaking waves, the oil entrainment rate is specified using the empirically based algorithm of Delvigne and Sweeney (1988). The subsurface transport model explicitly accounts for buoyant forces on dispersed oil by droplet size. Application of the model to an analytic test case and several hypothetical scenarios illustrates the model's utility. 35 refs., 8 figs., 2 tabs

  20. Study on applicability of numerical simulation to evaluation of gas entrainment due to free surface vortex

    International Nuclear Information System (INIS)

    Ito, Kei; Kunugi, Tomoaki; Ohshima, Hiroyuki

    2008-01-01

    An onset condition of gas entrainment (GE) due to free surface vortex has been studied to establish a design of sodium-cooled fast reactor with a higher coolant velocity than conventional designs. Numerous investigations have been conducted experimentally and theoretically; however, the universal onset condition of the GE has not been determined yet due to the nonlinear characteristics of the GE. Recently, we have been studying numerical simulation methods as a promising method to evaluate GE, instead of the reliable but costly real-scale tests. In this paper, the applicability of the numerical simulation methods to the evaluation of the GE is discussed. For the purpose, a quasi-steady vortex in a cylindrical tank and a wake vortex (unsteady vortex) in a rectangular channel were numerically simulated using the volume-of-fluid type two-phase flow calculation method. The simulated velocity distributions and free surface shapes of the quasi-steady vortex showed good (not perfect, however) agreements with experimental results when a fine mesh subdivision and a high-order discretization scheme were employed. The unsteady behavior of the wake vortex was also simulated with high accuracy. Although the onset condition of the GE was slightly underestimated in the simulation results, the applicability of the numerical simulation methods to the GE evaluation was confirmed. (author)

  1. Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

    Science.gov (United States)

    Dalla Barba, Federico; Picano, Francesco

    2018-03-01

    The evaporation of droplets within turbulent sprays involves unsteady, multiscale, and multiphase processes which make its comprehension and modeling capabilities still limited. The present work aims to investigate the dynamics of droplet vaporization within a turbulent spatial developing jet in dilute, nonreacting conditions. We address the problem considering a turbulent jet laden with acetone droplets and using the direct numerical simulation framework based on a hybrid Eulerian-Lagrangian approach and the point droplet approximation. A detailed statistical analysis of both phases is presented. In particular, we show how crucial is the preferential sampling of the vapor phase induced by the inhomogeneous localization of the droplets through the flow. Strong droplet preferential segregation develops suddenly downstream from the inflow section both within the turbulent core and the jet mixing layer. Two distinct mechanisms have been found to drive this phenomenon: the inertial small-scale clustering in the jet core and the intermittent dynamics of droplets across the turbulent-nonturbulent interface in the mixing layer, where dry air entrainment occurs. These phenomenologies strongly affect the overall vaporization process and lead to an impressive widening of the droplet size and vaporization rate distributions in the downstream evolution of the turbulent spray.

  2. Study of droplet entrainment from bubbling surface in a bubble column

    International Nuclear Information System (INIS)

    Ramirez de Santiago, M.

    1991-05-01

    In a bubble column droplets are ejected from the free surface by bubble bursting or splashing. Depending on their size, the droplets are partly carried away by the streaming gas or fall back to the bubbling surface by gravity force. Experiments have been carried out to determine the void fraction in the column by means of an optical probe. In the interfacial zone the bubble bursting process was captured with a high-speed video camera. Simultaneous measurements were made of size and velocity of droplets at several distances from the bubbling surface with a Phase-Doppler Anemometry. The bubble column can be divided into three regions: A lower zone with a flat profile of the local void fraction, a central zone where the flow regime is steady and an upper zone where the local void fraction grows rapidly. A two-parameter log-normal distribution function was proposed in order to describe the polydisperse distribution of droplet-size. Results were obtained concerning the entrainment, concentration, volume fraction and interfacial area of droplets. Finally, it was found that the turbulence intensity affects the droplet terminal velocity for droplets smaller than the Kolmogorov microscale [fr

  3. Engine jet entrainment in the near field of an aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, F.; Jacquin, L.; Laverdant, A. [Office National d`Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)

    1997-12-31

    A simplified approach has been applied to analyse the mixing and entrainment processes of the engine exhaust through their interaction with the vortex wake of an aircraft. These investigations are focused on the near filed, extending from exit nozzle to the beginning of the vortex phase (i.e. to about twenty seconds after the wake is generated). This study is performed using an integral model and a numerical simulation for a two-engine large civil aircraft. The properties of the wing-tip vortices on the calculation of the dilution ratio (defined as a tracer concentration) have been shown. The mixing process is also affected by the buoyancy effect, but only after the jet regime, when the trapping in the vortex core has occurred. Qualitative comparison with contrail photography shows similar features. Finally the distortion and stretching of the plume streamlines inside the vortices can be observed, and the role of the descent of the vortices on the maximum tracer concentration has been discussed. (author) 19 refs.

  4. Spontaneous eye blinks are entrained by finger tapping.

    Science.gov (United States)

    Cong, D-K; Sharikadze, M; Staude, G; Deubel, H; Wolf, W

    2010-02-01

    We studied the mutual cross-talk between spontaneous eye blinks and continuous, self-paced unimanual and bimanual tapping. Both types of motor activities were analyzed with regard to their time-structure in synchronization-continuation tapping tasks which involved different task instructions, namely "standard" finger tapping (Experiment 1), "strong" tapping (Experiment 2) requiring more forceful finger movements, and "impulse-like" tapping (Experiment 3) where upward-downward finger movements had to be very fast. In a further control condition (Experiment 4), tapping was omitted altogether. The results revealed a prominent entrainment of spontaneous blink behavior by the manual tapping, with bimanual tapping being more effective than unimanual tapping, and with the "strong" and "impulse-like" tapping showing the largest effects on blink timing. Conversely, we found no significant effects of the tapping on the timing of the eye blinks across all experiments. The findings suggest a functional overlap of the motor control structures responsible for voluntary, rhythmic finger movements and eye blinking behavior.

  5. Engine jet entrainment in the near field of an aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, F; Jacquin, L; Laverdant, A [Office National d` Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)

    1998-12-31

    A simplified approach has been applied to analyse the mixing and entrainment processes of the engine exhaust through their interaction with the vortex wake of an aircraft. These investigations are focused on the near filed, extending from exit nozzle to the beginning of the vortex phase (i.e. to about twenty seconds after the wake is generated). This study is performed using an integral model and a numerical simulation for a two-engine large civil aircraft. The properties of the wing-tip vortices on the calculation of the dilution ratio (defined as a tracer concentration) have been shown. The mixing process is also affected by the buoyancy effect, but only after the jet regime, when the trapping in the vortex core has occurred. Qualitative comparison with contrail photography shows similar features. Finally the distortion and stretching of the plume streamlines inside the vortices can be observed, and the role of the descent of the vortices on the maximum tracer concentration has been discussed. (author) 19 refs.

  6. Colour As a Signal for Entraining the Mammalian Circadian Clock

    Science.gov (United States)

    Walmsley, Lauren; Hanna, Lydia; Mouland, Josh; Martial, Franck; West, Alexander; Smedley, Andrew R.; Bechtold, David A.; Webb, Ann R.; Lucas, Robert J.; Brown, Timothy M.

    2015-01-01

    Twilight is characterised by changes in both quantity (“irradiance”) and quality (“colour”) of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue–yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision. PMID:25884537

  7. Colour as a signal for entraining the mammalian circadian clock.

    Directory of Open Access Journals (Sweden)

    Lauren Walmsley

    2015-04-01

    Full Text Available Twilight is characterised by changes in both quantity ("irradiance" and quality ("colour" of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue-yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

  8. Familiarity Affects Entrainment of EEG in Music Listening

    Directory of Open Access Journals (Sweden)

    Yuiko Kumagai

    2017-07-01

    Full Text Available Music perception involves complex brain functions. The relationship between music and brain such as cortical entrainment to periodic tune, periodic beat, and music have been well investigated. It has also been reported that the cerebral cortex responded more strongly to the periodic rhythm of unfamiliar music than to that of familiar music. However, previous works mainly used simple and artificial auditory stimuli like pure tone or beep. It is still unclear how the brain response is influenced by the familiarity of music. To address this issue, we analyzed electroencelphalogram (EEG to investigate the relationship between cortical response and familiarity of music using melodies produced by piano sounds as simple natural stimuli. The cross-correlation function averaged across trials, channels, and participants showed two pronounced peaks at time lags around 70 and 140 ms. At the two peaks the magnitude of the cross-correlation values were significantly larger when listening to unfamiliar and scrambled music compared to those when listening to familiar music. Our findings suggest that the response to unfamiliar music is stronger than that to familiar music. One potential application of our findings would be the discrimination of listeners' familiarity with music, which provides an important tool for assessment of brain activity.

  9. Flooding and flow reversal of two-phase annular flow

    International Nuclear Information System (INIS)

    Asahi, Y.

    1978-01-01

    The flooding and flow reversal conditions of two-phase annular flow are mathematically defined in terms of a characteristic function representing a force balance. Sufficiently below the flooding point in counter-current flow, the interface is smooth and the characteristic equation reduces to the Nusselt relationship. Just below flooding point and above the flow reversal point in cocurrent flow, the interface is 'wavy', so that the interfacial shear effect plays an important role. The theoretical analysis is compared with experimental results by others. It is suggested that the various length effects which have been experimentally observed may be accounted for by the spatial variation of the droplet entrainment. (Auth.)

  10. Annular dispersed flow analysis model by Lagrangian method and liquid film cell method

    International Nuclear Information System (INIS)

    Matsuura, K.; Kuchinishi, M.; Kataoka, I.; Serizawa, A.

    2003-01-01

    A new annular dispersed flow analysis model was developed. In this model, both droplet behavior and liquid film behavior were simultaneously analyzed. Droplet behavior in turbulent flow was analyzed by the Lagrangian method with refined stochastic model. On the other hand, liquid film behavior was simulated by the boundary condition of moving rough wall and liquid film cell model, which was used to estimate liquid film flow rate. The height of moving rough wall was estimated by disturbance wave height correlation. In each liquid film cell, liquid film flow rate was calculated by considering droplet deposition and entrainment flow rate. Droplet deposition flow rate was calculated by Lagrangian method and entrainment flow rate was calculated by entrainment correlation. For the verification of moving rough wall model, turbulent flow analysis results under the annular flow condition were compared with the experimental data. Agreement between analysis results and experimental results were fairly good. Furthermore annular dispersed flow experiments were analyzed, in order to verify droplet behavior model and the liquid film cell model. The experimental results of radial distribution of droplet mass flux were compared with analysis results. The agreement was good under low liquid flow rate condition and poor under high liquid flow rate condition. But by modifying entrainment rate correlation, the agreement become good even under high liquid flow rate. This means that basic analysis method of droplet and liquid film behavior was right. In future work, verification calculation should be carried out under different experimental condition and entrainment ratio correlation also should be corrected

  11. REGSOLexpert: Entrainer Selection Tool for waste solvent recovery by batch distillation processes

    OpenAIRE

    Rodriguez-Donis, Ivonne; Gerbaud, Vincent; Baudouin, Olivier; Joulia, Xavier

    2009-01-01

    A general procedure to systematize the search of several alternatives enabling the separation of non-ideal binary mixtures such as pressure-swing distillation, azeotropic and extractive distillation is presented. The use of heterogeneous entrainers is specially highlighted.

  12. What is the functional relevance of prefrontal cortex entrainment to hippocampal theta rhythms?

    Directory of Open Access Journals (Sweden)

    James Michael Hyman

    2011-03-01

    Full Text Available There has been considerable interest in the importance of oscillations in the brain and in how these oscillations relate to the firing of single neurons. Recently a number of studies have shown that the spiking of individual neurons in the medial prefrontal cortex (mPFC become entrained to the hippocampal (HPC theta rhythm. We recently showed that theta-entrained mPFC cells lost theta-entrainment specifically on error trials even though the firing rates of these cells did not change (Hyman et al., 2010. This implied that the level of HPC theta-entrainment of mPFC units was more predictive of trial outcome than differences in firing rates and that there is more information encoded by the mPFC on working memory tasks than can be accounted for by a simple rate code. Nevertheless, the functional meaning of mPFC entrainment to HPC theta remains a mystery. It is also unclear as to whether there are any differences in the nature of the information encoded by theta-entrained and non-entrained mPFC cells. In this review we discuss mPFC entrainment to HPC theta within the context of previous results as well as provide a more detailed analysis of the Hyman et al. (2010 data set. This re-analysis revealed that theta-entrained mPFC cells selectively encoded a variety of task relevant behaviors and stimuli while never theta-entrained mPFC cells were most strongly attuned to errors or the lack of expected rewards. In fact, these error responsive neurons were responsible for the error representations exhibited by the entire ensemble of mPFC neurons. A theta reset was also detected in the post-error period. While it is becoming increasingly evident that mPFC neurons exhibit correlates to virtually all cues and behaviors, perhaps phase-locking directs attention to the task-relevant representations required to solve a spatially based working memory task while the loss of theta-entrainment at the start of error trials may represent a shift of attention away from

  13. Conceptual design of heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer

    OpenAIRE

    Paritta Prayoonyong

    2014-01-01

    The synthesis of a heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer is presented. The residue curve map of the ethanol/water/1-butanol mixture is computationally generated using non-random twoliquid thermodynamic model. It is found that 1-butanol leads to a residue curve map topological structure different from that generated by typical entrainers used in ethanol dehydration. Synthesis...

  14. Neural entrainment to rhythmically-presented auditory, visual and audio-visual speech in children

    Directory of Open Access Journals (Sweden)

    Alan James Power

    2012-07-01

    Full Text Available Auditory cortical oscillations have been proposed to play an important role in speech perception. It is suggested that the brain may take temporal ‘samples’ of information from the speech stream at different rates, phase-resetting ongoing oscillations so that they are aligned with similar frequency bands in the input (‘phase locking’. Information from these frequency bands is then bound together for speech perception. To date, there are no explorations of neural phase-locking and entrainment to speech input in children. However, it is clear from studies of language acquisition that infants use both visual speech information and auditory speech information in learning. In order to study neural entrainment to speech in typically-developing children, we use a rhythmic entrainment paradigm (underlying 2 Hz or delta rate based on repetition of the syllable ba, presented in either the auditory modality alone, the visual modality alone, or as auditory-visual speech (via a talking head. To ensure attention to the task, children aged 13 years were asked to press a button as fast as possible when the ba stimulus violated the rhythm for each stream type. Rhythmic violation depended on delaying the occurrence of a ba in the isochronous stream. Neural entrainment was demonstrated for all stream types, and individual differences in standardized measures of language processing were related to auditory entrainment at the theta rate. Further, there was significant modulation of the preferred phase of auditory entrainment in the theta band when visual speech cues were present, indicating cross-modal phase resetting. The rhythmic entrainment paradigm developed here offers a method for exploring individual differences in oscillatory phase locking during development. In particular, a method for assessing neural entrainment and cross-modal phase resetting would be useful for exploring developmental learning difficulties thought to involve temporal sampling

  15. Study on cocurrent downtake gas-liquid flow in a vertical channel

    International Nuclear Information System (INIS)

    Lozovetskij, V.V.

    1978-01-01

    Hydraulic resistance and liquid stall from the film surface at cocurrent film and gas downflow in vertical channel in measurement range of reynolds number from 100 to 1260 for the film and from 1.2x10 4 to 10 5 for gas are studied. For downflow two regimes are characteristic: purely annular, that is separate phase flow regime, and the regime of stall and carrying liquid droplets from the film surface, that is annular dispersed flow regime. The existence boundaries of both regimes are determined and criterial equations for pressure drop calculation are obtained. It is established experimentally that at sufficient range from the liquid input place on the working zone the established two-phase flow takes place. In their nucleus two areas can be singled out, which differ by the flow density values of stalled liquid: central, having the permanent flow density value and area adjacent to the film surface, the liquid in the combs of waves making a significant contribution to the flow density value. At equal flooding density with the relative gas speed increase, the flow density value of stalled liquid in the channel central part increase. A similar result also takes place at flooding density increase at permanent relative speed. Flooding density and relative speed increase leads to levelling stalled liquid distribution about the channel cross section

  16. The role of the endocrine system in feeding-induced tissue-specific circadian entrainment.

    Science.gov (United States)

    Sato, Miho; Murakami, Mariko; Node, Koichi; Matsumura, Ritsuko; Akashi, Makoto

    2014-07-24

    The circadian clock is entrained to environmental cycles by external cue-mediated phase adjustment. Although the light input pathway has been well defined, the mechanism of feeding-induced phase resetting remains unclear. The tissue-specific sensitivity of peripheral entrainment to feeding suggests the involvement of multiple pathways, including humoral and neuronal signals. Previous in vitro studies with cultured cells indicate that endocrine factors may function as entrainment cues for peripheral clocks. However, blood-borne factors that are well characterized in actual feeding-induced resetting have yet to be identified. Here, we report that insulin may be involved in feeding-induced tissue-type-dependent entrainment in vivo. In ex vivo culture experiments, insulin-induced phase shift in peripheral clocks was dependent on tissue type, which was consistent with tissue-specific insulin sensitivity, and peripheral entrainment in insulin-sensitive tissues involved PI3K- and MAPK-mediated signaling pathways. These results suggest that insulin may be an immediate early factor in feeding-mediated tissue-specific entrainment. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Secondary Rayleigh-Taylor Instabilities in the Reconnection Exhaust Jet: A Mechanism for Supra-Arcade Downflows in the Solar Corona

    Science.gov (United States)

    Guo, L.; Bhattacharjee, A.; Huang, Y. M.; Innes, D.

    2014-12-01

    Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features usually observed in active-region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright, upward moving spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for decades, the mechanism for formation of SADs remains an open issue. Using high-Lundquist-number three-dimensional resistive MHD simulations, we demonstrate that secondary Rayleigh-Taylor type instabilities develop in the downstream region of a reconnecting current sheet. The instability results in the formation of low-density coherent structures that resemble SADs, intertwined with high-density structures that appear to be spike-like. Using SDO/AIA images, we highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with siumlations suggest that secondary Rayleigh-Taylor type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs and spikes. Although the plasma conditions are vastly different, analogous phenomena also occur in the Earth's magnetotail during reconnection.

  18. Recovery and biological oxidation of dissolved methane in effluent from UASB treatment of municipal sewage using a two-stage closed downflow hanging sponge system.

    Science.gov (United States)

    Matsuura, Norihisa; Hatamoto, Masashi; Sumino, Haruhiko; Syutsubo, Kazuaki; Yamaguchi, Takashi; Ohashi, Akiyoshi

    2015-03-15

    A two-stage closed downflow hanging sponge (DHS) reactor was used as a post-treatment to prevent methane being emitted from upflow anaerobic sludge blanket (UASB) effluents containing unrecovered dissolved methane. The performance of the closed DHS reactor was evaluated using real municipal sewage at ambient temperatures (10-28 °C) for one year. The first stage of the closed DHS reactor was intended to recover dissolved methane from the UASB effluent and produce a burnable gas with a methane concentration greater than 30%, and its recovery efficiency was 57-88%, although the amount of dissolved methane in the UASB effluent fluctuated in the range of 46-68 % of methane production greatly depending on the temperature. The residual methane was oxidized and the remaining organic carbon was removed in the second closed DHS reactor, and this reactor performed very well, removing more than 99% of the dissolved methane during the experimental period. The rate at which air was supplied to the DHS reactor was found to be one of the most important operating parameters. Microbial community analysis revealed that seasonal changes in the methane-oxidizing bacteria were key to preventing methane emissions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Analysis of clad motion observed in loss of flow accident simulation experiments

    International Nuclear Information System (INIS)

    Henkel, P.R.

    1987-01-01

    The clad motion observed in the first two STAR experiments is analysed. The movies reveal that at moderate temperatures molten cladding does not wet fresh fuel (within an argon gas atmosphere). The prevailing flow regime consists of single waves contacting the fuel pins and entrained drops. Entrainment is possible already at gas velocities of order 40-50 m/s. A multichannel clad motion model is presented that accounts for both flow modes. (author)

  20. Influence of entrainment and countergradient on the ABL diurnal development

    Science.gov (United States)

    Hernández-Ceballos, M. A.

    2009-09-01

    The representation of the diurnal evolution of the boundary layer (ABL) by NCAR-Penn State Mesoscale Model (MM5) and by the mesoscale model Weather Research Forecast (WRF) is compared. Special attention is paid to determine the role of processes that occur near and below the inversion zone: the positive correlation between the heat flux and the gradient (countergradient) and the role of entrainment of heat originating from the free troposphere. Both processes play a key role in the modelling of the diurnal variability of temperature, moisture and atmospheric compounds. A number of 13 simulations are carried out to determine the sensitivity of the model results to the formulation of the ABL height and countergradient heat flux in the Medium Range Forecast (MRF) ABL scheme. Model results are compared with experimental data obtained from the DOMINO (Diel Oxidant Mechanisms in relation to Nitrogen oxides) campaign. It was organized by Max Planck Institute for Atmospheric Chemistry (Germany) in collaboration with the National Institute for Aerospace Technology (Spain). The DOMINO campaign took place at the "Atmospheric Sounding Station - El Arenosillo", a platform dedicated to atmospheric measurements in the Southwest of Spain. All numerical experiments are grouped in four clusters, each focussing on the sensitivity of different relevant aspects. The following aspects of the formulation are analyzed: surface moisture availability (M), the countergradient term (γc) and the ABL height (h). This is done by modifying both the bulk critical Richardson number (Ric) at the inversion zone, and a coefficient of proportionality (b) that determines the excess temperature and countergradient. The importance of b is due to its direct relation in the definition of both, γc and h. The results got with MM5 model show that temperature and specific moisture temporal evolution is not very sensitive to changes in the soil moisture availability (M value from 0.6 to 0.1). Using the MRF

  1. Liquid entrainment and off-take through the break at the top of a vessel

    International Nuclear Information System (INIS)

    Kim, Chang Hyun; No, Hee Cheon

    2005-01-01

    In order to determine the bleed capacity of the safety depressurization system (SDS) of Advanced Power Reactor 1400 (APR1400) in the case of total loss of feed water (TLOFW), we performed an experimental study of liquid entrainment and liquid off-take from the swelled two-phase mixture surface in a vessel. A total of 220 experimental data on the entrainment and off-take are obtained using a test vessel with a height of 2.0m and an inner diameter of 0.3m and a top break with a diameter of 0.05m. Two-phase mixture levels are measured by an ultrasonic sensor within +/-1.77% with respect to the visual level data. Droplet entrainment data are obtained with and without the top break and are compared with the existing pool entrainment data. The present droplet entrainment data have higher values than the existing pool entrainment data due to (a) the pulling toward the break of the liquid deentrained on the top wall of the vessel and (b) gas acceleration in the vicinity of the break. In the present experiment, droplet entrainment, E fg , strongly depends upon j g * /h * and is proportional to the seventh power of j g * /h * in the same way as the off-take data. The empirical correlation for the onset of off-take is developed in terms of the Froude number (Fr g ) at the break and the non-dimensional inception height (h b /d). This correlation shows agreement with the present experimental data within +/-15%. The present off-take quality data show agreement with Schrock's off-take quality correlation with the rms error of 15.8%

  2. Liquid entrainment and off-take from the two-phase mixture surface in a vessel

    International Nuclear Information System (INIS)

    Kim, Chang Hyun; No, Hee Cheon

    2003-01-01

    In order to determine the bleed capacity of the Safety Depressurization System (SDS) of Advanced Power Reactor 1400 (APR1400) in the case of Total Loss of Feed Water (TLOFW), we performed an experimental study of liquid entrainment and liquid off-take from the swelled two-phase mixture surface in a vessel. A total of 220 experimental data on the entrainment and off-take are obtained using a test vessel with a height of 2.0m and an inner diameter of 0.3m, and a top break with a diameter of 0.05m. Two-phase mixture levels are measured by an ultrasonic sensor within ±1.77% with respect to the visual level data. Droplet entrainment data are obtained with and without the top break and are compared with the existing pool entrainment data. The present droplet entrainment data have higher values than those of the existing pool entrainment due to (a) the pulling toward the break of the liquid deentrained on the top wall of the vessel and (b) gas acceleration in the vicinity of the break. In the present experiment, droplet entrainment, Efg, strongly depends upon jg/h and is proportional to the 7th power of jg/h in the same way as the off-take data. The empirical correlation for the onset of off-take is developed in terms of the Froude number (Frg) at the break and the non-dimensional inception height (hb/d). This correlation shows agreement with the present experimental data within ±15%. The present off-take quality data show agreement with Schrock's off-take quality correlation with the r.m.s. error of 15.8%

  3. Fish-protection devices at unscreened water diversions can reduce entrainment: evidence from behavioural laboratory investigations

    Science.gov (United States)

    Poletto, Jamilynn B.; Cocherell, Dennis E.; Mussen, Timothy D.; Ercan, Ali; Bandeh, Hossein; Kavvas, M. Levent; Cech, Joseph J.; Fangue, Nann A.

    2015-01-01

    Diversion (i.e. extraction) of water from rivers and estuaries can potentially affect native wildlife populations if operation is not carefully managed. For example, open, unmodified water diversions can act as a source of injury or mortality to resident or migratory fishes from entrainment and impingement, and can cause habitat degradation and fragmentation. Fish-protection devices, such as exclusion screens, louvres or sensory deterrents, can physically or behaviourally deter fish from approaching or being entrained into water diversions. However, empirical assessment of their efficacy is often lacking or is investigated only for particular economically or culturally important fishes, such as salmonids. The Southern population of anadromous green sturgeon (Acipenser medirostris) is listed as threatened in California, and there is a high density of water diversions located within their native range (the Sacramento–San Joaquin watershed). Coupled with their unique physiology and behaviour compared with many other fishes native to California, the green sturgeon is susceptible to entrainment into diversions and is an ideal species with which to study the efficacy of mitigation techniques. Therefore, we investigated juvenile green sturgeon (188–202 days post-hatch) in the presence of several fish-protection devices to assess behaviour and entrainment risk. Using a large experimental flume (∼500 kl), we found that compared with an open diversion pipe (control), the addition of a trash-rack box, louvre box, or perforated cylinder on the pipe inlet all significantly reduced the proportion of fish that were entrained through the pipe (P = 0.03, P = 0.028, and P = 0.028, respectively). Likewise, these devices decreased entrainment risk during a single movement past the pipe by between 60 and 96%. These fish-protection devices should decrease the risk of fish entrainment during water-diversion activities. PMID:27293725

  4. Entrainment and mixing in a laboratory model of oceanic overflow

    OpenAIRE

    Odier , Philippe; Chen , Jun; Ecke , Robert

    2014-01-01

    International audience; We present experimental measurements of a wall-bounded gravity current, motivated by characterizing natural gravity currents such as oceanic overflows. We use particle image velocimetry and planar laser-induced fluorescence to simultaneously measure the velocity and density fields as they evolve downstream of the initial injection from a turbulent channel flow onto a plane inclined at 10 degrees with respect to horizontal. The turbulence level of the input flow is cont...

  5. Measurements on Buoyant Jet Flows from a Ceiling-Mounted Slot Diffuser

    DEFF Research Database (Denmark)

    Nielsen, Peter V.; Möller, Åke T. A.

    Ceiling-mounted slot diffusers in ventilated rooms will often generate a flow of the wall jet type. The jet follows the ceiling, entrains air from the occupied zone and generates a recirculating flow in the whole room. This paper will deal with the flow in the ceiling region. The wall jet flow...

  6. Uncertainty associated with convective wet removal of entrained aerosols in a global climate model

    Directory of Open Access Journals (Sweden)

    B. Croft

    2012-11-01

    Full Text Available The uncertainties associated with the wet removal of aerosols entrained above convective cloud bases are investigated in a global aerosol-climate model (ECHAM5-HAM under a set of limiting assumptions for the wet removal of the entrained aerosols. The limiting assumptions for the wet removal of entrained aerosols are negligible scavenging and vigorous scavenging (either through activation, with size-dependent impaction scavenging, or with the prescribed fractions of the standard model. To facilitate this process-based study, an explicit representation of cloud-droplet-borne and ice-crystal-borne aerosol mass and number, for the purpose of wet removal, is introduced into the ECHAM5-HAM model. This replaces and is compared with the prescribed cloud-droplet-borne and ice-crystal-borne aerosol fraction scavenging scheme of the standard model.

    A 20% to 35% uncertainty in simulated global, annual mean aerosol mass burdens and optical depth (AOD is attributed to different assumptions for the wet removal of aerosols entrained above convective cloud bases. Assumptions about the removal of aerosols entrained above convective cloud bases control modeled upper tropospheric aerosol concentrations by as much as one order of magnitude.

    Simulated aerosols entrained above convective cloud bases contribute 20% to 50% of modeled global, annual mean aerosol mass convective wet deposition (about 5% to 10% of the total dry and wet deposition, depending on the aerosol species, when including wet scavenging of those entrained aerosols (either by activation, size-dependent impaction, or with the prescribed fraction scheme. Among the simulations, the prescribed fraction and size-dependent impaction schemes yield the largest global, annual mean aerosol mass convective wet deposition (by about two-fold. However, the prescribed fraction scheme has more vigorous convective mixed-phase wet removal (by two to five-fold relative to the size-dependent impaction

  7. Uncertainty associated with convective wet removal of entrained aerosols in a global climate model

    Science.gov (United States)

    Croft, B.; Pierce, J. R.; Martin, R. V.; Hoose, C.; Lohmann, U.

    2012-11-01

    The uncertainties associated with the wet removal of aerosols entrained above convective cloud bases are investigated in a global aerosol-climate model (ECHAM5-HAM) under a set of limiting assumptions for the wet removal of the entrained aerosols. The limiting assumptions for the wet removal of entrained aerosols are negligible scavenging and vigorous scavenging (either through activation, with size-dependent impaction scavenging, or with the prescribed fractions of the standard model). To facilitate this process-based study, an explicit representation of cloud-droplet-borne and ice-crystal-borne aerosol mass and number, for the purpose of wet removal, is introduced into the ECHAM5-HAM model. This replaces and is compared with the prescribed cloud-droplet-borne and ice-crystal-borne aerosol fraction scavenging scheme of the standard model. A 20% to 35% uncertainty in simulated global, annual mean aerosol mass burdens and optical depth (AOD) is attributed to different assumptions for the wet removal of aerosols entrained above convective cloud bases. Assumptions about the removal of aerosols entrained above convective cloud bases control modeled upper tropospheric aerosol concentrations by as much as one order of magnitude. Simulated aerosols entrained above convective cloud bases contribute 20% to 50% of modeled global, annual mean aerosol mass convective wet deposition (about 5% to 10% of the total dry and wet deposition), depending on the aerosol species, when including wet scavenging of those entrained aerosols (either by activation, size-dependent impaction, or with the prescribed fraction scheme). Among the simulations, the prescribed fraction and size-dependent impaction schemes yield the largest global, annual mean aerosol mass convective wet deposition (by about two-fold). However, the prescribed fraction scheme has more vigorous convective mixed-phase wet removal (by two to five-fold relative to the size-dependent impaction scheme) since nearly all

  8. Advances in field and analytical methods for estimating entrainment mortality factors

    International Nuclear Information System (INIS)

    Muessig, P.H.; Young, J.R.; Vaughan, D.S.; Smith, B.A.

    1988-01-01

    The hearings and settlement negotiations in the Hudson River case focused on various modeling input factors for calculating reduction in year-class strength of important fish species in the Hudson River due to power plant operations. One of the inputs that received considerable attention, and about which the various parties to the case came to general agreement, was the entrainment mortality factor, or f-factor, the probability that an entrained live organism will be killed as a result of its passage through a power plant in the condenser cooling water. Entrainment mortality includes death due to temperature increases and death due to mechanical processes. The convergence of views about the f-factor arose from increased understanding of the sources of estimation error, improvements in gear for collection of fish larvae, and development of a model for the thermal component of entrainment mortality. Improvements in sampling-gear design reduced potential biases in mortality estimates, reduced estimates of mechanical mortality from 0.923 to 0.412, and improved the statistical power to detect entrainment mortality and the precision of mortality estimates. 20 refs., 7 figs., 1 tab

  9. Assessment of the Effects of Entrainment and Wind Shear on Nuclear Cloud Rise Modeling

    Science.gov (United States)

    Zalewski, Daniel; Jodoin, Vincent

    2001-04-01

    Accurate modeling of nuclear cloud rise is critical in hazard prediction following a nuclear detonation. This thesis recommends improvements to the model currently used by DOD. It considers a single-term versus a three-term entrainment equation, the value of the entrainment and eddy viscous drag parameters, as well as the effect of wind shear in the cloud rise following a nuclear detonation. It examines departures from the 1979 version of the Department of Defense Land Fallout Interpretive Code (DELFIC) with the current code used in the Hazard Prediction and Assessment Capability (HPAC) code version 3.2. The recommendation for a single-term entrainment equation, with constant value parameters, without wind shear corrections, and without cloud oscillations is based on both a statistical analysis using 67 U.S. nuclear atmospheric test shots and the physical representation of the modeling. The statistical analysis optimized the parameter values of interest for four cases: the three-term entrainment equation with wind shear and without wind shear as well as the single-term entrainment equation with and without wind shear. The thesis then examines the effect of cloud oscillations as a significant departure in the code. Modifications to user input atmospheric tables are identified as a potential problem in the calculation of stabilized cloud dimensions in HPAC.

  10. Cognitive performance as a zeitgeber: cognitive oscillators and cholinergic modulation of the SCN entrain circadian rhythms.

    Directory of Open Access Journals (Sweden)

    Howard J Gritton

    Full Text Available The suprachiasmatic nucleus (SCN is the primary circadian pacemaker in mammals that can synchronize or entrain to environmental cues. Although light exerts powerful influences on SCN output, other non-photic stimuli can modulate the SCN as well. We recently demonstrated that daily performance of a cognitive task requiring sustained periods of attentional effort that relies upon basal forebrain (BF cholinergic activity dramatically alters circadian rhythms in rats. In particular, normally nocturnal rats adopt a robust diurnal activity pattern that persists for several days in the absence of cognitive training. Although anatomical and pharmacological data from non-performing animals support a relationship between cholinergic signaling and circadian rhythms, little is known about how endogenous cholinergic signaling influences SCN function in behaving animals. Here we report that BF cholinergic projections to the SCN provide the principal signal allowing for the expression of cognitive entrainment in light-phase trained animals. We also reveal that oscillator(s outside of the SCN drive cognitive entrainment as daily timed cognitive training robustly entrains SCN-lesioned arrhythmic animals. Ablation of the SCN, however, resulted in significant impairments in task acquisition, indicating that SCN-mediated timekeeping benefits new learning and cognitive performance. Taken together, we conclude that cognition entrains non-photic oscillators, and cholinergic signaling to the SCN serves as a temporal timestamp attenuating SCN photic-driven rhythms, thereby permitting cognitive demands to modulate behavior.

  11. Getting the beat: entrainment of brain activity by musical rhythm and pleasantness.

    Science.gov (United States)

    Trost, Wiebke; Frühholz, Sascha; Schön, Daniele; Labbé, Carolina; Pichon, Swann; Grandjean, Didier; Vuilleumier, Patrik

    2014-12-01

    Rhythmic entrainment is an important component of emotion induction by music, but brain circuits recruited during spontaneous entrainment of attention by music and the influence of the subjective emotional feelings evoked by music remain still largely unresolved. In this study we used fMRI to test whether the metric structure of music entrains brain activity and how music pleasantness influences such entrainment. Participants listened to piano music while performing a speeded visuomotor detection task in which targets appeared time-locked to either strong or weak beats. Each musical piece was presented in both a consonant/pleasant and dissonant/unpleasant version. Consonant music facilitated target detection and targets presented synchronously with strong beats were detected faster. FMRI showed increased activation of bilateral caudate nucleus when responding on strong beats, whereas consonance enhanced activity in attentional networks. Meter and consonance selectively interacted in the caudate nucleus, with greater meter effects during dissonant than consonant music. These results reveal that the basal ganglia, involved both in emotion and rhythm processing, critically contribute to rhythmic entrainment of subcortical brain circuits by music. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Effect of fast freeze-thaw cycles on mechanical properties of ordinary-air-entrained concrete.

    Science.gov (United States)

    Shang, Huai-shuai; Cao, Wei-qun; Wang, Bin

    2014-01-01

    Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions.

  13. Searching for roots of entrainment and joint action in early musical interactions

    Directory of Open Access Journals (Sweden)

    Jessica ePhillips-Silver

    2012-02-01

    Full Text Available When people play music and dance together, they engage in forms of musical joint action that are often characterized by a shared sense of rhythmic timing and affective state (i.e., temporal and affective entrainment. In order to understand the origins of musical joint action, we propose a model in which entrainment is linked to dual mechanisms (motor resonance and action simulation, which in turn support musical behavior (imitation and complementary joint action. To illustrate this model, we consider two generic forms of joint musical behavior: chorusing and turn-taking. We explore how these common behaviors can be founded on entrainment capacities established early in human development, specifically during musical interactions between infants and their caregivers. If the roots of entrainment are found in early musical interactions which are practiced from childhood into adulthood, then we propose that the rehearsal of advanced musical ensemble skills can be considered to be a refined, mimetic form of temporal and affective entrainment whose evolution begins in infancy.

  14. Interpretations of Frequency Domain Analyses of Neural Entrainment: Periodicity, Fundamental Frequency, and Harmonics.

    Science.gov (United States)

    Zhou, Hong; Melloni, Lucia; Poeppel, David; Ding, Nai

    2016-01-01

    Brain activity can follow the rhythms of dynamic sensory stimuli, such as speech and music, a phenomenon called neural entrainment. It has been hypothesized that low-frequency neural entrainment in the neural delta and theta bands provides a potential mechanism to represent and integrate temporal information. Low-frequency neural entrainment is often studied using periodically changing stimuli and is analyzed in the frequency domain using the Fourier analysis. The Fourier analysis decomposes a periodic signal into harmonically related sinusoids. However, it is not intuitive how these harmonically related components are related to the response waveform. Here, we explain the interpretation of response harmonics, with a special focus on very low-frequency neural entrainment near 1 Hz. It is illustrated why neural responses repeating at f Hz do not necessarily generate any neural response at f Hz in the Fourier spectrum. A strong neural response at f Hz indicates that the time scales of the neural response waveform within each cycle match the time scales of the stimulus rhythm. Therefore, neural entrainment at very low frequency implies not only that the neural response repeats at f Hz but also that each period of the neural response is a slow wave matching the time scale of a f Hz sinusoid.

  15. Word-by-word entrainment of speech rhythm during joint story building

    Directory of Open Access Journals (Sweden)

    Tommi eHimberg

    2015-06-01

    Full Text Available Movements and behaviour synchronise during social interaction at many levels, often unintentionally. During smooth conversation, for example, participants adapt to each others' speech rates. Here we aimed to find out to which extent speakers adapt their turn-taking rhythms during a story-building game.Nine sex-matched dyads of adults (12 males, 6 females created two 5-min stories by contributing to them alternatingly one word at a time. The participants were located in different rooms, with audio connection during one story and audiovisual during the other. They were free to select the topic of the story.Although the participants received no instructions regarding the timing of the story building, their word rhythms were highly entrained (R ̅ = 0.70, p < 0.001 even though the rhythms as such were unstable (R ̅ = 0.14 for pooled data. Such high entrainment in the absence of steady word rhythm occurred in every individual story, independently of whether the subjects were connected via audio-only or audiovisual link.The observed entrainment was of similar strength as typical entrainment in finger-tapping tasks where participants are specifically instructed to synchronize their behaviour. Thus speech seems to spontaneously induce strong entrainment between the conversation partners, likely reflecting automatic alignment of their semantic and syntactic processes.

  16. Ultrafiltration and Characterization of AW-101 Supernatant and Entrained Solids

    International Nuclear Information System (INIS)

    Brooks, K.P.; Bredt, P.R.; Golcar, G.R.; Hartley, S.A.; Urie, M.W.; Tingey, J.M.; Rappe, K.G.; Jagoda, L.K.

    1999-01-01

    The River Protection Project Waste Treatment Plant (RPP-WTP) (1996) flow sheet uses cross-flow filtration as the solid/liquid separation technique. Unlike traditional dead-end filtration, which has a declining rate caused by the growth of a filter cake on the surface of the filter medium, in cross-flow filtration, the filter cake is swept away by the fluid flowing across it. This filtration method is especially beneficial when there are very fine particles and when system simplicity is required. The objective of this work was to test cross-flow filtration using actual Envelope A Hanford tank waste. Similar to the Phase 1A study, they evaluated the permeability of an Envelope A feed through a single element filter as a function of transmembrane pressure, axial velocity, solids concentration, and time. In addition, the efficiency of back pulse and chemical cleaning on the filter performance was evaluated. The chemical and radiochemical composition of the filtrate and solids was measured to determine efficiency of the filtration process. This report describes the test apparatus, the experimental approach, the results of the tests, and the chemical and radiochemical analysis for supernatants taken from Hanford Tank AW-101. This report also provides a means of transmitting to British Nuclear Fuels, Limited (BNFL) the completed test instruction and raw filtration and analytical data

  17. Effects of Debris Entrainment and Multi-Phase Flow on Plug Loading in an MX Trench.

    Science.gov (United States)

    1978-09-15

    gas stream of density (pg) and velocity (Vg) is: -., * -) - * 2~ TD FD Pg (V P V) Vp-Vg I CD( TD ) (A.1) 4 where the drag coefficient (CD) is defined by...ATTN: FCPR ATTN: Code L53 , J. Forrest Field Command Naval Facilities Engineering Command Defense Nuclear Agency ATTN: Code 09M22C Livermore Division

  18. Entrained-Flow, Fast Ablative Pyrolysis of Biomass - Annual Report, 1 December 1984 - 31 December 1985

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, J. P.; Scahill, J. W.; Evans, R. J.

    1986-07-01

    The ablative, fast pyrolysis system was relocated to SERI's new, permanent Field Test Laboratory. Pyrolysis system modifications were made to increase the energy available to the vortex reactor and to enhance the collection efficiency of primary pyrolysis vapors. Mathematical modeling of the vapor cracker has resulted in the ability to accurately predict experimental results with respect to the thermal cracking of the primary vapors, the generation of noncondensible gases, and the gas composition. The computer algorithm of this model can be readily used to perform experimental simulation and/or reactor scale-up due to its fundamental nature. Preliminary screening tests with pure ZSM-5 zeolite catalyst, supplied by Mobil Research and Development Corporation, have shown promise for the conversion of primary pyrolysis oil vapors to aromatic hydrocarbons; i.e., gasoline.

  19. Experimental investigation into fast pyrolysis of biomass using an entrained flow reactor

    Science.gov (United States)

    Bohn, M.; Benham, C.

    1981-02-01

    Pyrolysis experiments were performed with steam as a carrier gas and two different feedstocks - wheat straw and powdered material derived from municipal solid waste (ECO-II TM). Reactor wall temperature was varied from 7000 to 1400 C. Gas composition data from the ECO-II tests were comparable to previously reported data but ethylene yield appeared to vary with reactor wall temperature and residence time. The important conclusion from the wheat straw tests is that olefin yields are about one half that obtained from ECO-II. Evidence was found that high olefin yields from ECO-II are due to the presence of plastics in the feedstock.

  20. CFD simulation of coal gasification in an entrained-flow gasifier

    DEFF Research Database (Denmark)

    Sreedharan, V.; Hjertager, B.H.; Solberg, T.

    2010-01-01

    in reliability, emission control, efficiency, and feedstock flexibility. The feedstock used for a gasification system can be coal, petroleum coke, biomass, heavy oil, or even natural gas. This is an abstract of a paper presented at the 2010 AIChE Annual Meeting (Salt Lake City, UT 11/7-12/2010)....

  1. CFD Simulation of Entrained Flow Gasification With Improved Devolatilization and Char Consumption Submodels

    KAUST Repository

    Kumar, Mayank; Zhang, Cheng; Monaghan, Rory F. D.; Singer, Simcha L.; Ghoniem, Ahmed F.

    2009-01-01

    In this work, we use a CFD package to model the operation of a coal gasifier with the objective of assessing the impact of devolatilization and char consumption models on the accuracy of the results. Devolatilization is modeled using the Chemical Percolation Devolitilization (CPD) model. The traditional CPD models predict the rate and the amount of volatiles released but not their species composition. We show that the knowledge of devolatilization rates is not sufficient for the accurate prediction of char consumption and a quantitative description of the devolatilization products, including the chemical composition of the tar, is needed. We incorporate experimental data on devolatilization products combined with modeling of the tar composition and reactions to improve the prediction of syngas compositions and carbon conversion. We also apply the shrinking core model and the random pore model to describe char consumption in the CFD simulations. Analysis of the results indicates distinct regimes of kinetic and diffusion control depending on the particle radius and injection conditions for both char oxidation and gasification reactions. The random pore model with Langmuir-Hinshelwood reaction kinetics are found to be better at predicting carbon conversion and exit syngas composition than the shrinking core model with Arrhenius kinetics. In addition, we gain qualitative and quantitative insights into the impact of the ash layer surrounding the char particle on the reaction rate. Copyright © 2010 by ASME.

  2. Entrained Flow Reactor Study of K-Capture by Solid Additives

    DEFF Research Database (Denmark)

    Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao

    2016-01-01

    are collected from the cyclone and filter. The K-capture reaction is evaluated by determining the fraction of water-insoluble K in the products. The results showed that KCl can effectively be captured by kaolin and coal fly ash, forming water-insoluble K-aluminosilicates. The amount of K, captured per gram...

  3. Entraining the topology and the dynamics of a network of phase oscillators

    Science.gov (United States)

    Sendiña-Nadal, I.; Leyva, I.; Buldú, J. M.; Almendral, J. A.; Boccaletti, S.

    2009-04-01

    We show that the topology and dynamics of a network of unsynchronized Kuramoto oscillators can be simultaneously controlled by means of a forcing mechanism which yields a phase locking of the oscillators to that of an external pacemaker in connection with the reshaping of the network’s degree distribution. The entrainment mechanism is based on the addition, at regular time intervals, of unidirectional links from oscillators that follow the dynamics of a pacemaker to oscillators in the pristine graph whose phases hold a prescribed phase relationship. Such a dynamically based rule in the attachment process leads to the emergence of a power-law shape in the final degree distribution of the graph whenever the network is entrained to the dynamics of the pacemaker. We show that the arousal of a scale-free distribution in connection with the success of the entrainment process is a robust feature, characterizing different networks’ initial configurations and parameters.

  4. Toward better assessment of tornado potential in typhoons: Significance of considering entrainment effects for CAPE

    Science.gov (United States)

    Sueki, Kenta; Niino, Hiroshi

    2016-12-01

    The characteristics of typhoons that spawned tornadoes (tornadic typhoons: TTs) in Japan from 1991 to 2013 were investigated by composite analysis using the Japanese 55 year Reanalysis and compared with those of typhoons that did not spawn tornadoes (nontornadic typhoons: NTs). We found that convective available potential energy (CAPE), which considers the effects of entrainment (entraining CAPE: E-CAPE), and storm-relative environmental helicity (SREH) are significantly large in the northeast quadrant of TTs where tornadoes frequently occur and that E-CAPE and SREH in that quadrant for TTs are larger than those for NTs. On the other hand, ordinary CAPE without entrainment does not account for the spatial distribution of tornado occurrences nor does it distinguish TTs from NTs. E-CAPE is sensitive to humidity in the midtroposphere; thus, it is effective for detecting a conditionally unstable layer up to about 550 hPa, which is distinctive of TTs.

  5. The Importance of Stochastic Effects for Explaining Entrainment in the Zebrafish Circadian Clock

    Directory of Open Access Journals (Sweden)

    Raphaela Heussen

    2015-01-01

    Full Text Available The circadian clock plays a pivotal role in modulating physiological processes and has been implicated, either directly or indirectly, in a range of pathological states including cancer. Here we investigate how the circadian clock is entrained by external cues such as light. Working with zebrafish cell lines and combining light pulse experiments with simulation efforts focused on the role of synchronization effects, we find that even very modest doses of light exposure are sufficient to trigger some entrainment, whereby a higher light intensity or duration correlates with strength of the circadian signal. Moreover, we observe in the simulations that stochastic effects may be considered an essential feature of the circadian clock in order to explain the circadian signal decay in prolonged darkness, as well as light initiated resynchronization as a strong component of entrainment.

  6. Observational study of the relationship between entrainment rate and relative dispersion in deep convective clouds

    Science.gov (United States)

    Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; Liu, Yangang; Zhang, Guang Jun; Luo, Shi

    2018-01-01

    This study investigates the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found to be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.

  7. Reflooding phase of the LOCA in PWRs. Part II: rewetting and liquid entrainment

    International Nuclear Information System (INIS)

    Elias, E.; Yadigaroglu, G.

    1978-01-01

    Surface rewetting and liquid-droplet entrainment play an important role in the analysis of the reflooding phase of the loss-of-coolant accident in pressurized-water reactors. The definitions and the various interpretations given to the rewetting temperature and the rewetting mechanisms of the fuel rods are discussed. Published models of the axial-conduction-controlled rewetting process include one-dimensional solutions in two axial regions, one-dimensional solutions in three axial regions with or without precursory cooling, one- and two-dimensional numerical-difference techniques using temperature-dependent heat-transfer coefficients, and analytical two-dimensional solutions. The basic physical assumptions and the numerical values assigned to the various parameters, as well as empirical rewetting correlations, are discussed. The physical mechanisms for liquid-droplet entrainment and analytical formulations of the critical gas velocity and of the droplet diameter at the onset of entrainment are reviewed

  8. Laboratory experiments on the entrainment by a Concentrated Benthic Suspension

    NARCIS (Netherlands)

    Bruens, A.W.

    2000-01-01

    The deposition of cohesive sediments in estuarin and eoestal environments can lead to a range of managerial problems. To deal with these problems it is essential to understand the behaviour of cohesive sediment and its interaction with the flow field. During slack water, cohesive sediment is

  9. Entrainment and phase-shifting by centrifugation abolished in mice lacking functional vestibular input

    Science.gov (United States)

    Fuller, Charles; Ringgold, Kristyn

    The circadian pacemaker can be phase shifted and entrained by appropriately timed locomotor activity, however the mechanism(s) involved remain poorly understood. Recent work in our lab has suggested the involvement of the vestibular otolith organs in activity-induced changes within the circadian timing system (CTS). For example, we have shown that changes in circa-dian period and phase in response to locomotion (wheel running) require functional macular gravity receptors. We believe the neurovestibular system is responsible for the transduction of gravitoinertial input associated with the types of locomotor activity that are known to af-fect the pacemaker. This study investigated the hypothesis that daily, timed gravitoinertial stimuli, as applied by centrifugation. would induce entrainment of circadian rhythms in only those animals with functional afferent vestibular input. To test this hypothesis, , chemically labyrinthectomized (Labx) mice, mice lacking macular vestibular input (head tilt or hets) and wildtype (WT) littermates were implanted i.p. with biotelemetry and individually housed in a 4-meter diameter centrifuge in constant darkness (DD). After 2 weeks in DD, the mice were exposed daily to 2G via centrifugation from 1000-1200 for 9 weeks. Only WT mice showed entrainment to the daily 2G pulse. The 2G pulse was then re-set to occur at 1200-1400 for 4 weeks. Only WT mice demonstrated a phase shift in response to the re-setting of the 2G pulse and subsequent re-entrainment to the new centrifugation schedule. These results provide further evidence that gravitoinertial stimuli require a functional vestibular system to both en-train and phase shift the CTS. Entrainment among only WT mice supports the role of macular gravity receptive cells in modulation of the CTS while also providing a functional mechanism by which gravitoinertial stimuli, including locomotor activity, may affect the pacemaker.

  10. Is the food-entrainable circadian oscillator in the digestive system?

    Science.gov (United States)

    Davidson, A. J.; Poole, A. S.; Yamazaki, S.; Menaker, M.

    2003-01-01

    Food-anticipatory activity (FAA) is the increase in locomotion and core body temperature that precedes a daily scheduled meal. It is driven by a circadian oscillator but is independent of the suprachiasmatic nuclei. Recent results that reveal meal-entrained clock gene expression in rat and mouse peripheral organs raise the intriguing possibility that the digestive system is the site of the feeding-entrained oscillator (FEO) that underlies FAA. We tested this possibility by comparing FAA and Per1 rhythmicity in the digestive system of the Per1-luciferase transgenic rat. First, rats were entrained to daytime restricted feeding (RF, 10 days), then fed ad libitum (AL, 10 days), then food deprived (FD, 2 days). As expected FAA was evident during RF and disappeared during subsequent AL feeding, but returned at the correct phase during deprivation. The phase of Per1 in liver, stomach and colon shifted from a nocturnal to a diurnal peak during RF, but shifted back to nocturnal phase during the subsequent AL and remained nocturnal during food deprivation periods. Second, rats were entrained to two daily meals at zeitgeber time (ZT) 0400 and ZT 1600. FAA to both meals emerged after about 10days of dual RF. However, all tissues studied (all five liver lobes, esophagus, antral stomach, body of stomach, colon) showed entrainment consistent with only the night-time meal. These two results are inconsistent with the hypothesis that FAA arises as an output of rhythms in the gastrointestinal (GI) system. The results also highlight an interesting diversity among peripheral oscillators in their ability to entrain to meals and the direction of the phase shift after RF ends.

  11. Independence of circadian entrainment state and responses to melatonin in male Siberian hamsters

    Directory of Open Access Journals (Sweden)

    Gorman Michael R

    2003-10-01

    Full Text Available Abstract Background Seasonal fluctuations in physiology and behavior depend on the duration of nocturnal melatonin secretion programmed by the circadian system. A melatonin signal of a given duration, however, can elicit different responses depending on whether an animal was previously exposed to longer or shorter photoperiod signals (i.e., its photoperiodic history. This report examined in male Siberian hamsters which of two aspects of photoperiod history – prior melatonin exposure or entrainment state of the circadian system – is critical for generating contingent responses to a common photoperiodic signal. Results In Experiment #1, daily melatonin infusions of 5 or 10 h duration stimulated or inhibited gonadal growth, respectively, but had no effect on entrainment of the locomotor activity rhythm to long or short daylengths, thereby demonstrating that melatonin history and entrainment status could be experimentally dissociated. These manipulations were repeated in Experiment #2, and animals were subsequently exposed to a 12 week regimen of naturalistic melatonin signals shown in previous experiments to reveal photoperiodic history effects. Gonadal responses differed as a function of prior melatonin exposure but were unaffected by the circadian entrainment state. Experiment #3 demonstrated that a new photoperiodic history could be imparted during four weeks of exposure to long photoperiods. This effect, moreover, was blocked in animals treated concurrently with constant release melatonin capsules that obscured the endogenous melatonin signal: Following removal of the implants, the gonadal response depended not on the immediately antecedent circadian entrainment state, but on the more remote photoperiodic conditions prior to the melatonin implant. Conclusions The interpretation of photoperiodic signals as a function of prior conditions depends specifically on the history of melatonin exposure. The photoperiodic regulation of circadian

  12. Measurement of the rate of droplet deposition in vertical upward and downward annular flows

    International Nuclear Information System (INIS)

    Murakami, Toshihiro; Okawa, Tomio; Takei, Rei

    2008-01-01

    The deposition rate of droplets was measured for vertical annular two-phase flows in a small diameter tube by means of the double film extraction technique. The test section was a round tube of 5 mm in inside diameter, air and water were used as test fluids, and the flow direction was set to upward and downward; the system pressure and the flow rates of gas and liquid phases were changed parametrically. If the droplet velocity relative to the continuous gas phase is in the equilibrium state, the shear induced lift force acting on droplets is directed toward the tube centerline in upflow while toward the tube wall in downflow. Particular attention was therefore paid to the effect of flow direction. It was shown experimentally that the deposition rate of droplets in downward flow is greater than that in upward flow. The difference in the measured deposition rate may be attributed to the direction of lift force acting on droplets. (author)

  13. Physical and neural entrainment to rhythm: human sensorimotor coordination across tasks and effector systems

    Directory of Open Access Journals (Sweden)

    Jessica Marie Ross

    2014-08-01

    Full Text Available The human sensorimotor system can be readily entrained to environmental rhythms, through multiple sensory modalities. In this review, we provide an overview of theories of timekeeping that make this neuroentrainment possible. First, we present recent evidence that contests the assumptions made in classic timekeeper models. The role of state estimation, sensory feedback and movement parameters on the organization of sensorimotor timing are discussed in the context of recent experiments that examined simultaneous timing and force control. This discussion is extended to the study of coordinated multi-effector movements and how they may be entrained.

  14. Heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-Si alloys investigated by entrained droplet technique and DSC

    International Nuclear Information System (INIS)

    Li, J H; Schumacher, P; Albu, M; Hofer, F; Ludwig, T H; Arnberg, L

    2016-01-01

    Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed. This can be attributed to the formation of phosphide compounds having a lower free energy and hence may preferentially form compared to AlP. Only a trace P addition was found to have a profound effect on the nucleation process. The nucleation kinetics is discussed on the basis of the classical nucleation theory and the free growth model, respectively. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur within the droplets, which strongly indicates that the nucleation of Si on an AlP patch or AlP particle is a limiting step for free growth. The maximum nucleation site density within one droplet is directly related to the size distribution of AlP particles or AlP patches for Si nucleation, but is independent of the cooling rates. Although the nucleation conditions were optimized in entrained droplet experiments, the observed mechanisms are also valid at moderate cooling conditions, such as in shape casting. (paper)

  15. An Investigation into the Mechanics of Windblown Dust Entrainment from Nickel Slag Surfaces Resembling Armoured Desert Pavements

    Science.gov (United States)

    Sanderson, Robert Steven

    The purpose of this thesis is to investigate the dynamics of PM 10 emission from a nickel slag stockpile that closely resembles a desert pavement in physical characteristics. In the field, it was observed that slag surfaces develop by natural processes into a well-armoured surface over some period of time. The surface then consists of two distinct layers; a surficial armour layer containing only non-erodible gravel and cobble-sized clasts, and an underlying dust-laden layer, which contains a wide size range of slag particles, from clay-sized to cobble-sized. This surficial armour layer protects the underlying fines from wind entrainment, at least under typical wind conditions; however, particle emissions still do occur under high wind speeds. The dynamics of particle entrainment from within these surfaces are investigated herein. It is shown that the dynamics of the boundary layer flow over these lag surfaces are influenced by the inherent roughness and permeability of the surficial armour layer, such that the flow resembles those observed over and within vegetation canopies, and those associated with permeable gravel-bed river channels. Restriction of air flow within the permeable surface produces a high-pressure zone within the pore spaces, resulting in a Kelvin-Helmholtz shear instability, which triggers coherent motions in the form of repeating burst-sweep cycles. Using Laser Doppler Anemometry (LDA), it is demonstrated that the lower boundary layer is characterized by both Q4 sweeping motions and Q2 bursting motions, while the upper boundary layer is dominated by Q2 bursts. Pore air motions within the slag material were measured using buried pressure ports. It is shown that the mean pressure gradient which forms within the slag material results in net upward displacement of air, or wind pumping. However, this net upward motion is a result of rapid oscillatory motions which are directly driven by coherent boundary layer motions. It is also demonstrated that

  16. Standard for prevention of gas entrainment phenomena in fast reactors. (1) Validations of CFD methods for reproducibilities of gas entrainment phenomena; 高速炉におけるガス巻込み現象の防止基準. (1) 数値解析によるガス巻込み現象再現精度の検証

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, Hiroyuki; Uchibori, Akihiro; Ito, Kei; Sakai, Takaaki [Japan Atomic Energy Agency, Advanced Nuclear System Research and Development Directorate, Oarai, Ibaraki (Japan); Tanaka, Nobuatsu [Ibaraki University, Department of Mechanical Engineering, Hitachi, Ibaraki (Japan); Eguchi, Yuzuru [Central Research Institute of Electric Power Industry (CRIEPI), Civil Engineering Research Laboratory, Abiko, Chiba (Japan); Nishimura, Motohiko [Kawasaki Heavy Industries, Ltd., Technical Institute, Akashi, Hyogo (Japan); Kunugi, Tomoaki [Kyoto Univ., Department of Nuclear Engineering, Kyoto, Kyoto (Japan)

    2012-12-15

    It is of importance for stable operations of sodium-cooled fast reactors (SFRs) to prevent gas entrainment (GE) phenomena due to free surface vortices. The entrained gas flow rate should be below an allowance level. However, theoretical determination of universal onset conditions of GE is difficult due to nonlinear characteristics of GE phenomena. Therefore, the authors have been developing an evaluation method for GE based on computational fluid dynamics (CFD) methods. In this study, we determine a suitable CFD method for GE phenomena from several candidates through some numerical benchmarks. As a result, we obtain the following guideline for the vortex-induced gas entrainment. The free vortex flow around the vortex core can be correctly evaluated by using appropriate numerical models, such as sufficient mesh resolution, suitable advection solver, suitable turbulence and free surface modeling. From the geometrical viewpoint, the jagged description of the curved boundary using a rectangular mesh is not suitable since it damps rotating flow. As for turbulence modeling, which is especially investigated in this paper, direct numerical simulation (DNS) without any turbulent model is strongly recommended, but RNG k-ε and LES are acceptable. Lastly, we apply the recommended methods to the numerical analysis of a large-scale (>1/2) test experiment. The numerical results show good agreement with the onset condition of the GE observed in the experiments. This fact indicates that our recommended CFD methods are applicable to the GE phenomena in SFRs. In the next paper, a GE evaluation method is developed, which can calculate GE occurrences based on the results of numerical simulations performed in accordance with the simulation guideline proposed in this paper. (author)

  17. 76 FR 6328 - Official Release of the January 2011 AP-42 Method for Estimating Re-Entrained Road Dust From...

    Science.gov (United States)

    2011-02-04

    ... Nonattainment and Maintenance Areas'' (EPA-420-B-10-040, December 2010). \\2\\ For estimating road dust from... maintenance areas and any PM 2.5 nonattainment and maintenance areas where re-entrained road dust is a... January 2011 AP-42 Method for Estimating Re-Entrained Road Dust From Paved Roads AGENCY: Environmental...

  18. A CFD Investigation on the Effect of the Air Entrainment in Breaking Wave Impacts on a Mono-Pile

    DEFF Research Database (Denmark)

    Tomaselli, Pietro; Christensen, Erik Damgaard

    2017-01-01

    In impacts of breaking waves on offshore structures, it is still not well-known how the air entrainment phenomenon affects the exerted loads. In this paper, a developed CFD solver capable of simulating the air entrainment process was employed to repro-duce an experimental investigation on the imp......In impacts of breaking waves on offshore structures, it is still not well-known how the air entrainment phenomenon affects the exerted loads. In this paper, a developed CFD solver capable of simulating the air entrainment process was employed to repro-duce an experimental investigation...... on the impact of a spilling wave against a circular cylinder. The exerted in-line force was computed with and without the inclusion of dispersed bubbles. Results showed that the magnitude of the computed force was affected when the entrainment of bubbles was simulated....

  19. Historical review of entrainment impact estimates and the factors influencing them

    International Nuclear Information System (INIS)

    Englert, T.L.; Boreman, J.

    1988-01-01

    Estimates of entrainment mortality have played a key role in the Hudson River power plant case since the late 1960s. The estimates of entrainment mortality of striped bass due to the operation of Indian Point nuclear plant were first presented by utility and government consultants in 1972. These estimates were derived with the first of many generations of mathematical models. Assumed values had to be used for some of the critical parameters because of the limited amount of data available. The government estimates were much higher as a result of the intentional use of conservative assumptions. As more data became available and model formulations evolved, fewer assumptions were needed, the government estimates declined, and the gap between estimates from the two groups of consultants narrowed markedly. Several factors contributed to the convergence of model estimates, but a key factor was field data showing that more than half of the entrained striped bass survive passage through the plant. The convergence of estimates of entrainment mortality was a key ingredient in the eventual formulation of the settlement agreement and showed that progress had been made in resolving an important portion of the heavily contested issues. 18 refs., 2 figs., 1 tab

  20. The influence of nitrogen entrainment on argon plasmas created by the 'Torche à Injection Axiale' (TIA)

    NARCIS (Netherlands)

    Jonkers, J.; Hartgers, A.; Selen, L.J.M.; Mullen, van der J.J.A.M.; Schram, D.C.

    1999-01-01

    When a plasma is sustained in the open air, nitrogen will diffuse into the plasma. Especially for plasmas sustained by the `Torche à Injection Axiale' (TIA) this appears to be the case, since this turbulent jet draws gases from the surroundings. In the argon plasma the entrained nitrogen is probably

  1. Entrainer-based reactive distillation versus conventional reactive distillation for the synthesis of fatty acid esters

    NARCIS (Netherlands)

    Jong, de M.C.; Dimian, A.C.; Haan, de A.B.

    2008-01-01

    In this paper different reactive distillation configurations for the synthesis of isopropyl myristate were compared with the use of process models made in Aspen Plus. It can be concluded that the configurations in which an entrainer is added are more capable to reach the required conversion of

  2. Influences of the chemical structure of entrainers on the activity coefficients in presence of biodiesel

    International Nuclear Information System (INIS)

    Mäder, A; Fleischmann, A; Fang, Ye; Krahl, J; Ruck, W

    2012-01-01

    In this work we analyzed the strength of the intermolecular forces between biodiesel and the entrainer and their influence on the entrainer's ability to interact with biodiesel. Furthermore we investigated the influence of the chemical structure of an entrainer to the interaction with biodiesel. For this purpose the activity coefficients γ ∞ at infinite dilution of acids, aldehydes, ketones and alcohols in biodiesel were measured with the method of headspace gas chromatography (HSGC). Short-chained acids showed the highest interaction of the analyzed entrainers caused by their ability to build hydrogen bonds with biodiesel. Increased chain length of the acids cause reduced interaction with biodiesel, which is mainly due to the higher obstruction of the acid molecule and therefore the reduced ability to build hydrogen bonds with biodiesel. Aldehydes, ketones and alcohols showed lower interaction with biodiesel compared to the acids. Longer-chained alcohols showed increased interaction with biodiesel due to the raised London Forces and an inductive +I effect of the molecule chain.

  3. Evaluation by entrained imaging of the positioning precision and repositioning in fractionated stereotaxic radiotherapy

    International Nuclear Information System (INIS)

    Brunet, G.; Delpon, G.; Bardet, E.; Bourdin, S.; Gaudaire, S.; Munos, C.; Preuvel, P.; Mahe, M.A.; Lisbona, A.

    2006-01-01

    The differences of daily positioning have been quantified and the precision of this king of contention has been evaluated. The buccal support improves the positioning precision. The daily use of the entrained image is feasible in routine and allows a measurable improvement of the treatment precision. (N.C.)

  4. Demasking biological oscillators : Properties and principles of entrainment exemplified by the Neurospora circadian clock

    NARCIS (Netherlands)

    Roenneberg, T; Dragovic, Z; Merrow, M; Takahashi, Joseph S.

    2005-01-01

    Oscillations are found throughout the physical and biological worlds. Their interactions can result in a systematic process of synchronization called entrainment, which is distinct from a simple stimulus-response pattern. Oscillators respond to stimuli at some times in their cycle and may not

  5. Physics of Particle Entrainment Under the Influence of an Impinging Jet

    Science.gov (United States)

    2008-12-01

    Approved for public release; distribution unlimited 1 PHYSICS OF PARTICLE ENTRAINMENT UNDER THE INFLUENCE OF AN IMPINGING JET Robert Haehnel...Ing. Wesen. Heft 361). Phares, D.J., Smedley , G.T. and Flagan, R.C. (2000) "The wall shear stress produced by the normal impingement of a jet on a

  6. Influence of photoperiod and running wheel access on the entrainment of split circadian rhythms in hamsters

    Directory of Open Access Journals (Sweden)

    Elliott Jeffrey A

    2005-06-01

    Full Text Available Abstract Background In the laboratory, behavioral and physiological states of nocturnal rodents alternate, with a period near 24 h, between those appropriate for the night (e.g., elevated wheel-running activity and high melatonin secretion and for the day (e.g., rest and low melatonin secretion. Under appropriate 24 h light:dark:light:dark conditions, however, rodents may be readily induced to express bimodal rest/activity cycles that reflect a global temporal reorganization of the central neural pacemaker in the hypothalamus. We examine here how the relative length of the light and dark phases of the environmental cycle influences this rhythm splitting and the necessity of a running wheel for expression of this entrainment condition. Results Rhythm splitting was observed in wheel-running and general locomotion of Siberian and Syrian hamsters. The latter also manifest split rhythms in body temperature. Access to a running wheel was necessary neither for the induction nor maintenance of this entrainment pattern. While rhythms were only transiently split in many animals with two 5 h nights, the incidence of splitting was greater with twice daily nights of shorter duration. Removal of running wheels altered the body temperature rhythm but did not eliminate its clear bimodality. Conclusion The expression of entrained, split circadian rhythms exhibits no strict dependence on access to a running wheel, but can be facilitated by manipulation of ambient lighting conditions. These circadian entrainment patterns may be of therapeutic value to human shift-workers and others facing chronobiological challenges.

  7. Novel non-indolic melatonin receptor agonists differentially entrain endogenous melatonin rhythm and increase its amplitude

    NARCIS (Netherlands)

    Drijfhout, W.J; de Vries, J.B; Homan, E.J; Brons, H.F; Copinga, S; Gruppen, G; Beresford, I.J M; Hagan, R.M; Grol, Cor; Westerink, B.H.C.

    1999-01-01

    In this study we have examined the ability of melatonin and four synthetic melatonin receptor agonists to entrain endogenous melatonin secretion in rats, free running in constant darkness. The circadian melatonin profile was measured by trans-pineal microdialysis, which not only reveals the time of

  8. A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents. IV. Entrainment : Pacemaker as Clock

    NARCIS (Netherlands)

    Pittendrigh, Colin S.; Daan, Serge

    1976-01-01

    1. In the first part of the paper, the model of non-parametric entrainment of circadian pacemakers is tested for the case of nocturnal rodents. The model makes use of the available data on freerunning period (τ) in constant darkness and on phase response curves (PRC) for short light pulses. It is

  9. CONCEPTUAL DESIGN OF NON-IDEAL MIXTURE SEPARATION WITH LIGHT ENTRAINERS

    Directory of Open Access Journals (Sweden)

    W. Shen

    Full Text Available Abstract A method is proposed to study the separation of minimum-, maximum-boiling azeotropic, and low volatility mixtures with a light entrainer, to investigate feasible regions of the key operating parameters reboil ratio (S and entrainer - feed flowrate ratio (FE/F for continuous processes. The thermodynamic topological predictions are carried out for 1.0-2, 1.0-1a, and 0.0-1 Serafimov's class diagrams. It relies upon the knowledge of residue curve maps, along with the univolatility line, and it enables the prediction of possible products at the bottom of the column and limiting values of FE/F. The profiles of the stripping, extractive, and rectifying sections are calculated by equations considering S and FE/F, and they bring information about the location of singular points and possible composition profile separatrices that could impair process feasibility. Providing specified product composition and recovery, the approximate calculations are compared with rigorous simulations of extractive distillation processes. Separating non-ideal mixtures using a light entrainer provides more opportunities for the case when it is not easy to find an appropriate heavy or intermediate entrainer.

  10. Fish Oil Accelerates Diet-Induced Entrainment of the Mouse Peripheral Clock via GPR120

    Science.gov (United States)

    Itokawa, Misa; Nagahama, Hiroki; Ohtsu, Teiji; Furutani, Naoki; Kamagata, Mayo; Yang, Zhi-Hong; Hirasawa, Akira; Tahara, Yu; Shibata, Shigenobu

    2015-01-01

    The circadian peripheral clock is entrained by restricted feeding (RF) at a fixed time of day, and insulin secretion regulates RF-induced entrainment of the peripheral clock in mice. Thus, carbohydrate-rich food may be ideal for facilitating RF-induced entrainment, although the role of dietary oils in insulin secretion and RF-induced entrainment has not been described. The soybean oil component of standard mouse chow was substituted with fish or soybean oil containing docosahexaenoic acid (DHA) and/or eicosapentaenoic acid (EPA). Tuna oil (high DHA/EPA), menhaden oil (standard), and DHA/EPA dissolved in soybean oil increased insulin secretion and facilitated RF-induced phase shifts of the liver clock as represented by the bioluminescence rhythms of PER2::LUCIFERASE knock-in mice. In this model, insulin depletion blocked the effect of tuna oil and fish oil had no effect on mice deficient for GPR120, a polyunsaturated fatty acid receptor. These results suggest food containing fish oil or DHA/EPA is ideal for adjusting the peripheral clock. PMID:26161796

  11. Gas entrainment by one single French PWR spray, SARNET-2 spray benchmark

    Energy Technology Data Exchange (ETDEWEB)

    Malet, J., E-mail: jeanne.malet@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, Saclay (France); Mimouni, S., E-mail: stephane.mimouni@edf.fr [Electricité de France, EDF MF2E, Chatou (France); Manzini, G., E-mail: giovanni.manzini@rse-web.it [RSE, Milano (Italy); Xiao, J., E-mail: jianjun.xiao@kit.edu [IKET, KIT, Karlsruhe (Germany); Vyskocil, L., E-mail: vyl@ujv.cz [UJV Rez (Czech Republic); Siccama, N.B., E-mail: siccama@nrg.eu [NRG, Safety and Power (Netherlands); Huhtanen, R., E-mail: risto.huhtanen@vtt.fi [VTT, PO Box 1000, FI-02044 VTT (Finland)

    2015-02-15

    Highlights: • This paper presents a benchmark performed in the frame of the SARNET-2 EU project. • It concerns momentum transfer between a PWR spray and the surrounding gas. • The entrained gas velocities can vary up to 100% from one code to another. • Simplified boundary conditions for sprays are generally used by the code users. • It is shown how these simplified conditions impact the gas entrainment. - Abstract: This paper presents a benchmark performed in the frame of the SARNET-2 EU project, dealing with momentum transfer between a real-scale PWR spray and the surrounding gas. It presents a description of the IRSN tests on the CALIST facility, the participating codes (8 contributions), code-experiment and code-to-code comparisons. It is found that droplet velocities are almost well calculated one meter below the spray nozzle, even if the spread of the spray is not recovered and the values of the entrained gas velocity vary up to 100% from one code to another. Concerning sensitivity analysis, several ‘simplifications’ have been made by the contributors, especially based on the boundary conditions applied at the location where droplets are injected. It is shown here that such simplifications influence droplet and entrained gas characteristics. The next step will be to translate these conclusions in terms of variables representative of interesting parameters for nuclear safety.

  12. Gas entrainment by one single French PWR spray, SARNET-2 spray benchmark

    International Nuclear Information System (INIS)

    Malet, J.; Mimouni, S.; Manzini, G.; Xiao, J.; Vyskocil, L.; Siccama, N.B.; Huhtanen, R.

    2015-01-01

    Highlights: • This paper presents a benchmark performed in the frame of the SARNET-2 EU project. • It concerns momentum transfer between a PWR spray and the surrounding gas. • The entrained gas velocities can vary up to 100% from one code to another. • Simplified boundary conditions for sprays are generally used by the code users. • It is shown how these simplified conditions impact the gas entrainment. - Abstract: This paper presents a benchmark performed in the frame of the SARNET-2 EU project, dealing with momentum transfer between a real-scale PWR spray and the surrounding gas. It presents a description of the IRSN tests on the CALIST facility, the participating codes (8 contributions), code-experiment and code-to-code comparisons. It is found that droplet velocities are almost well calculated one meter below the spray nozzle, even if the spread of the spray is not recovered and the values of the entrained gas velocity vary up to 100% from one code to another. Concerning sensitivity analysis, several ‘simplifications’ have been made by the contributors, especially based on the boundary conditions applied at the location where droplets are injected. It is shown here that such simplifications influence droplet and entrained gas characteristics. The next step will be to translate these conclusions in terms of variables representative of interesting parameters for nuclear safety

  13. Speech entrainment enables patients with Broca’s aphasia to produce fluent speech

    Science.gov (United States)

    Hubbard, H. Isabel; Hudspeth, Sarah Grace; Holland, Audrey L.; Bonilha, Leonardo; Fromm, Davida; Rorden, Chris

    2012-01-01

    A distinguishing feature of Broca’s aphasia is non-fluent halting speech typically involving one to three words per utterance. Yet, despite such profound impairments, some patients can mimic audio-visual speech stimuli enabling them to produce fluent speech in real time. We call this effect ‘speech entrainment’ and reveal its neural mechanism as well as explore its usefulness as a treatment for speech production in Broca’s aphasia. In Experiment 1, 13 patients with Broca’s aphasia were tested in three conditions: (i) speech entrainment with audio-visual feedback where they attempted to mimic a speaker whose mouth was seen on an iPod screen; (ii) speech entrainment with audio-only feedback where patients mimicked heard speech; and (iii) spontaneous speech where patients spoke freely about assigned topics. The patients produced a greater variety of words using audio-visual feedback compared with audio-only feedback and spontaneous speech. No difference was found between audio-only feedback and spontaneous speech. In Experiment 2, 10 of the 13 patients included in Experiment 1 and 20 control subjects underwent functional magnetic resonance imaging to determine the neural mechanism that supports speech entrainment. Group results with patients and controls revealed greater bilateral cortical activation for speech produced during speech entrainment compared with spontaneous speech at the junction of the anterior insula and Brodmann area 47, in Brodmann area 37, and unilaterally in the left middle temporal gyrus and the dorsal portion of Broca’s area. Probabilistic white matter tracts constructed for these regions in the normal subjects revealed a structural network connected via the corpus callosum and ventral fibres through the extreme capsule. Unilateral areas were connected via the arcuate fasciculus. In Experiment 3, all patients included in Experiment 1 participated in a 6-week treatment phase using speech entrainment to improve speech production

  14. Cortical oscillations and entrainment in speech processing during working memory load.

    Science.gov (United States)

    Hjortkjaer, Jens; Märcher-Rørsted, Jonatan; Fuglsang, Søren A; Dau, Torsten

    2018-02-02

    Neuronal oscillations are thought to play an important role in working memory (WM) and speech processing. Listening to speech in real-life situations is often cognitively demanding but it is unknown whether WM load influences how auditory cortical activity synchronizes to speech features. Here, we developed an auditory n-back paradigm to investigate cortical entrainment to speech envelope fluctuations under different degrees of WM load. We measured the electroencephalogram, pupil dilations and behavioural performance from 22 subjects listening to continuous speech with an embedded n-back task. The speech stimuli consisted of long spoken number sequences created to match natural speech in terms of sentence intonation, syllabic rate and phonetic content. To burden different WM functions during speech processing, listeners performed an n-back task on the speech sequences in different levels of background noise. Increasing WM load at higher n-back levels was associated with a decrease in posterior alpha power as well as increased pupil dilations. Frontal theta power increased at the start of the trial and increased additionally with higher n-back level. The observed alpha-theta power changes are consistent with visual n-back paradigms suggesting general oscillatory correlates of WM processing load. Speech entrainment was measured as a linear mapping between the envelope of the speech signal and low-frequency cortical activity (level) decreased cortical speech envelope entrainment. Although entrainment persisted under high load, our results suggest a top-down influence of WM processing on cortical speech entrainment. © 2018 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  15. Determination of maximum reactor power level consistent with the requirement that flow reversal occurs without fuel damage

    International Nuclear Information System (INIS)

    Rao, D.V.; Darby, J.L.; Ross, S.B.; Clark, R.A.

    1990-01-01

    The High Flux Beam Reactor (HFBR) operated by Brookhaven National Laboratory (BNL) employs forced downflow for heat removal during normal operation. In the event of total loss of forced flow, the reactor will shutdown and the flow reversal valves open. When the downward core flow becomes sufficiently small then the opposing thermal buoyancy induces flow reversal leading to decay heat removal by natural convection. There is some uncertainty as to whether the natural circulation is adequate for decay heat removal after 60 MW operation. BNL- staff carried out a series of calculations to establish the adequacy of flow reversal to remove decay heat. Their calculations are based on a natural convective CHF model. The primary purpose of the present calculations is to review the accuracy and applicability of Fauske's CHF model for the HFBR, and the assumptions and methodology employed by BNL-staff to determine the heat removal limit in the HFBR during a flow reversal and natural convection situation

  16. New insights into the wind-dust relationship in sandblasting and direct aerodynamic entrainment from wind tunnel experiments

    KAUST Repository

    Parajuli, Sagar Prasad; Zobeck, Ted M.; Kocurek, Gary; Yang, Zong-Liang; Stenchikov, Georgiy L.

    2016-01-01

    Numerous parameterizations have been developed for predicting wind erosion, yet the physical mechanism of dust emission is not fully understood. Sandblasting is thought to be the primary mechanism, but recent studies suggest that dust emission by direct aerodynamic entrainment can be significant under certain conditions. In this work, using wind tunnel experiments, we investigated some of the lesser understood aspects of dust emission in sandblasting and aerodynamic entrainment for three soil types, namely clay, silty clay loam, and clay loam. First, we explored the role of erodible surface roughness on dust emitted by aerodynamic entrainment. Second, we compared the emitted dust concentration in sandblasting and aerodynamic entrainment under a range of wind friction velocities. Finally, we explored the sensitivity of emitted dust particle size distribution (PSD) to soil type and wind friction velocity in these two processes. The dust concentration in aerodynamic entrainment showed strong positive correlation, no significant correlation, and weak negative correlation, for the clay, silty clay loam, and clay loam, respectively, with the erodible soil surface roughness. The dust in aerodynamic entrainment was significant constituting up to 28.3, 41.4, and 146.4% compared to sandblasting for the clay, silty clay loam, and clay loam, respectively. PSD of emitted dust was sensitive to soil type in both sandblasting and aerodynamic entrainment. PSD was sensitive to the friction velocity in aerodynamic entrainment but not in sandblasting. Our results highlight the need to consider the details of sandblasting and direct aerodynamic entrainment processes in parameterizing dust emission in global/regional climate models.

  17. New insights into the wind-dust relationship in sandblasting and direct aerodynamic entrainment from wind tunnel experiments

    KAUST Repository

    Parajuli, Sagar Prasad

    2016-01-22

    Numerous parameterizations have been developed for predicting wind erosion, yet the physical mechanism of dust emission is not fully understood. Sandblasting is thought to be the primary mechanism, but recent studies suggest that dust emission by direct aerodynamic entrainment can be significant under certain conditions. In this work, using wind tunnel experiments, we investigated some of the lesser understood aspects of dust emission in sandblasting and aerodynamic entrainment for three soil types, namely clay, silty clay loam, and clay loam. First, we explored the role of erodible surface roughness on dust emitted by aerodynamic entrainment. Second, we compared the emitted dust concentration in sandblasting and aerodynamic entrainment under a range of wind friction velocities. Finally, we explored the sensitivity of emitted dust particle size distribution (PSD) to soil type and wind friction velocity in these two processes. The dust concentration in aerodynamic entrainment showed strong positive correlation, no significant correlation, and weak negative correlation, for the clay, silty clay loam, and clay loam, respectively, with the erodible soil surface roughness. The dust in aerodynamic entrainment was significant constituting up to 28.3, 41.4, and 146.4% compared to sandblasting for the clay, silty clay loam, and clay loam, respectively. PSD of emitted dust was sensitive to soil type in both sandblasting and aerodynamic entrainment. PSD was sensitive to the friction velocity in aerodynamic entrainment but not in sandblasting. Our results highlight the need to consider the details of sandblasting and direct aerodynamic entrainment processes in parameterizing dust emission in global/regional climate models.

  18. A balanced diet is necessary for proper entrainment signals of the mouse liver clock.

    Directory of Open Access Journals (Sweden)

    Akiko Hirao

    Full Text Available BACKGROUND: The peripheral circadian clock in mice is entrained not only by light-dark cycles but also by daily restricted feeding schedules. Behavioral and cell culture experiments suggest an increase in glucose level as a factor in such feeding-induced entrainment. For application of feeding-induced entrainment in humans, nutrient content and dietary variations should be considered. PRINCIPAL FINDING: To elucidate the food composition necessary for dietary entrainment, we examined whether complete or partial substitution of dietary nutrients affected phase shifts in liver clocks of mice. Compared with fasting mice or ad libitum fed mice, the liver bioluminescence rhythm advanced by 3-4 h on the middle day in Per2::luciferase knock-in mice that were administered a standard mouse diet, i.e. AIN-93M formula [0.6-0.85 g/10 g mouse BW] (composition: 14% casein, 47% cornstarch, 15% gelatinized cornstarch, 10% sugar, 4% soybean oil, and 10% other [fiber, vitamins, minerals, etc.], for 2 days. When each nutrient was tested alone (100% nutrient, an insignificant weak phase advance was found to be induced by cornstarch and soybean oil, but almost no phase advance was induced by gelatinized cornstarch, high-amylose cornstarch, glucose, sucrose, or casein. A combination of glucose and casein without oil, vitamin, or fiber caused a significant phase advance. When cornstarch in AIN-93M was substituted with glucose, sucrose, fructose, polydextrose, high-amylose cornstarch, or gelatinized cornstarch, the amplitude of phase advance paralleled the increase in blood glucose concentration. CONCLUSIONS: Our results strongly suggest the following: (1 balanced diets containing carbohydrates/sugars and proteins are good for restricted feeding-induced entrainment of the peripheral circadian clock and (2 a balanced diet that increases blood glucose, but not by sugar alone, is suitable for entrainment. These findings may assist in the development of dietary

  19. Demonstration of Entrained Solids and Sr/TRU Removal Processes with Archived AN-107 Waste

    International Nuclear Information System (INIS)

    Hallen, R.T.; Brooks, K.P.; Jagoda, L.K.

    2000-01-01

    Archived AN-107 waste was used to evaluate entrained solids removal, Sr/TRU decontamination of supernatant, and Sr/TRU solids removal. Even though most of the entrained solids had been previously removed from the archived sample, the residual entrained solids rapidly fouled the filter element resulting in very poor filter performance. An attempt to run at higher pressure resulted in more fouling, and reduced filter performance. Filtration efforts to remove entrained solids were abandoned and the waste was treated for Sr/TRU removal with the entrained solids present. The new processing scheme for Sr/TRU removal involving precipitation by added strontium and permanganate worked well. The decontamination factors for Sr and TRU components were significantly greater than the ILAW DF requirements for higher reagent concentrations of 1M hydroxide, 0.075M Sr, and 0.05M permanganate and lower reagent concentrations of 0.8M hydroxide, 0.05M Sr, and 0.03M permanganate. These results support the use of lower concentration of reagent additions in future tests. Optimization studies should be conducted to examine the reduction in added hydroxide from 1M to 0.5 M, reduction of Sr from 0.075M to 0.05M, and reduction in permanganate from 0.05M to 0.03M and the impact this reduction has on filtration performance with new samples from Tank AN-107. The combined entrained solids and Sr/TRU precipitate were successfully filtered in the single element, crossflow filtration unit. The filtrate flux was high, >0.1 gpm/ft 2 , at the initial test conditions of 53 psi and 11.2ft/s for the treated archived AN-107 sample. The filter flux rate dropped significantly with time as testing progressed and appears to be a result of shearing the agglomerated solids and fouling of the filter element by the resulting fine particles. The relatively low clean water flux rates obtained at the end of the test also indicate filter fouling. Chemical cleaning was required to restore clean water flux rates to pre

  20. Fluidization mechanisms in slurry flow

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C. S.

    1989-01-01

    There are two mechanisms by which heavy settling particles may be suspended in a horizontal slurry flow: (1) by particle-particle interactions (e.g. Bagnold dispersive stresses) and (2) by particle-fluid interactions (e.g. entrainment of the particles by turbulent eddies.) The purpose of this investigation is to determine to what extent each fluidization mechanism is active and the effect of the fluidization mechanism on the global properties of the slurry. The technique employs the understanding that the particles entrained in the turbulence of the fluid will appear as an increased hydrostatic head across the channel. This may be directly measured and can be related to the fraction of the mass of particles that are supported by fluid-particle forces. (The rest must therefore be supported by particle-particle forces.) 17 refs., 26 figs.

  1. Dungeness Crab Dredging Entrainment Studies in the Lower Columbia River, 2002 – 2004: Loss Projections, Salinity Model, and Scenario Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, Walter H.; Williams, Greg D.; Skalski, John R.

    2005-01-01

    Dungeness crab studies conducted in 2002 for the Portland District of the U.S. Army Corps of Engineers (Corps) constituted a major step forward in quantifying crab entrainment through statistical projections of adult equivalent loss (AEL) and loss to the fishery (LF) from proposed construction and maintenance dredging in the Columbia River navigation channel (Pearson et al. 2002, 2003). These studies also examined the influence of bottom salinity on crab abundance and entrainment rates. Additional sampling was conducted in 2004 to tighten loss projections, further develop the crab salinity model, and apply the model to assess correlations of entrainment rates and projected losses with seasonal salinity changes.

  2. Azeotropic behaviour of (benzene + cyclohexane + chlorobenzene) ternary mixture using chlorobenzene as entrainer at 101.3 kPa

    International Nuclear Information System (INIS)

    Silva, L.M.C.; Mattedi, S.; Gonzalez-Olmos, R.; Iglesias, M.

    2006-01-01

    In this paper, the azeotropic behaviour of the (benzene + cyclohexane + chlorobenzene) ternary mixture was experimentally investigated with the aim of enhancing the knowledge for the feasible use of chlorobenzene as an entrainer for the azeotropic distillation of the binary azeotrope. Such a study has not been reported in the literature to the best of the authors' knowledge. (Vapour + liquid) equilibria data for (benzene + cyclohexane + chlorobenzene) at 101.3 kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits an unique binary homogeneous azeotrope, an unstable node at the conditions studied, and the propitious topological characteristics (residual curve map and relative volatility) to be separated. Satisfactory results were obtained for the correlation of equilibrium compositions with the UNIQUAC activity coefficients model and also for prediction with the UNIFAC method. In both cases, low root mean square deviations of the vapour mole fraction and temperature were calculated. The capability of chlorobenzene as a modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. A conceptual distillation scheme with reversed volatility is proposed to separate the azeotropic mixture. In order to reduce the operational cost requirements of the sequence of columns proposed, the range for optimal reflux and the ratio for feed flow conditions were studied

  3. Effect of Colombian coal rank and its feeding technology on substitute natural gas production by entrained gasification

    Directory of Open Access Journals (Sweden)

    Juan Fernando Pérez-Bayer

    2016-01-01

    Full Text Available The effect of coal rank (from sub-bituminous to semi-anthracite and type of fuel feeding technology (slurry and dry on the production of substitute natural gas (SNG in entrained flow gasifiers is studied. Ten coals from important Colombian mines were selected. The process is modeled under thermochemical equilibrium using Aspen Plus, and its performance is evaluated in function of output parameters that include SNG heating value, Wobbe index, coal conversion efficiency, cold gas efficiency, process efficiency, global efficiency, and SNG production rate, among others. In descending order, the coal-to-SNG process improves energetically with the use of coals with: higher volatile-matter to fixed-carbon ratio, lower ash content, higher C+H/O ratio, and higher coal heating value. The overall energy efficiency of the slurry-feed technology (S-FT to produce SNG by gasification is 17% higher than the dry-feed technology (D-FT, possibly as a consequence of the higher CH4 concentration in the syngas (around 7 vol. % when the coal is fed as aqueous slurry. As the simulated SNG meets the natural gas (NG quality standards in Colombia, the substitute gaseous fuel could be directly transported through pipelines. Therefore, the coal-to-SNG process is a technically feasible and unconventional alternative for NG production.

  4. Azeotropic behaviour of (benzene + cyclohexane + chlorobenzene) ternary mixture using chlorobenzene as entrainer at 101.3 kPa

    Energy Technology Data Exchange (ETDEWEB)

    Silva, L.M.C. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade Federal da Bahia, 40210 Salvador de Bahia (Brazil); Mattedi, S. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade Federal da Bahia, 40210 Salvador de Bahia (Brazil); Gonzalez-Olmos, R. [Departament d' Enginyeria Quimica, Escola Tecnica Superior d' Enginyeria Quimica, Universitat Rovira i Virgili, Avinguda Paisos Catalans 26, Campus Sescelades, 43007 Tarragona (Spain); Iglesias, M. [Departament d' Enginyeria Quimica, Escola Tecnica Superior d' Enginyeria Quimica, Universitat Rovira i Virgili, Avinguda Paisos Catalans 26, Campus Sescelades, 43007 Tarragona (Spain)]. E-mail: miguelangel.iglesias@urv.net

    2006-12-15

    In this paper, the azeotropic behaviour of the (benzene + cyclohexane + chlorobenzene) ternary mixture was experimentally investigated with the aim of enhancing the knowledge for the feasible use of chlorobenzene as an entrainer for the azeotropic distillation of the binary azeotrope. Such a study has not been reported in the literature to the best of the authors' knowledge. (Vapour + liquid) equilibria data for (benzene + cyclohexane + chlorobenzene) at 101.3 kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits an unique binary homogeneous azeotrope, an unstable node at the conditions studied, and the propitious topological characteristics (residual curve map and relative volatility) to be separated. Satisfactory results were obtained for the correlation of equilibrium compositions with the UNIQUAC activity coefficients model and also for prediction with the UNIFAC method. In both cases, low root mean square deviations of the vapour mole fraction and temperature were calculated. The capability of chlorobenzene as a modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. A conceptual distillation scheme with reversed volatility is proposed to separate the azeotropic mixture. In order to reduce the operational cost requirements of the sequence of columns proposed, the range for optimal reflux and the ratio for feed flow conditions were studied.

  5. Numerical study of the bubbly flow regime in micro-channel flow boiling

    Science.gov (United States)

    Bhuvankar, Pramod; Dabiri, Sadegh

    2017-11-01

    Two-phase flow accompanied by boiling in micro-channel heat sinks is an effective means for heat removal from computer chips. We present a numerical study of flow boiling in micro-channels with conjugate heat transfer with a focus on the bubbly flow regime. The bubbles are assumed to nucleate at a pre-determined location and frequency. The Navier Stokes equations are solved using a single fluid formulation with the Front tracking method. Phase change is implemented using the deficit in heat flux across the bubble interface. The analytical solution for bubble growth in a superheated liquid is used as a benchmark to validate the mentioned numerical method. Water and FC-72 are studied as the operating fluids in a micro-channel made of Copper with a focus on hotspot mitigation. The micro-channel of cross-section 231 μm × 1000 μm , is used to study the effects of vertical up-flow, vertical down-flow and horizontal flow of the mentioned fluids on the heat transfer coefficients. A simple film model accounting for mass and energy conservation is applied wherever the bubble approaches closer than a cell width to the wall. The results of the simulation are compared with existing experimental data for bubble growth rates and heat transfer coefficients.

  6. Mixing of high density solution in vertical upward flow

    International Nuclear Information System (INIS)

    Kumamaru, Hiroshige; Hosogi, Nobuyoshi; Komada, Toshiaki; Fujiwara, Yoshiki

    1999-01-01

    Experimental and analytical studies have been performed in order to provide fundamental data and a numerical calculation model on the mixing of boric acid solution, injected from the standby liquid control system (SLCS), under a low natural circulation flow during an ATWS in a BWR. First, fundamental experiments on the mixing of high-density solution in vertically-upward water flow have been performed by using a small apparatus. Mixing patterns observed in the experiments have been classified to two groups, i.e. complete mixing (entrainment) and incomplete mixing (entrainment). In the complete mixing, the injected high-density solution is mixed (entrained) completely into the vertically-upward water flow. From the experiments, the minimum water flow rates in which the complete mixing (entrainment) is achieved have been obtained for various solution densities and solution injection rates. Secondly, two-dimensional numerical calculations have been performed. A continuity equation for total fluid, momentum equations in two directions and a continuity equation for solute are solved by using the finite difference method for discretization method and by following the MAC method for solution procedure. The calculations have predicted nearly the minimum water flow rate in which the complete mixing is achieved, while the calculations have been performed only for one combination of the solution density and solution injection rate until now. (author)

  7. New biodegradable air-entraining admixture based on LAS for cement-based composites

    International Nuclear Information System (INIS)

    Mendes, J.C.; Moro, T.K.; Dias, L.S.; Campos, P.A.M.; Silva, G.J.B.; Peixoto, R.A.F.; Cury, A.A.

    2016-01-01

    The active principle of Air Entraining Admixtures (AEA) are surfactants, analogously to washing up liquids. Washing up (or dishwashing) liquids are widely available products, relatively inexpensive, non-toxic and biodegradable, thus presenting smaller environmental impact. Therefore, the present work proposes the use of a biodegradable surfactant comprised in washing up liquids, Linear Alkylbenzene Sulfonate (LAS), as sustainable air entraining agent for cement-based composites. In this sense, a performance evaluation of the proposed AEA is carried out, by comparing the properties of mortars with proposed AEA, commercial AEA and ones without any admixture. Through the physical, mechanical and microstructural analysis, it was possible to determine the efficiency of the proposed AEA, as well as its optimum range of dosage. As a result, we seek to contribute to the technical development of cement-based composites in Brazil and in the world. (author)

  8. Simultaneous design of ionic liquid entrainers and energy efficient azeotropic separation processes

    DEFF Research Database (Denmark)

    Roughton, Brock C.; Christian, Brianna; White, John

    2012-01-01

    A methodology and tool set for the simultaneous design of ionic liquid entrainers and azeotropic separation processes is presented. By adjusting the cation, anion, and alkyl chain length on the cation, the properties of the ionic liquid can be adjusted to design an entrainer for a given azeotropic...... mixture. Several group contribution property models available in literature have been used along with a newly developed group contribution solubility parameter model and UNIFAC model for ionic liquids (UNIFAC-IL). For a given azeotropic mixture, an ionic liquid is designed using a computer-aided molecular...... design (CAMD) method and the UNIFAC-IL model is used to screen design candidates based on minimum ionic liquid concentration needed to break the azeotrope. Once the ionic liquid has been designed, the extractive distillation column for the azeotropic mixture is designed using the driving force method...

  9. Dilution of aircraft exhaust and entrainment rates for trajectory box models

    Energy Technology Data Exchange (ETDEWEB)

    Gerz, T [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Kaercher, B [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung

    1998-12-31

    In order to match in-situ measured concentrations of NO and NO{sub 2} in the wake, dilution factors or entrainment rates have to be used which take into account that the largest fraction of the exhaust is captured by the wing tip vortices. This fraction defines the primary wake. Baroclinicity and turbulence detrains parts of it later into the secondary wake. Both wake regimes undergo different chemical and microphysical histories. The rates {omega} are determined at which ambient air becomes entrained into the primary and the secondary portion of the exhaust plume. Numerical simulations of the highly resolved wake is used of cruising aircraft under typical atmosphere conditions with and without ambient turbulence. The simulations are oriented on a case where exhaust and dynamical data behind an eastbound travelling B-747 aircraft have been collected in-situ over the North-Atlantic east of Ireland. (author) 7 refs.

  10. Experimental study on occurrence-time ratio measurements of air entrainment in a suction sump

    International Nuclear Information System (INIS)

    Inagaki, K; Funaki, J; Hirata, K

    2009-01-01

    In order to get accurate measurements of air entrainment in a suction sump, we design some new simple bubble sensors, which can detect the existence of air bubbles inside a suction pipe with no disturbances by the sensors and with a fine spatial resolution. We force on an intermittency factor γ, that is, an occurrence-time ratio of the air entrainment, and compare the result by the present sensor with those by conventional two methods; namely, visual and auditory ones. As a result, we show the criteria which specify lower-accuracy conditions in the conventional methods. By the visual method, the accuracy of the γ becomes low, when γ is less than 0.05. By the auditory method, the accuracy of γ becomes low, when the submergence depth S of the suction pipe is close to the critical one S c .

  11. The mammalian circadian clock and its entrainment by stress and exercise.

    Science.gov (United States)

    Tahara, Yu; Aoyama, Shinya; Shibata, Shigenobu

    2017-01-01

    The mammalian circadian clock regulates day-night fluctuations in various physiological processes. The circadian clock consists of the central clock in the suprachiasmatic nucleus of the hypothalamus and peripheral clocks in peripheral tissues. External environmental cues, including light/dark cycles, food intake, stress, and exercise, provide important information for adjusting clock phases. This review focuses on stress and exercise as potent entrainment signals for both central and peripheral clocks, especially in regard to the timing of stimuli, types of stressors/exercises, and differences in the responses of rodents and humans. We suggest that the common signaling pathways of clock entrainment by stress and exercise involve sympathetic nervous activation and glucocorticoid release. Furthermore, we demonstrate that physiological responses to stress and exercise depend on time of day. Therefore, using exercise to maintain the circadian clock at an appropriate phase and amplitude might be effective for preventing obesity, diabetes, and cardiovascular disease.

  12. Dilution of aircraft exhaust and entrainment rates for trajectory box models

    Energy Technology Data Exchange (ETDEWEB)

    Gerz, T. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Kaercher, B. [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung

    1997-12-31

    In order to match in-situ measured concentrations of NO and NO{sub 2} in the wake, dilution factors or entrainment rates have to be used which take into account that the largest fraction of the exhaust is captured by the wing tip vortices. This fraction defines the primary wake. Baroclinicity and turbulence detrains parts of it later into the secondary wake. Both wake regimes undergo different chemical and microphysical histories. The rates {omega} are determined at which ambient air becomes entrained into the primary and the secondary portion of the exhaust plume. Numerical simulations of the highly resolved wake is used of cruising aircraft under typical atmosphere conditions with and without ambient turbulence. The simulations are oriented on a case where exhaust and dynamical data behind an eastbound travelling B-747 aircraft have been collected in-situ over the North-Atlantic east of Ireland. (author) 7 refs.

  13. Effect of wall impingement on ambient gas entrainment, fuel evaporation and mixture formation of diesel spray

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, Keiya [Department of Mechanical Physics Engineering, University of Hiroshima (Japan); Matsumoto, Yuhei; Zhang, Wu [Mazda Motor Corp. (Japan); Gao, Jian [University of Wisconsin (United States); Moon, Seoksu [Argonne National Laboratory (United States)

    2010-07-01

    In the energy sector, with the implementation of stringent regulations on combustion emissions and the depletion of conventional fuels, there is a pressing need to improve the performance of engines. The purpose of this paper is to determine the impact of wall impingement on several characteristics of diesel spray. Experiments were carried out with both a small and a large amount of diesel spray injected and ambient gas entrainment, fuel evaporation and mixture formation were evaluated using an LAS optical system. Results showed that wall impingement has the same effects for small or large amounts of diesel spray injected; these are: a larger volume spray after the impingement and a smaller volume after it, the suppression of ambient gas entrainment and fuel evaporation, and the shift of the PDF peak of the vapor equivalent ratio. This study provided useful information but further work is needed to address the remaining issues.

  14. Entraining IDyOT: timing in the information dynamics of thinking

    Directory of Open Access Journals (Sweden)

    Jamie Forth

    2016-10-01

    Full Text Available We present a novel hypothetical account of entrainment in music and language, in context of the Information Dynamics of Thinking model, IDyOT. The extended model affords an alternative view of entrainment, and its companion term, pulse, from earlier accounts. The model is based on hiearchical, statistical prediction, modeling expectations of both what an event will be and when it will happen. As such,it constitutes a kind of predictive coding, with a particular novel hypothetical implementation. Here, we focus on the model’s mechanism for predicting when a perceptual event will happen, given an existing sequence of past events, which maybe musical or linguistic. We propose a range of tests to validate or falsify the model, at various different levels of abstraction, and argue that computational modelling in particular, and this model in particular, can offer a means of providing limited but useful evidence for evolutionary hypotheses.

  15. Rhythmic entrainment source separation: Optimizing analyses of neural responses to rhythmic sensory stimulation

    OpenAIRE

    Cohen, M.S.; Gulbinaite, R.

    2017-01-01

    Steady-state evoked potentials (SSEPs) are rhythmic brain responses to rhythmic sensory stimulation, and are often used to study perceptual and attentional processes. We present a data analysis method for maximizing the signal-to-noise ratio of the narrow-band steady-state response in the frequency and time-frequency domains. The method, termed rhythmic entrainment source separation (RESS), is based on denoising source separation approaches that take advantage of the simultaneous but differen...

  16. A Large Eddy Simulation Study of Heat Entrainment under Sea Ice in the Canadian Arctic Basin

    Science.gov (United States)

    Ramudu, E.; Yang, D.; Gelderloos, R.; Meneveau, C. V.; Gnanadesikan, A.

    2016-12-01

    Sea ice cover in the Arctic has declined rapidly in recent decades. The much faster than projected retreat suggests that climate models may be missing some key processes, or that these processes are not accurately represented. The entrainment of heat from the mixed layer by small-scale turbulence is one such process. In the Canadian Basin of the Arctic Ocean, relatively warm Pacific Summer Water (PSW) resides at the base of the mixed layer. With an increasing influx of PSW, the upper ocean in the Canadian Basin has been getting warmer and fresher since the early 2000s. While studies show a correlation between sea ice reduction and an increase in PSW temperature, others argue that PSW intrusions in the Canadian Basin cannot affect sea ice thickness because the strongly-stratified halocline prevents heat from the PSW layer from being entrained into the mixed layer and up to the basal ice surface. In this study, we try to resolve this conundrum by simulating the turbulent entrainment of heat from the PSW layer to a moving basal ice surface using large eddy simulation (LES). The LES model is based on a high-fidelity spectral approach on horizontal planes, and includes a Lagrangian dynamic subgrid model that reduces the need for empirical inputs for subgrid-scale viscosities and diffusivities. This LES tool allows us to investigate physical processes in the mixed layer at a very fine scale. We focus our study on summer conditions, when ice is melting, and show for a range of ice-drift velocities, halocline temperatures, and halocline salinity gradients characteristic of the Canadian Basin how much heat can be entrained from the PSW layer to the sea ice. Our results can be used to improve parameterizations of vertical heat flux under sea ice in coarse-grid ocean and climate models.

  17. Activating and relaxing music entrains the speed of beat synchronized walking.

    Science.gov (United States)

    Leman, Marc; Moelants, Dirk; Varewyck, Matthias; Styns, Frederik; van Noorden, Leon; Martens, Jean-Pierre

    2013-01-01

    Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is 'activating' in the sense that it increases the speed, and some music is 'relaxing' in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.

  18. Pulse and entrainment to non-isochronous auditory stimuli: the case of north Indian alap.

    Directory of Open Access Journals (Sweden)

    Udo Will

    Full Text Available Pulse is often understood as a feature of a (quasi- isochronous event sequence that is picked up by an entrained subject. However, entrainment does not only occur between quasi-periodic rhythms. This paper demonstrates the expression of pulse by subjects listening to non-periodic musical stimuli and investigates the processes behind this behaviour. The stimuli are extracts from the introductory sections of North Indian (Hindustani classical music performances (alap, jor and jhala. The first of three experiments demonstrates regular motor responses to both irregular alap and more regular jor sections: responses to alap appear related to individual spontaneous tempi, while for jor they relate to the stimulus event rate. A second experiment investigated whether subjects respond to average periodicities of the alap section, and whether their responses show phase alignment to the musical events. In the third experiment we investigated responses to a broader sample of performances, testing their relationship to spontaneous tempo, and the effect of prior experience with this music. Our results suggest an entrainment model in which pulse is understood as the experience of one's internal periodicity: it is not necessarily linked to temporally regular, structured sensory input streams; it can arise spontaneously through the performance of repetitive motor actions, or on exposure to event sequences with rather irregular temporal structures. Greater regularity in the external event sequence leads to entrainment between motor responses and stimulus sequence, modifying subjects' internal periodicities in such a way that they are either identical or harmonically related to each other. This can be considered as the basis for shared (rhythmic experience and may be an important process supporting 'social' effects of temporally regular music.

  19. Pulse and entrainment to non-isochronous auditory stimuli: the case of north Indian alap.

    Science.gov (United States)

    Will, Udo; Clayton, Martin; Wertheim, Ira; Leante, Laura; Berg, Eric

    2015-01-01

    Pulse is often understood as a feature of a (quasi-) isochronous event sequence that is picked up by an entrained subject. However, entrainment does not only occur between quasi-periodic rhythms. This paper demonstrates the expression of pulse by subjects listening to non-periodic musical stimuli and investigates the processes behind this behaviour. The stimuli are extracts from the introductory sections of North Indian (Hindustani) classical music performances (alap, jor and jhala). The first of three experiments demonstrates regular motor responses to both irregular alap and more regular jor sections: responses to alap appear related to individual spontaneous tempi, while for jor they relate to the stimulus event rate. A second experiment investigated whether subjects respond to average periodicities of the alap section, and whether their responses show phase alignment to the musical events. In the third experiment we investigated responses to a broader sample of performances, testing their relationship to spontaneous tempo, and the effect of prior experience with this music. Our results suggest an entrainment model in which pulse is understood as the experience of one's internal periodicity: it is not necessarily linked to temporally regular, structured sensory input streams; it can arise spontaneously through the performance of repetitive motor actions, or on exposure to event sequences with rather irregular temporal structures. Greater regularity in the external event sequence leads to entrainment between motor responses and stimulus sequence, modifying subjects' internal periodicities in such a way that they are either identical or harmonically related to each other. This can be considered as the basis for shared (rhythmic) experience and may be an important process supporting 'social' effects of temporally regular music.

  20. ETHANOL DEHYDRATION IN PACKED DISTILLATION COLUMN USING GLYCEROL AS ENTRAINER: EXPERIMENTS AND HETP EVALUATION

    OpenAIRE

    Souza,W. L. R.; Silva,C. S.; Meleiro,L. A. C.; Mendes,M. F.

    2016-01-01

    Abstract The ethanol-water separation is very important because ethanol is widely applied in the chemical industry and its use as a fuel can reduce the pollution emitted to the air. However, anhydrous ethanol production using conventional distillation is impossible, at atmospheric pressure, due to the presence of an azeotrope. In the present work, experimental tests were carried out in order to evaluate the use of glycerol as an entrainer, in substitution of ethylene glycol in an extractive d...

  1. Separation of ethanol and water by extractive distillation with salt and solvent as entrainer: process simulation

    OpenAIRE

    Gil, I. D.; Uyazán, A. M.; Aguilar, J. L.; Rodríguez, G.; Caicedo, L. A.

    2008-01-01

    The aim of this work is to simulate and analyze an extractive distillation process for azeotropic ethanol dehydration with ethylene glycol and calcium chloride mixture as entrainer. The work was developed with Aspen Plus® simulator version 11.1. Calculation of the activity coefficients employed to describe vapor liquid equilibrium of ethanol - water - ethylene glycol - calcium chloride system was done with the NRTL-E equation and they were validated with experimental data. The dehydration pro...

  2. Activating and relaxing music entrains the speed of beat synchronized walking.

    Directory of Open Access Journals (Sweden)

    Marc Leman

    Full Text Available Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is 'activating' in the sense that it increases the speed, and some music is 'relaxing' in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.

  3. Activating and Relaxing Music Entrains the Speed of Beat Synchronized Walking

    Science.gov (United States)

    Leman, Marc; Moelants, Dirk; Varewyck, Matthias; Styns, Frederik; van Noorden, Leon; Martens, Jean-Pierre

    2013-01-01

    Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is ‘activating’ in the sense that it increases the speed, and some music is ‘relaxing’ in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation. PMID:23874469

  4. Ichthyoplankton entrainment at Wylfa power station, Anglesey and implications for a further siting proposal

    International Nuclear Information System (INIS)

    Dempsey, C.H.; Rogers, S.I.

    1989-07-01

    A 12 month survey of ichthyoplankton in the cooling water system of Wylfa Power Station and the surrounding 40 km 2 of sea, was carried out between October 1986 and September 1987. The larvae of 31 species and the eggs of 8 species were identified in the survey. Samples taken from the cooling water system and by boat from offshore were largely similar in respect of species diversity and density. Estimates of annual losses due to entrainment are given both in terms of immediate losses and consequential losses of adults to the population. Estimates of losses of six commercially exploited species are considered in terms of loss to the commercial fishery. Assuming the 'worst case' of a 100% mortality of eggs and larvae passing through the cooling system, losses of ichthyoplankton due to entrainment at the existing 'magnox' nuclear power station at Wylfa Point are small and could have no significant adverse effect on fish populations of those species entrained. The operation of the proposed 'pressurised water reactor' nuclear power station on the same site would increase losses by up to 100%. Such an increase would still not alter the existing situation. No significant adverse effect is likely. (author)

  5. Mechanisms of basal ice formation in polar glaciers: An evaluation of the apron entrainment model

    Science.gov (United States)

    Fitzsimons, Sean; Webb, Nicola; Mager, Sarah; MacDonell, Shelley; Lorrain, Regi; Samyn, Denis

    2008-06-01

    Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up-glacier dip, and an outer element that lacks a consistent foliation and has a down-glacier, slope-parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co-isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.

  6. Investigations of entrainment mortality among larval and juvenile fishes using a Power Plant Simulator

    International Nuclear Information System (INIS)

    Cada, G.F.; Suffern, J.S.; Kumar, K.D.; Solomon, J.A.

    1980-01-01

    A Power Plant Simulator (PPS) was constructed at the Oak Ridge National Laboratory to examine the component sources of entrainment mortality. This experimental apparatus circulates temperature-controlled water through a closed loop consisting of a pump, a condenser bundle, and vertically adjustable piping. Larval bluegill, channel catfish, carp, largemouth bass, and smallmouth bass and juvenile bluegill and mosquitofish were exposed to different combinations of pump speed and water temperatures in the PPS. Wide differences among species in their sensitivity to pipe and condenser passage were observed. For most of the species tested, short-term conditional mortalities resulting from the physical stresses of pipe and condenser passage increased with ΔT and/or pumping rate. Pump passage was not a major source of physical damage, and no clear relationship was found between pump efficiency and mortality. Susceptibility to physical stresses associated with entrainment was inversely related to the size of the entrained organisms. Delayed mortality frequently occurred among fishes exposed to stresses in the PPS. However, delayed mortality estimates in these experimental groups were significantly greater than corresponding values in handling control groups in only 15 of 64 comparisons. Like short-term mortalities, relatively higher delayed mortalities were often observed for the smaller species tested

  7. Role of tempo entrainment in psychophysiological differentiation of happy and sad music?

    Science.gov (United States)

    Khalfa, Stéphanie; Roy, Mathieu; Rainville, Pierre; Dalla Bella, Simone; Peretz, Isabelle

    2008-04-01

    Respiration rate allows to differentiate between happy and sad excerpts which may be attributable to entrainment of respiration to the rhythm or the tempo rather than to emotions [Etzel, J.A., Johnsen, E.L., Dickerson, J., Tranel, D., Adolphs, R., 2006. Cardiovascular and respiratory responses during musical mood induction. Int. J. Psychophysiol. 61(1), 57-69]. In order to test for this hypothesis, this study intended to verify whether fast and slow rhythm, and/or tempo alone are sufficient to induce differential physiological effects. Psychophysiological responses (electrodermal responses, facial muscles activity, blood pressure, heart and respiration rate) were then measured in fifty young adults listening to fast/happy and slow/sad music, and to two control versions of these excerpts created by removing pitch variations (rhythmic version) and both pitch and temporal variations (beat-alone). The results indicate that happy and sad music are significantly differentiated (happy>sad) by diastolic blood pressure, electrodermal activity, and zygomatic activity, while the fast and slow rhythmic and tempo control versions did not elicit such differentiations. In contrast, respiration rate was faster with stimuli presented at fast tempi relative to slow stimuli in the beat-alone condition. It was thus demonstrated that the psychophysiological happy/sad distinction requires the tonal variations and cannot be explained solely by entrainment to tempo and rhythm. The tempo entrainment exists in the tempo alone condition but our results suggest this effect may disappear when embedded in music or with rhythm.

  8. Ichthyoplankton entrainment study at the SRS Savannah River water intakes for Westinghouse Savannah River Company

    International Nuclear Information System (INIS)

    Paller, M.

    1992-01-01

    Cooling water for L and K Reactors and makeup water for Par Pond is pumped from the Savannah River at the 1G, 3G, and 5G pump houses. Ichthyoplankton (drifting fish larvae and eggs) from the river are entrained into the reactor cooling systems with the river water and passed through the reactor's heat exchangers where temperatures may reach 70 degrees C during full power operation. Ichthyoplankton mortality under such conditions is assumed to be 100 percent. The number of ichthyoplankton entrained into the cooling system depends on a variety of variables, including time of year, density and distribution of ichthyoplankton in the river, discharge levels in the river, and the volume of water withdrawn by the pumps. Entrainment at the 1 G pump house, which is immediately downstream from the confluence of Upper Three Runs Creek and the Savannah River, is also influenced by discharge rates and ichthyoplankton densities in Upper Three Runs Creek. Because of the anticipated restart of several SRS reactors and the growing concern surrounding striped bass and American shad stocks in the Savannah River, the Department of Energy requested that the Environmental Sciences Section (ESS) of the Savannah River Laboratory sample ichthyoplankton at the SRS Savannah River intakes. Dams ampersand Moore, Inc., under a contract with Westinghouse Savannah River Company performed the sampling and data analysis for the ESS

  9. Literature search on slip and entrainment in a reactor cooling channel

    International Nuclear Information System (INIS)

    Beck, W.; Schuetzle, R.

    1976-11-01

    Models and correlations are presented describing slip and entrainment during the refilling phase after a LOCA in a PWR. Their applicability is investigated for a computer program to comprehend the processes in a reactor cooling channel during the refilling phase of the core. The models of Levy provide no realistic data for the problem discussed. Bankoff and Jones seem to predict reasonable results. Their half empirical relation is valid for void fractions α up to α approximately 0.75. Empirical correlations are applicable in smaller α-regions. Some relations cannot be evaluated on account of unknown quantities. When entrainment is concerned, often only the critical gas velocity at the onset is stated. It varies strongly. The correlations, describing the entrainment E, defined by the gas-stream, along the vertical axis z, provide values for E between 0.6 and 0.7 after a characteristic ascent at z = 0.5 - 0.6. Restrictions are frequently unknown. (orig./HP) [de

  10. Conceptual design of heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer

    Directory of Open Access Journals (Sweden)

    Paritta Prayoonyong

    2014-12-01

    Full Text Available The synthesis of a heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer is presented. The residue curve map of the ethanol/water/1-butanol mixture is computationally generated using non-random twoliquid thermodynamic model. It is found that 1-butanol leads to a residue curve map topological structure different from that generated by typical entrainers used in ethanol dehydration. Synthesised by residue curve map analysis, the distillation flowsheet for ethanol dehydration by 1-butanol comprises a double-feed column integrated with an overhead decanter and a simple column. The double-feed column is used to recover water as the top product, whereas the simple column is used for recovering ethanol and 1-butanol. The separation feasibility and the economically near-optimal designs of distillation columns in the flowsheet are evaluated and identified by using the boundary value design method. The distillation flowsheet using 1-butanol is compared with the conventional process using benzene as entrainer. Based on their total annualised costs, the ethanol dehydration process using 1-butanol is less economically attractive than the process using benzene. However, 1-butanol is less toxic than benzene.

  11. Biological effects of simulated discharge plume entrainment at Indian Point Nuclear Power Station, Hudson River estuary, USA

    International Nuclear Information System (INIS)

    Lanza, G.R.; Lauer, G.J.; Ginn, T.C.; Storm, P.C.; Zubarik, L.; New York Univ., N.Y.

    1975-01-01

    Laboratory and field simulations of the discharge plume entrainment of phytoplankton, zooplankton and fish were carried out at the Indian Point Nuclear Station, Hudson River estuary, USA. Phytoplankton assemblages studied on two dates produced different response patterns measured as photosynthetic activity. Chlorophyll-a levels did not change following simulated entrainment. Possible explanations for the differences are discussed. The two abundant copepods Acartia tonsa and Eurytemorta affinis appear to tolerate exposure to discharge plume ΔT without adverse effects. Copepods subjected to plume entrainment may suffer considerable mortality during periods of condenser chlorination. In general, the amphipod Gammarus spp. did not appear to suffer significant mortality during simulated entrainment. Juvenile striped bass, Morone saxatilis, were not affected by simulated plume transit before and during plant condenser chlorination; however, a simulated ''worst possible case'' plume ΔT produced statistically significant moralities. (author)

  12. Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

    Science.gov (United States)

    Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

    Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

  13. Experimental analysis of the thermal entrainment factor of air curtains in vertical open display cabinets for different ambient air conditions

    International Nuclear Information System (INIS)

    Gaspar, Pedro Dinis; Carrilho Goncalves, L.C.; Pitarma, R.A.

    2011-01-01

    The vertical open refrigerated display cabinets suffer alterations of their thermal performance and energy efficiency due to variations of ambient air conditions. The air curtain provides an aerothermodynamics insulation effect that can be evaluated by the thermal entrainment factor calculation as an engineering approximation or by the calculus of all sensible and latent thermal loads. This study presents the variation of heat transfer rate and thermal entrainment factor obtained through experimental tests carried out for different ambient air conditions, varying air temperature, relative humidity, velocity and its direction relatively to the display cabinet frontal opening. The thermal entrainment factor are analysed and compared with the total sensible and latent heats results for the experimental tests. From an engineering point of view, it is concluded that thermal entrainment factor cannot be used indiscriminately, although its use is suitable to design better cabinet under the same climate class condition.

  14. Entrainment of the Circadian Rhythm in Egg Hatching of the Crab Dyspanopeus sayi by Chemical Cues from Ovigerous Females.

    Science.gov (United States)

    Forward, Richard B; Sanchez, Kevin G; Riley, Paul P

    2016-02-01

    The subtidal crab Dyspanopeus sayi has a circadian rhythm in larval release with a free-running period of 24.1 h. Under constant conditions, eggs hatch primarily in the 4-h interval after the time of sunset. The study tested the new model for entrainment in subtidal crabs, which proposes that the female perceives the environmental cycles and entrains the endogenous rhythm in the embryos. Results verified the model for D. sayi. Hatching by embryos collected from the field when they had not yet developed eye pigments, and were kept in constant conditions attached to their mother, exhibited the circadian hatching rhythm. Attached embryos could also be entrained to a new photoperiod in the laboratory before they developed eye pigments. Further, mature embryos removed from the female hatched rhythmically, indicating that a circadian rhythm resides in the embryos. However, if mature embryos with eye pigments were removed from the female and exposed to a new light-dark cycle, they could not be entrained to the new cycle; rather, they hatched according to the timing of the original light-dark cycle. Nevertheless, detached, mature embryos would entrain to a new light-dark cycle if they were in chemical, but not physical, contact with the female. Thus, the female perceives the light-dark cycle, and uses chemical cues to entrain the circadian rhythm of hatching by the embryos. © 2016 Marine Biological Laboratory.

  15. Time-dependent effects of dim light at night on re-entrainment and masking of hamster activity rhythms.

    Science.gov (United States)

    Frank, David W; Evans, Jennifer A; Gorman, Michael R

    2010-04-01

    Bright light has been established as the most ubiquitous environmental cue that entrains circadian timing systems under natural conditions. Light equivalent in intensity to moonlight (dim nighttime illumination accelerated re-entrainment of hamster activity rhythms to 4-hour phase advances and delays of an otherwise standard laboratory photocycle. The purpose of this study was to determine if a sensitive period existed in the night during which dim illumination had a robust influence on speed of re-entrainment. Male Siberian hamsters were either exposed to dim light throughout the night, for half of the night, or not at all. Compared to dark nights, dim illumination throughout the entire night decreased by 29% the time for the midpoint of the active phase to re-entrain to a 4-hour phase advance and by 26% for a 4-hour delay. Acceleration of advances and delays were also achieved with 5 hours of dim light per night, but effects depended on whether dim light was present in the first half, second half, or first and last quarters of the night. Both during phase shifting and steady-state entrainment, partially lit nights also produced strong positive and negative masking effects, as well as entrainment aftereffects in constant darkness. Thus, even in the presence of a strong zeitgeber, light that might be encountered under a natural nighttime sky potently modulates the circadian timing system of hamsters.

  16. Mechanical effects of water flow on fish eggs and larvae

    International Nuclear Information System (INIS)

    Ulanowicz, R.E.

    1975-01-01

    The impact of mechanical stresses on ichthyoplankton entrained in power plant cooling systems has long been considered negligible. Arguments and evidence exist, however, to show that such a supposition is not universally true, especially in nuclear power plants. The mechanisms of mechanical damage can be detailed in terms of pressure change, acceleration, and shear stress within the fluid flow field. (U.S.)

  17. Determination of dryout localization using a five-equation model of annular flow for boiling in minichannels

    OpenAIRE

    Wajs Jan; Mikielewicz Dariusz

    2017-01-01

    Detailed studies have suggested that the critical heat flux in the form of dryout in minichannels occurs when the combined effects of entrainment, deposition, and evaporation of the film make the film flow rate go gradually and smoothly to zero. Most approaches so far used the mass balance equation for the liquid film with appropriate formulations for the rate of deposition and entrainment respectively. It must be acknowledged that any discrepancy in determination of deposition and entrainmen...

  18. Measurement of two-phase flow momentum with force transducers

    International Nuclear Information System (INIS)

    Hardy, J.E.; Smith, J.E.

    1990-01-01

    Two strain-gage-based drag transducers were developed to measure two-phase flow in simulated pressurized water reactor (PWR) test facilities. One transducer, a drag body (DB), was designed to measure the bidirectional average momentum flux passing through an end box. The second drag sensor, a break through detector (BTD), was designed to sense liquid downflow from the upper plenum to the core region. After prototype sensors passed numerous acceptance tests, transducers were fabricated and installed in two experimental test facilities, one in Japan and one in West Germany. High-quality data were extracted from both the DBs and BTDs for a variety of loss-of-coolant accident (LOCA) scenarios. The information collected from these sensors has added to the understanding of the thermohydraulic phenomena that occur during the refill/reflood stage of a LOCA in a PWR. 9 refs., 15 figs

  19. The effects of a flow obstacle on liquid film flowing concurrently with air in a horizontal rectangular duct

    International Nuclear Information System (INIS)

    Fukano, Tohru; Tominaga, Akira; Morikawa, Kengo.

    1986-01-01

    The aspect of a liquid film flowing near a flat plate type obstacle was observed, and the liquid film thickness and the entrainment were measured under a wide range of gas and liquid flow rates. The results are summarized as follows: (1) The configurations of film flows near the obstacle are classified according to whether (a) the liquid film climbs over the obstacle or not, (b) the air flows under the obstacle or not, or (c) the liquid film swells or sinks just upstream or downstream of the obstacle. (2) The lower the liquid flow rate, the larger the effect of the obstacle on the film thickness. (3) The generation of entrainment is regulated by the obstacle when the air volumetric flux is high and by the disturbance wave when it is low. (author)

  20. Observations of debris flows at Chalk Cliffs, Colorado, USA: Part 1, in-situ measurements of flow dynamics, tracer particle movement and video imagery from the summer of 2009

    Science.gov (United States)

    McCoy, Scott W.; Coe, Jeffrey A.; Kean, Jason W.; Tucker, Greg E.; Staley, Dennis M.; Wasklewicz, Thad A.

    2011-01-01

    Debris flows initiated by surface-water runoff during short duration, moderate- to high-intensity rainfall are common in steep, rocky, and sparsely vegetated terrain. Yet large uncertainties remain about the potential for a flow to grow through entrainment of loose debris, which make formulation of accurate mechanical models of debris-flow routing difficult. Using a combination of in situ measurements of debris flow dynamics, video imagery, tracer rocks implanted with passive integrated transponders (PIT) and pre- and post-flow 2-cm resolution digital terrain models (terrain data presented in a companion paper by STALEY et alii, 2011), we investigated the entrainment and transport response of debris flows at Chalk Cliffs, CO, USA. Four monitored events during the summer of 2009 all initiated from surface-water runoff, generally less than an hour after the first measurable rain. Despite reach-scale morphology that remained relatively constant, the four flow events displayed a range of responses, from long-runout flows that entrained significant amounts of channel sediment and dammed the main-stem river, to smaller, short-runout flows that were primarily depositional in the upper basin. Tracer-rock travel-distance distributions for these events were bimodal; particles either remained immobile or they travelled the entire length of the catchment. The long-runout, large-entrainment flow differed from the other smaller flows by the following controlling factors: peak 10-minute rain intensity; duration of significant flow in the channel; and to a lesser extent, peak surge depth and velocity. Our growing database of natural debris-flow events can be used to develop linkages between observed debris-flow transport and entrainment responses and the controlling rainstorm characteristics and flow properties.

  1. The value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure

    Directory of Open Access Journals (Sweden)

    Hong-Zhuan Song

    Full Text Available OBJECTIVE: To investigate the value of high-flow nasal cannula oxygen therapy after extubation in patients with acute respiratory failure. METHODS: A single-center, prospective, randomized, controlled pilot trial was conducted between January 2013 and December 2014. Sixty enrolled patients were randomized immediately after extubation into either a high-flow nasal cannula group (n=30 or an air entrainment mask group (n=30 at a fixed inspired oxygen fraction (40%. The success rate of oxygen therapy, respiratory and hemodynamic parameters and subjective discomfort (using a visual analogue scale were assessed at 24h after extubation. RESULTS: The two groups were comparable at extubation. A total of 46 patients were successfully treated including 27 patients in the high-flow nasal cannula group and 19 patients in the air entrainment mask group. Compared to the air entrainment mask group, the success rate of oxygen therapy and the partial pressure of arterial oxygen were significantly higher and the respiratory rate was lower in the high-flow nasal cannula group. In addition, less discomfort related to interface displacement and airway dryness was observed in the high-flow nasal cannula group than in the air entrainment mask group. CONCLUSIONS: At a fixed inspired oxygen fraction, the application of a high-flow nasal cannula after extubation achieves a higher success rate of oxygen therapy and less discomfort at 24h than an air entrainment mask in patients with acute respiratory failure.

  2. Gasification of peat and biomass in suspension flow 2; Turpeen ja biomassan suspensiokaasutus 2

    Energy Technology Data Exchange (ETDEWEB)

    Kurkela, E.; Hepola, J. [VTT Energy, Espoo (Finland); Haukka, P.; Raiko, R. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Thermal Engineering

    1995-11-01

    This project is an extension of the earlier Liekki-project 402, which was carried out in 1993-1994 in the Department of Thermal Engineering of Tampere University of Technology (TUT). In the previous project the feasibility of a two-stage entrained-flow gasification was studied by the means of process modeling and pyrolysis experiments. The present project carried out in cooperation with the Gasification Research Group of VTT and TUT. The aims of the project are: (a) to study the formation of blematic tar/soot compounds and nitrogen compounds in the conditions entrained flow gasification of biomass and peat, (b) to study the product yields and kinetics of pyrolysis and (c) to develop simulation methods for entrained flow pyrolysis and gasification. (author)

  3. Entrainment of Breast Cell Lines Results in Rhythmic Fluctuations of MicroRNAs

    Directory of Open Access Journals (Sweden)

    Rafael Chacolla-Huaringa

    2017-07-01

    Full Text Available Circadian rhythms are essential for temporal (~24 h regulation of molecular processes in diverse species. Dysregulation of circadian gene expression has been implicated in the pathogenesis of various disorders, including hypertension, diabetes, depression, and cancer. Recently, microRNAs (miRNAs have been identified as critical modulators of gene expression post-transcriptionally, and perhaps involved in circadian clock architecture or their output functions. The aim of the present study is to explore the temporal expression of miRNAs among entrained breast cell lines. For this purpose, we evaluated the temporal (28 h expression of 2006 miRNAs in MCF-10A, MCF-7, and MDA-MB-231 cells using microarrays after serum shock entrainment. We noted hundreds of miRNAs that exhibit rhythmic fluctuations in each breast cell line, and some of them across two or three cell lines. Afterwards, we validated the rhythmic profiles exhibited by miR-141-5p, miR-1225-5p, miR-17-5p, miR-222-5p, miR-769-3p, and miR-548ay-3p in the above cell lines, as well as in ZR-7530 and HCC-1954 using RT-qPCR. Our results show that serum shock entrainment in breast cells lines induces rhythmic fluctuations of distinct sets of miRNAs, which have the potential to be related to endogenous circadian clock, but extensive investigation is required to elucidate that connection.

  4. Entrainment to feeding but not to light: circadian phenotype of VPAC2 receptor-null mice.

    Science.gov (United States)

    Sheward, W John; Maywood, Elizabeth S; French, Karen L; Horn, Jacqueline M; Hastings, Michael H; Seckl, Jonathan R; Holmes, Megan C; Harmar, Anthony J

    2007-04-18

    The master clock driving mammalian circadian rhythms is located in the suprachiasmatic nuclei (SCN) of the hypothalamus and entrained by daily light/dark cycles. SCN lesions abolish circadian rhythms of behavior and result in a loss of synchronized circadian rhythms of clock gene expression in peripheral organs (e.g., the liver) and of hormone secretion (e.g., corticosterone). We examined rhythms of behavior, hepatic clock gene expression, and corticosterone secretion in VPAC2 receptor-null (Vipr2-/-) mice, which lack a functional SCN clock. Unexpectedly, although Vipr2-/- mice lacked robust circadian rhythms of wheel-running activity and corticosterone secretion, hepatic clock gene expression was strongly rhythmic, but advanced in phase compared with that in wild-type mice. The timing of food availability is thought to be an important entrainment signal for circadian clocks outside the SCN. Vipr2-/- mice consumed food significantly earlier in the 24 h cycle than wild-type mice, consistent with the observed timing of peripheral rhythms of circadian gene expression. When restricted to feeding only during the daytime (RF), mice develop rhythms of activity and of corticosterone secretion in anticipation of feeding time, thought to be driven by a food-entrainable circadian oscillator, located outside the SCN. Under RF, mice of both genotypes developed food-anticipatory rhythms of activity and corticosterone secretion, and hepatic gene expression rhythms also became synchronized to the RF stimulus. Thus, food intake is an effective zeitgeber capable of coordinating circadian rhythms of behavior, peripheral clock gene expression, and hormone secretion, even in the absence of a functional SCN clock.

  5. Activating and relaxing music entrains the speed of beat synchronized walking

    OpenAIRE

    Leman, Marc; Moelants, Dirk; Varewyck, Matthias; Styns, Frederik; van Noorden, Leon; Martens, Jean-Pierre

    2013-01-01

    Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musi...

  6. An ongoing investigation on modeling the strength properties of water-entrained cement-based materials

    DEFF Research Database (Denmark)

    Esteves, L.P.

    2012-01-01

    Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent......-based materials. Beyond the discussion of whether or not the introduction of superabsorbent polymers leads to a strength reduction, this paper uses both experimental and theoretical background to separate the effect of SAP in both pore structure and internal relative humidity and the effect from the active...

  7. Foaming and Antifoaming and Gas Entrainment in Radioactive Waste Pretreatment and Immobilization Processes. Final Report

    International Nuclear Information System (INIS)

    Wasan, Darsh T.

    2007-01-01

    The Savannah River Site (SRS) and Hanford site are in the process of stabilizing millions of gallons of radioactive waste slurries remaining from production of nuclear materials for the Department of Energy (DOE). The Defense Waste Processing Facility (DWPF) at SRS is currently vitrifying the waste in borosilicate glass, while the facilities at the Hanford site are in the construction phase. Both processes utilize slurry-fed joule-heated melters to vitrify the waste slurries. The DWPF has experienced difficulty during operations. The cause of the operational problems has been attributed to foaming, gas entrainment and the rheological properties of the process slurries. The rheological properties of the waste slurries limit the total solids content that can be processed by the remote equipment during the pretreatment and meter feed processes. Highly viscous material can lead to air entrainment during agitation and difficulties with pump operations. Excessive foaming in waste evaporators can cause carryover of radionuclides and non-radioactive waste to the condensate system. Experimental and theoretical investigations of the surface phenomena, suspension rheology and bubble generation of interactions that lead to foaming and air entrainment problems in the DOE High Level and Low Activity Radioactive Waste separation and immobilization processes were pursued under this project. The first major task accomplished in the grant proposal involved development of a theoretical model of the phenomenon of foaming in a three-phase gas-liquid-solid slurry system. This work was presented in a recently completed Ph.D. thesis (9). The second major task involved the investigation of the inter-particle interaction and microstructure formation in a model slurry by the batch sedimentation method. Both experiments and modeling studies were carried out. The results were presented in a recently completed Ph.D. thesis. The third task involved the use of laser confocal microscopy to study

  8. Study of the Influence of an Air-Entraining Agent on the Rheology of Motars

    Directory of Open Access Journals (Sweden)

    Tebbal Nadia

    2018-01-01

    Experimental studies have been carried out to study the effect of air entrainment on compressive strength, density and ingredients of fresh concrete mix. During all the study, water cement ratio (w/c was maintained constant at 0.5. The results have shown substantial decreasing in water and mortar density followed with decreasing in compressive strength of mortar. The results of this study has given more promising to use it as a guide for mortar mix design to choose the most appropriate concrete mix design economically.

  9. Laboratory study of orographic cloud-like flow

    Science.gov (United States)

    Singh, Kanwar Nain; Sreenivas, K. R.

    2013-11-01

    Clouds are one of the major sources of uncertainty in climate prediction, listed in ``the most urgent scientific problems requiring attention'' IPCC. Also, convective clouds are of utmost importance to study the dynamics of tropical meteorology and therefore, play a key role in understanding monsoons. The present work is to study the dynamics of orographic clouds. Parameterization of these clouds will help in forecasting the precipitation accurately. Also, one could validate laboratory results from our study by actually measuring cloud development along a sloping terrain. In this context a planar buoyant turbulent wall jet is considered as an appropriate low order fluid-dynamical model for studying the turbulence and entrainment in orographic-clouds. Flow is volumetrically heated to mimic the latent heat release due to condensation in an actual cloud. This is the first step in studying the entrainment dynamics of the evolving orographic cloud. We are going to present some results on the cloud development using techniques that allows us to construct a 3-dimensional flow field at each instance and its development over the time. By combining velocity field from PIV and flow volume from PLIF at successive instances, we estimate the entrainment coefficient. Since the life-cycle of a cloud is determined by the entrainment of ambient air, these results could be extremely helpful in understanding the dynamics of the clouds. Detailed results will be presented at the conference.

  10. Program determines two-phase flow

    International Nuclear Information System (INIS)

    Yamashiro, C.E.; Espiell, L.G.S.; Farina, I.H.

    1986-01-01

    When a mixture of a gas and a liquid flows along a horizontal pipe, it is possible to have up to seven different flow patterns. These flow patterns are: 1. Dispersed. When nearly all the liquid is entrained as spray by the gas; 2. Annular. The liquid forms a film around the inside wall of the pipe, and the gas flows at a high velocity as a central core; 3. Bubble. Bubbles of gas move along at about the same velocity as the liquid; 4. Stratified. The liquid flows along the bottom of the pipe and the gas flows above over a smooth gas-liquid interface; 5. Wave. Is similar to stratified except the interface is disturbed by waves moving in the direction of flow; 6. Slug. Waves are picked up periodically in the form of frothy slugs that