WorldWideScience

Sample records for concentric annular flows

  1. Concentration Measurements in a Cold Flow Model Annular Combustor Using Laser Induced Fluorescence

    Science.gov (United States)

    Morgan, Douglas C.

    1996-01-01

    A nonintrusive concentration measurement method is developed for determining the concentration distribution in a complex flow field. The measurement method consists of marking a liquid flow with a water soluble fluorescent dye. The dye is excited by a two dimensional sheet of laser light. The fluorescent intensity is shown to be proportional to the relative concentration level. The fluorescent field is recorded on a video cassette recorder through a video camera. The recorded images are analyzed with image processing hardware and software to obtain intensity levels. Mean and root mean square (rms) values are calculated from these intensity levels. The method is tested on a single round turbulent jet because previous concentration measurements have been made on this configuration by other investigators. The previous results were used to comparison to qualify the current method. These comparisons showed that this method provides satisfactory results. 'Me concentration measurement system was used to measure the concentrations in the complex flow field of a model gas turbine annular combustor. The model annular combustor consists of opposing primary jets and an annular jet which discharges perpendicular to the primary jets. The mixing between the different jet flows can be visualized from the calculated mean and rms profiles. Concentration field visualization images obtained from the processing provide further qualitative information about the flow field.

  2. Investigation for Transient Phenomena in Concentric Annular Turbulent Flow with Sudden Outer-Wall-Rotation

    OpenAIRE

    岡本, 正芳; 永江, 聡美; Masayoshi, OKAMOTO; Satomi, NAGAE; 静岡大工; 東北大流体研; Dept. of Mech. Eng., Shizuoka Univ.; Institute of Fluid Science, Tohoku Univ.

    2007-01-01

    Transient phenomena in turbulent concentric annular pipe flow with sudden outer-wall rotation were investigated by means of the direct numerical simulation (DNS). Due to the sudden rotation, the wall friction becomes small and the flow is stabilized. In the transient state, the axial mean velocity profile changes drastically and the Reynolds stresses vanish near the outer wall. When the wall friction increases suddenly, the vortex structures are invigorated.

  3. PRESSURE AND VELOCITY AMPLITUDES OF THE INCOMPRESSIBLE FLUID IN CONCENTRIC ANNULAR PASSAGE WITH OSCILLATORY BOUNDARY: TURBULENT FLOW

    Directory of Open Access Journals (Sweden)

    ABOLGHASEM MEKANIK

    2014-04-01

    Full Text Available An unsteady program based on a turbulence model called Baseline (BSL komega model was conducted to simulate three turbulent flows with Re numbers of 4×103, 8×103 and 1×104, between two initially concentric cylinders. The effects of principal flow variables, i.e., mean axial velocity and fluid temperature, annular passage configurations, i.e., the gap width and radii of cylinders on the pressure and circumferential velocity of a three dimensional turbulent flow in the annular passage were investigated. The results were validated with the available solutions in the literature and fairly good agreements are seen. By increasing the gap of the annular passage and the axial flow velocity, smaller values for the unsteady pressure and the circumferential velocity amplitudes are produced. For each of the turbulent flows the unsteady pressure amplitude increases with the fluid temperature, as well as the circumferential velocity amplitude. The results of this investigation are favorably used for FIV and FSI calculations in such configurations.

  4. Benign concentric annular macular dystrophy

    Directory of Open Access Journals (Sweden)

    Luísa Salles de Moura Mendonça

    2015-06-01

    Full Text Available The purpose of the authors is to show clinical findings of a patient with benign concentric annular macular dystrophy, which is an unusual condition, and part of the "bull’s eye" maculopathy differential diagnosis. An ophthalmologic examination with color perception, fluorescein angiography, and ocular electrophysiology was performed.

  5. On the mixing enhancement in annular flows

    Science.gov (United States)

    Moradi, H. V.; Floryan, J. M.

    2017-02-01

    The potential for mixing enhancement associated with the use of axisymmetric ribs in annular flows has been analyzed. The enhancement relies on the use of streamwise vortices produced by the centrifugal instability. Conditions leading to the formation of such vortices have been established for a wide range of geometric parameters of interest using linear stability theory. It has been demonstrated that vortices can be formed only in the presence of ribs with O(1) wavelengths. Slopes of the bounding walls in the case of the long wavelength ribs are too small to create centrifugal forces sufficient for flow destabilization. In the case of short wavelength ribs, the slopes become excessively large, resulting in the stream moving away from the wall and becoming rectilinear and, thus, reducing the magnitude of the centrifugal force field. It has been shown that decreasing the annulus' radius reduces the critical Reynolds number when ribs are placed at the inner cylinder but increases when the ribs are placed at the outer cylinder. The onset of the shear-driven instability has been investigated as the resulting travelling waves may interfere with the formation of vortices. It has been shown that the axisymmetric waves play the critical role for annuli with large radii while the spiral waves play the critical role for annuli with small radii. The ribs always reduce the critical Reynolds number for the travelling waves when compared with the onset conditions for smooth annuli. The conduit geometries giving preference to the formation of vortices while avoiding creation of the travelling waves have been identified. It is demonstrated that predictions of flow characteristics determined through the analysis of sinusoidal ribs provide a good approximation of the flow response to ribs of arbitrary shape.

  6. Inverted annular flow heat transfer in a natural circulation loop

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, M.; Umekawa, H.; Shiba, Y.; Yano, T. [Kansai Univ., Osaka (Japan)

    1998-07-01

    Gravity-feed reflooding experiment was conducted in a natural circulation loop of liquid nitrogen. The cooling curve of high temperature tube wall had a characteristic feature, i.e. initial rapid cooling with steam binding, relatively long-time plateau, gradual decrease with or without flow oscillation, and final drastic decrease during quenching process. Such phenomena had close relationship to the heated wall dynamics and heating power transient. To provide fundamental understanding on the present phenomena, the heat transfer data in inverted annular and dispersed flows were obtained under steady or oscillatory flow condition. The experimental data suggested that the heat transfer coefficient in the inverted annular or dispersed flow regimes is a slightly increasing function of heat flux but significantly depended on the tube diameter. The flow oscillation deteriorated heat transfer slightly in the inverted annular and dispersed flow regimes but significantly in the quenching process.

  7. Hydraulic study of drilling fluid flow in circular and annular tubes

    Energy Technology Data Exchange (ETDEWEB)

    Scheid, C.M.; Calcada, L.A.; Braga, E.R.; Paraiso, E.C.H. [Universidade Federal Rural do Rio de Janeiro (PPGEQ/UFRRJ), Seropedica, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Quimica. Dept. de Engenharia Qumica], E-mail: calcada@ufrrj.br; Martins, A. L. [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2011-10-15

    This study investigates the drilling fluid flow behavior of two water-based drilling fluids in circular and annular tubes. The study has four main objectives: 1) to evaluate correlations between the Power Law and the Casson rheological models, 2) to characterize the flow behavior, 3) to evaluate five hydraulic-diameter equations, and 4) to evaluate the correlations of five turbulent flow-friction factors. The experimental fluid flow loop consisted of one positive displacement pump of 25 HP connected to a 500-liter tank agitated by a 3-HP mixer. The fluids passed through six meters long tubes, arranged in three horizontal rows with independent inlets and outlets. The circular tubes had a 1 inch diameter and were configured as two concentric annular tubes. Annular Tube I had an outer diameter of 1 1/4 inch and an inner diameter of 1/2 inch. Annular Tube II had an outer diameter of 2 inches and an inner diameter of 3/4 inch. The results show that, for the fluids in exam, correlations proposed in the literature were inaccurate as far as predicting hydraulic diameter, estimating pressure drop, and defining the flow regime. In general, the performance of those correlations depended on the fluid properties and on the system's geometry. Finally, literature parameters for some of the correlations were estimated for the two drilling fluids studied. These estimations improved the predictive capacity of calculating the friction factor for real drilling fluids applications for both circular and annular tubes. (author)

  8. Elastic instability in stratified core annular flow.

    Science.gov (United States)

    Bonhomme, Oriane; Morozov, Alexander; Leng, Jacques; Colin, Annie

    2011-06-01

    We study experimentally the interfacial instability between a layer of dilute polymer solution and water flowing in a thin capillary. The use of microfluidic devices allows us to observe and quantify in great detail the features of the flow. At low velocities, the flow takes the form of a straight jet, while at high velocities, steady or advected wavy jets are produced. We demonstrate that the transition between these flow regimes is purely elastic--it is caused by the viscoelasticity of the polymer solution only. The linear stability analysis of the flow in the short-wave approximation supplemented with a kinematic criterion captures quantitatively the flow diagram. Surprisingly, unstable flows are observed for strong velocities, whereas convected flows are observed for low velocities. We demonstrate that this instability can be used to measure the rheological properties of dilute polymer solutions that are difficult to assess otherwise.

  9. Elastic instability in stratified core annular flow

    CERN Document Server

    Bonhomme, Oriane; Leng, Jacques; Colin, Annie

    2010-01-01

    We study experimentally the interfacial instability between a layer of dilute polymer solution and water flowing in a thin capillary. The use of microfluidic devices allows us to observe and quantify in great detail the features of the flow. At low velocities, the flow takes the form of a straight jet, while at high velocities, steady or advected wavy jets are produced. We demonstrate that the transition between these flow regimes is purely elastic -- it is caused by viscoelasticity of the polymer solution only. The linear stability analysis of the flow in the short-wave approximation captures quantitatively the flow diagram. Surprisingly, unstable flows are observed for strong velocities, whereas convected flows are observed for low velocities. We demonstrate that this instability can be used to measure rheological properties of dilute polymer solutions that are difficult to assess otherwise.

  10. Droplet sizes, dynamics and deposition in vertical annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, J C.B.; Dukler, A E

    1985-10-01

    The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data.

  11. Flow of viscoplastic fluids in eccentric annular geometries

    DEFF Research Database (Denmark)

    Szabo, Peter; Hassager, Ole

    1992-01-01

    A classification of flowfields for the flow of a Bingham fluid in general eccentric annular geometries is presented. Simple arguments show that a singularity can exist in the stress gradient on boundaries between zones with yielded and un-yielded fluid respectively. A Finite Element code is used...... to verify this property of the Bingham fluid. An analytical solution for the flowfield in case of small eccentricities is derived....

  12. Two-phase flow instabilities in a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Babelli, I.; Nair, S.; Ishii, M. [Purdue Univ., West Lafayette, IN (United States)

    1995-09-01

    An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.

  13. Numerical simulation of a viscoelastic flow through a concentric annular with BSD scheme, influence of the Deborah number; Simulacao numerica do escoamento laminar de fluido viscoelastico PTT (Phan-Thien-Tanner) em tubo anular concentrico - influencia do numero de Deborah

    Energy Technology Data Exchange (ETDEWEB)

    D' Ambros, Alder C.; Vitorassi, Pedro H.; Franco, Admilson T.; Morales, Rigoberto E.M. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Matins, Andre Leibsohn [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Tecnologia de Engenharia de Perfuracao

    2008-07-01

    The success of oil well drilling process depends on the correct prediction of the velocities and stresses fields inside the gap between the drill string and the rock formation. Using CFD is possible to predict the behavior of the drilling fluid flow along the annular space, from the bottom to the top of the well. Commonly the drilling fluid is modeled as a Herschel-Bulkley fluid. An alternative is to employ a non-linear viscoelastic model, like the one developed by Phan-Thien-Tanner (PTT). In the present work the PTT constitutive equation is used to model the drilling fluid flow along the annular space. Thus, this work investigates the influence of the Deborah number on the laminar flow pattern through the numerical solution of the equations formed by the coupled velocity-pressure-stress fields. The results are analyzed and validated against the analytical solution for the fully developed annular pipe flow. The relation between the Deborah number (De) and the entry length is investigated, along with the influence of high values of Deborah number on the friction factor, stress and velocity fields. (author)

  14. Flow properties of particles in a model annular shear cell

    Science.gov (United States)

    Wang, X.; Zhu, H. P.; Yu, A. B.

    2012-05-01

    In order to quantitatively investigate the mechanical and rheological properties of solid flow in a shear cell under conditions relevant to those in an annular cell, we performed a series of discrete particle simulations of slightly polydispersed spheres from quasi-static to intermediate flow regimes. It is shown that the average values of stress tensor components are uniformly distributed in the cell space away from the stationary walls; however, some degree of inhomogeneity in their spatial distributions does exist. A linear relationship between the (internal/external) shear and normal stresses prevails in the shear cell and the internal and external friction coefficients can compare well with each other. It is confirmed that annular shear cells are reasonably effective as a method of measuring particle flow properties. The so-called I-rheology proposed by Jop et al. [Nature (London) 441, 727 (2006)] is rigorously tested in this cell system. The results unambiguously display that the I-rheology can effectively describe the intermediate flow regime with a high correlation coefficient. However, significant deviations take place when it is applied to the quasi-static regime, which corresponds to very small values of inertial number.

  15. Flow measurements in a curved-wall annular contraction

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, A.K.; Tinneti, A.; Gollahalli, S.R. [Univ. of Oklahoma, Norman, OK (United States). Gas Turbine Systems Lab.

    1999-07-01

    Flow development in an annular contraction is of fundamental and practical importance in various applications including the gas turbine systems. This paper describes an experimental study of flow characteristics in a curved wall annular contraction. The results are presented in terms of the velocity vectors, surface pressure coefficients, static and stagnation pressure distributions, and profiles of mean velocities, turbulence intensity, and Reynolds shear stress. The flow conditions at the entrance were varied to evaluate how they affected the flow development in the passage. Results show that the contraction produced uniform static pressure and axial velocity profiles at the exit plane. Higher inlet turbulence affected the Reynolds shear stress in the contraction although the change in the static and total pressure fields was insignificant. The overall stagnation pressure loss was only 2 to 3 percent of the dynamic head at the contraction exit plane. Results showing only typical data are included in this paper. More extensive data sets to validate computer codes are available from the authors.

  16. Characterization of interfacial waves in horizontal core-annular flow

    Science.gov (United States)

    Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

    2016-11-01

    In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

  17. Droplet entrainment rate in gas-liquid annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, P. [Energy Research Inc., Rockville, Maryland (United States); Liu, Y.; Ishii, M. [Purdue Univ., West Lafayette, Indiana (United States); Mori, M. [Tokyo Electric Power Co., Inc., Yokohama (Japan); Chen, S. [Purdue Univ., West Lafayette, Indiana (United States)

    2011-07-01

    Droplet entrainment and deposition are the two most important physical phenomena in the gas-liquid annular two-phase flow. Modeling of these phenomena is essential for the estimation of dryout margins in the Light Water Reactors (LWRs) and the boilers. In this study, gas-liquid annular two-phase flow experiments are performed in a vertical round tube test section under adiabatic conditions. Air-water and organic fluid Freon-113 are used as the test fluids. The experiments covered a wide range of pressure and flow conditions. Liquid film extraction technique was used for the measurement of droplet entrainment and deposition rates. Additionally, the thickness of liquid film was measured in the air-water experiments using the ring type conductance probes. In this paper, the experimental data on entrainment rate is used to analyze the currently available correlations in the literature. The analysis showed that the existing correlations failed to predict the data at high gas velocity conditions. At high gas velocity, the experimental entrainment rate approaches a maximum limiting value; however, the correlations predicted continuously increasing entrainment rate as the gas velocity increases. (author)

  18. Performance of annular flow sterilizer irradiated by a germicidal lamp

    Energy Technology Data Exchange (ETDEWEB)

    Sugawara, T.; Yoneya, M.; Ohashi, H. (Akita Univ. (Japan))

    1981-10-01

    Theoretical and experimental studies were conducted on the UV-inactivation characteristics of Bacillus subtilis spores in an annular-flow sterilizer irradiated by a germicidal lamp located at the center of the inner tube. Experimental results for sterilizer performance in laminar spore-suspension flow were well simulated dynamically and statically by theoretical considerations which incorporated multi-targets with single-hit model for the UV-inactivation kinetic and the diffuse light model for the angle characteristic of lamp, along with due attention to the parabolic velocity distribution and the negligible diffusion of spores. Scale on the outside wall of the inner tube was checked by the use of a cylindrical chemical actinometer. Calculated examples elucidate the reason why careful inspection is needed of UV-inactivation kinetics, angle characteristics of lamp, and fluid mixing to evaluate performance of actual flow UV sterilizers at high extent of inactivation up to the order of 99.999%.

  19. Understanding Wave-mean Flow Feedbacks and Tropospheric Annular Variability

    Science.gov (United States)

    Lorenz, D. J.

    2016-12-01

    The structure of internal tropospheric variability is important for determining the impact of the stratosphere on the troposphere. This study aims to better understand the fundamental dynamical mechanisms that control the feedbacks between the eddies and the mean flow, which in turn select the tropospheric annular mode. Recent work using Rossby Wave Chromatography suggests that "barotropic processes", which directly impact the meridional propagation of wave activity (specifically the reflectivity of the poleward flank of the mid-latitude jet), are more important for the positive feedback between the annular mode and the eddies than "baroclinic processes", which involve changes in the generation of wave activity by baroclinic instability. In this study, experiments with a fully nonlinear quasi-geostrophic model are discussed which provide independent confirmation of the importance of barotropic versus baroclinic processes. The experiments take advantage of the steady-state balance at upper-levels between the meridional gradient in diabatic heating and the second derivative of the upper-level EP flux divergence. Simulations with standard Newtonian heating are compared to simulations with constant-in-time heating taken from the climatology of the standard run and it is found that the forced annular mode response to changes in surface friction is very similar. Moreover, as expected from the annular mode response, the eddy momentum fluxes are also very similar. This is despite the fact that the upper-level EP flux divergence is very different between the two simulations (upper-level EP flux divergence must remain constant in the constant heating simulation while in the standard simulation there is no such constraint). The upper-level balances are maintained by a large change in the baroclinic wave source (i.e. vertical EP flux), which is accompanied by little momentum flux change. Therefore the eddy momentum fluxes appear to be relatively insensitive to the wave

  20. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference betwe

  1. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference

  2. An analytical model for annular flow boiling heat transfer in microchannel heat sinks

    Energy Technology Data Exchange (ETDEWEB)

    Megahed, A.; Hassan, I. [Concordia University, Montreal, QC (Canada). Dept. of Mechanical and Industrial Engineering

    2009-07-01

    An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)

  3. On the Motion of an Annular Film in Microgravity Gas-Liquid Flow

    Science.gov (United States)

    McQuillen, John B.

    2002-01-01

    Three flow regimes have been identified for gas-liquid flow in a microgravity environment: Bubble, Slug, and Annular. For the slug and annular flow regimes, the behavior observed in vertical upflow in normal gravity is similar to microgravity flow with a thin, symmetrical annular film wetting the tube wall. However, the motion and behavior of this film is significantly different between the normal and low gravity cases. Specifically, the liquid film will slow and come to a stop during low frequency wave motion or slugging. In normal gravity vertical upflow, the film has been observed to slow, stop, and actually reverse direction until it meets the next slug or wave.

  4. Characterization of annular two-phase gas-liquid flows in microgravity

    Science.gov (United States)

    Bousman, W. Scott; Mcquillen, John B.

    1994-01-01

    A series of two-phase gas-liquid flow experiments were developed to study annular flows in microgravity using the NASA Lewis Learjet. A test section was built to measure the liquid film thickness around the perimeter of the tube permitting the three dimensional nature of the gas-liquid interface to be observed. A second test section was used to measure the film thickness, pressure drop and wall shear stress in annular microgravity two-phase flows. Three liquids were studied to determine the effects of liquid viscosity and surface tension. The result of this study provide insight into the wave characteristics, pressure drop and droplet entrainment in microgravity annular flows.

  5. Stability of three-layered core-annular flow

    Science.gov (United States)

    Pillai, Dipin; Pushpavanam, Subramaniam; Sundararajan, T.

    2016-11-01

    Stability of a three-layered core-annular flow is analyzed using the method of modal linear stability analysis. A temporal analysis shows that the flow becomes unstable to two modes of instability when inertial effects are negligible. An energy budget analysis reveals that these two modes correspond to capillary instability associated with each fluid-fluid interface. With an increase in Reynolds number, the system exhibits additional Reynolds stress modes of instabilities. These modes correspond to the Tollmien-Schlichting type of waves associated with high Reynolds number shear flows, and are considered precursor to transition to turbulence. An investigation of the parameter space reveals that the system may simultaneously show up to 5 distinct modes of instability, viz., the two capillary modes at each interface and three Reynolds stress modes in the bulk of each phase. In addition, a spatio-temporal analysis shows that the Reynolds stress modes are always convectively unstable whereas the capillary modes may undergo a transition from convective to absolute instability with decrease in Weber number. To obtain encapsulated droplets in experiments, the operating parameters must be chosen such that the system lies in the regime of convective instability. MHRD-Govt of India, NSF 0968313.

  6. 3-D NUMERICAL STUDY AND COMPARISON OF ECCENTRIC AND CONCENTRIC ANNULAR-FINNED TUBE HEAT EXCHANGERS

    Directory of Open Access Journals (Sweden)

    FAROUK TAHROUR

    2015-11-01

    Full Text Available The use of 3-D computational fluid dynamics (CFD is proposed to simulate the conjugate conduction-convection of heat transfer problems in eccentric annularfinned tube heat exchangers. The numerical simulation results allow us to evaluate the heat transfer coefficient over fin surfaces, the fin efficiency and the pressure drop. The aim of the present paper is to determine the optimum tube position in the circular fin that maximizes heat dissipation and minimizes pressure drop. In addition, this study analyzes the effects of fin spacing and fin tube diameter on heat transfer and flow characteristics for a range of Reynolds numbers, 4500≤Re≤22500. A satisfactory qualitative and quantitative agreement was obtained between the numerical predictions and the results published in the literature. For small fin spacings, the eccentric annular finned tube is more efficient than the concentric one. Among the cases examined, the average heat transfer coefficient of the eccentric annular-finned tube, for a tube shift St =12 mm and a Reynolds number Re = 9923, was 7.61% greater than that of the concentric one. This gain is associated with a 43.09% reduction in pressure drop.

  7. Friction factor of annular Poiseuille flow in a transitional regime

    Directory of Open Access Journals (Sweden)

    Takahiro Ishida

    2016-12-01

    Full Text Available Annular Poiseuille flows in a transitional regime were investigated by direct numerical simulations with an emphasis on turbulent statistics including the friction factor that are affected by the presence of large-scale transitional structures. Five different radius ratios in the range of 0.1–0.8 and several friction Reynolds numbers in the range of 48–150 were analyzed to consider various flow states accompanied by characteristic transitional structures. Three characteristic structures, namely, turbulent–laminar coexistence referred to as “(straight puff,”“helical puff,” and “helical turbulence” were observed. The selection of the structures depends on both the radius ratio and the Reynolds number. The findings indicated that despite the transitional state with a turbulent–laminar coexistence, the helical turbulence resulted in a friction factor that was as high as the fully turbulent value. In contrast, with respect to the occurrence of streamwise-finite transitional structures, such as straight/helical puffs, the friction factor decreased in a stepwise manner toward a laminar level. The turbulent statistics revealed asymmetric distributions with respect to the wall-normal direction wherein the profiles and magnitudes were significantly influenced by the occurrence of transitional structures.

  8. Flow Pressure Loss through Straight Annular Corrugated Pipes

    Science.gov (United States)

    Sargent, Joseph R.; Kirk, Daniel R.; Marsell, Brandon; Roth, Jacob; Schallhorn, Paul A.; Pitchford, Brian; Weber, Chris; Bulk, Timothy

    2016-01-01

    Pressure loss through annular corrugated pipes, using fully developed gaseous nitrogen representing purge pipes in spacecraft fairings, was studied to gain insight into a friction factor coefficient for these pipes. Twelve pipes were tested: four Annuflex, four Masterflex and two Titeflex with ¼”, 3/8”, ½” and ¾” inner diameters. Experimental set-up was validated using smooth-pipe and showed good agreement to the Moody diagram. Nitrogen flow rates between 0-200 standard cubic feet per hour were used, producing approximate Reynolds numbers from 300-23,000. Corrugation depth varied from 0.248 = E/D = 0.349 and relative corrugation pitch of 0.192 = P/D = 0.483. Differential pressure per unit length was measured and calculated using 8-9 equidistant pressure taps. A detailed experimental uncertainty analysis, including correlated bias error terms, is presented. Results show larger differential pressure losses than smooth-pipes with similar inner diameters resulting in larger friction factor coefficients.

  9. Visual Measurements of Droplet Size in Gas Liquid Annular Flow

    Energy Technology Data Exchange (ETDEWEB)

    Fore, L.B.; Ibrahim, B.B.; Beus, S.G.

    2000-07-01

    Drop size distributions have been measured for nitrogen-water annular flow in a 9.67 mm hydraulic diameter duct, at system pressures of 3.4 and 17 atm and a temperature of 38 C. These new data extend the range of conditions represented by existing data in the open literature, primarily through an increase in system pressure. Since most existing correlations were developed from data obtained at lower pressures, it should be expected that the higher-pressure data presented in this paper would not necessarily follow those correlations. The correlation of Tatterson, et al. (1977) does not predict the new data very well, while the correlation of Kataoka, et al. (1983) only predicts those data taken at the lower pressure of 3.4 atm. However, the maximum drop size correlation of Kocamustafaogullari, et al. (1994) does predict the current data to a reasonable approximation. Similarly, their correlation for the Sauter mean diameter can predict the new data, provided the coefficient in the equation is adjusted.

  10. Analytical and numerical study of the electro-osmotic annular flow of viscoelastic fluids.

    Science.gov (United States)

    Ferrás, L L; Afonso, A M; Alves, M A; Nóbrega, J M; Pinho, F T

    2014-04-15

    In this work we present semi-analytical solutions for the electro-osmotic annular flow of viscoelastic fluids modeled by the Linear and Exponential PTT models. The viscoelastic fluid flows in the axial direction between two concentric cylinders under the combined influences of electrokinetic and pressure forcings. The analysis invokes the Debye-Hückel approximation and includes the limit case of pure electro-osmotic flow. The solution is valid for both no slip and slip velocity at the walls and the chosen slip boundary condition is the linear Navier slip velocity model. The combined effects of fluid rheology, electro-osmotic and pressure gradient forcings on the fluid velocity distribution are also discussed.

  11. Classification of annular bed flow patterns and investigation on their influence on the bottom spray fluid bed coating process.

    Science.gov (United States)

    Wang, Li Kun; Heng, Paul Wan Sia; Liew, Celine Valeria

    2010-05-01

    This study aims to classify annular bed flow patterns in the bottom spray fluid bed coating process, study their influence on coat uniformity and investigate the feasibility of developing real-time annular bed flow pattern detection as a PAT tool. High-speed imaging and particle image velocimetry were used to visualize annular bed flow. Color coating and subsequent tristimulus colorimetry were employed to determine influence of annular bed flow pattern on coat uniformity. Feasibility of monitoring annular bed flow pattern through an observation window was tested using miniaturized particle velocity field and time series particle velocity orientation information. Three types of annular bed flow patterns were identified. Plug flow gave the best coat uniformity followed by global and localized fluidization. Plug flow may be advantageous for high spray-rate conditions, large-scale coating and prevention of particle segregation. Plug flow could be differentiated from the other flow patterns through a simulated observation window. Annular bed flow patterns were classified and found to influence particle coat uniformity noticeably. Availability of annular bed flow information for large-scale coaters would enable adjustments for process optimization. This study highlights the potential of monitoring annular bed flow pattern as a PAT tool.

  12. Forced convection to laminar flow of liquid egg yolk in circular and annular ducts

    Directory of Open Access Journals (Sweden)

    M. Bernardi

    2009-06-01

    Full Text Available The steady-state heat transfer in laminar flow of liquid egg yolk - an important pseudoplastic fluid food - in circular and concentric annular ducts was experimentally investigated. The average convection heat transfer coefficients, determined by measuring temperatures before and after heating sections with constant temperatures at the tube wall, were used to obtain simple new empirical expressions to estimate the Nusselt numbers for fully established flows at the thermal entrance of the considered geometries. The comparisons with existing correlations for Newtonian and non-Newtonian fluids resulted in excellent agreement. The main contribution of this work is to supply practical and easily applicable correlations, which are, especially for the case of annulus, rather scarce and extensively required in the design of heat transfer operations dealing with similar shear-thinning products. In addition, the experimental results may support existing theoretical analyses.

  13. Experimental investigation of three-dimensional flow structures in annular swirling jets

    NARCIS (Netherlands)

    Percin, M.; Vanierschot, M.; Van Oudheusden, B.W.

    2015-01-01

    Annular jet flows are of practical interest in view of their occurrence in many industrial applications in the context of bluff-body combustors [1]. They feature different complex flow characteristics despite their simple geometry: a central recirculation zone (CRZ) as a result of flow separation be

  14. Experimental investigation on Heat Transfer Performance of Annular Flow Path Heat Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)

    2015-05-15

    Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heat pipe design cases was studied to determine the heat pipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heat pipes, and the transient performance of high temperature sodium heat pipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heat pipes cooling system using loop heat pipes for decay heat removal cooling and analysis of heat pipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heat pipe is the combination of the heat pipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heat pipe containing neutron absorber material, B{sub 4}C. The main objective is to investigate the effect of the inner structure in heat pipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B{sub 4}C pellet as cylindrical structures. The thermal performances of each heat pipes were measured experimentally. Among them, concentric heat pipe showed the best performance compared with others. 1. Annular evaporation section heat pipe and annular flow path heat pipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer

  15. The linear and nonlinear stability of thread-annular flow.

    Science.gov (United States)

    Walton, Andrew G

    2005-05-15

    The surgical technique of thread injection of medical implants is modelled by the axial pressure-gradient-driven flow between concentric cylinders with a moving core. The linear stability of the flow to both axisymmetric and asymmetric perturbations is analysed asymptotically at large Reynolds number, and computationally at finite Reynolds number. The existence of multiple regions of instability is predicted and their dependence upon radius ratio and thread velocity is determined. A discrepancy in critical Reynolds numbers and cut-off velocity is found to exist between experimental results and the predictions of the linear theory. In order to account for this discrepancy, the high Reynolds number, nonlinear stability properties of the flow are analysed and a nonlinear, equilibrium critical layer structure is found, which leads to an enhanced correction to the basic flow. The predictions of the nonlinear theory are found to be in good agreement with the experimental data.

  16. Numerical Simulations of Thermocapillary Flow of a Binary Mixture with the Soret Effect in a Shallow Annular Pool

    Science.gov (United States)

    Yu, Jia-Jia; Zhang, Li; Li, You-Rong; Chen, Jie-Chao

    2016-04-01

    In order to understand the characteristics of thermocapillary flow of a toluene/ n-hexane mixture with the Soret effect in a shallow annular pool, a series of three-dimensional numerical simulations were carried out. The shallow annular pool was heated from the outer cylinder and cooled at the inner cylinder. The initial toluene concentration in the toluene/ n-hexane mixture varied from 0 to 0.4467. Results indicate that the flow undergoes two transitions from the axisymmetric steady flow to the hydrothermal waves, and then to chaos with the increase of the thermocapillary Reynolds number. The critical thermocapillary Reynolds number for the incipience of the oscillatory flow decreases with the increase of the initial solute concentration. When the thermocapillary flow transits to a three-dimensional oscillatory flow, a concentration fluctuation is observed on the free surface, which is similar to the hydrothermal waves. However, compared with that of the temperature, the dimensionless fluctuation amplitude of the concentration is relatively weak. Furthermore, the fundamental oscillation frequency increases linearly with the initial solute concentration, but the wave number of the hydrothermal waves is almost unchangeable.

  17. Heat transfer of bubbly flow on inner wall of annular channel

    Directory of Open Access Journals (Sweden)

    Lobanov Pavel

    2017-01-01

    Full Text Available Experimental investigations of heat transfer from the heated wall to the two-phase bubbly flow were performed in vertical annular channel using air-water system. The IR-thermography and miniature temperature sensors were used to measure heat transfer coefficients. The influence of bubbles on heat transfer is shown in comparison with the case of single phase flow. The presence of bubbles in the flow leads to heat transfer intensification in the annular channel even for low void fractions.

  18. The benign concentric annular macular dystrophy locus maps to 6p12.3-q16.

    NARCIS (Netherlands)

    Lith-Verhoeven, J.J. van; Hoyng, C.B.; Helm, B. van den; Deutman, A.F.; Brink, H.M.A.; Kemperman, M.H.; Jong, W.H. de; Kremer, J.M.J.; Cremers, F.P.M.

    2004-01-01

    PURPOSE: To describe the clinical findings and to identify the genetic locus in a Dutch family with autosomal dominant benign concentric annular macular dystrophy (BCAMD). METHODS: All family members underwent ophthalmic examination. Linkage analysis of candidate retinal dystrophy loci and a whole g

  19. Droplets in annular-dispersed gas-liquid pipe-flows

    NARCIS (Netherlands)

    Van 't Westende, J.M.C.

    2008-01-01

    Annular-dispersed gas-liquid pipe-flows are commonly encountered in many industrial applications, and have already been studied for many decades. However, due to the great complexity of this type of flow, there are still many phenomena that are poorly understood. The aim of this thesis is to shed mo

  20. THE PERTURBATION SOLUTIONS OF THE FLOW IN A ROTATING CURVED ANNULAR PIPE

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, the flow in a rotating curved annular pipe isexamined by a perturbation method. A second order perturbation solution is presented. The characteristics of the secondary flow and the axial flow are studied in detail.The study indicates that the loops of the secondary flow are more complex than those in a curved annular pipe without rotation and its numbers depend on the ratio of the Coriolis force to centrifugal force F. As F ≈- 1 , the secondary flow has eight loops and its intensity reaches the minimum value, and the distribution of the axial flow is like that of the Poiseuille flow. The position of the maximum axial velocity is pushed to either outer bend or inner bend, which is also determined by F.

  1. Trichophyton tonsurans infection manifesting as multiple concentric annular erythemas.

    Science.gov (United States)

    Ouchi, Takeshi; Nagao, Keisuke; Hata, Yasuki; Otuka, Tomoko; Inazumi, Toyoko

    2005-07-01

    We report a case of dermatophytosis in a Judo wrestler caused by Trichophyton tonsurans (T. tonsurans) with clinical features that mimicked the concentric rings of tinea imbricata. Tinea imbricata is a unique dermatophytosis caused by Trichophyton concentricum (T. concentricum), observed endemically in subtropical to torrid zones and characterized by impressive concentric rings. We found three similar cases of the dermatophytosis in the literature that were reported as tinea pseudoimbricata or tinea indecisiva. All of these cases were associated with systemic or local immunosuppression, perhaps simulating the mechanism of tinea imbricata, which is known to involve the lack of delayed type hypersensitivity to T. concentricum. These cases imply that iatrogenic immunosuppression may perhaps play an important role in the development of the unique clinical features mimicking tinea imbricata. Furthermore, three of the four cases, including the presented case, were caused by T. tonsurans. It may be necessary to consider T. tonsurans infection when multiple concentric erythemas are encountered.

  2. On the levitation force in horizontal core-annular flow with a large viscosity ratio and small density ratio

    NARCIS (Netherlands)

    Ooms, G.; Pourquie, M.J.B.M.; Beerens, J.C.

    2013-01-01

    A numerical study has been made of horizontal core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question how the buoyancy force on the core, caused by a density difference between

  3. Thermal-solutal capillary-buoyancy flow of a low Prandtl number binary mixture with a -1 capillary ratio in an annular pool

    Science.gov (United States)

    Yu, Jia-Jia; Wu, Chun-Mei; Li, You-Rong; Chen, Jie-Chao

    2016-08-01

    A series of three-dimensional numerical simulations on thermal-solutal capillary-buoyancy flow in an annular pool were carried out. The pool was filled with silicon-germanium melt with an initial silicon mass fraction of 1.99%. The Prandtl number and the Lewis number of the working fluid are 6.37 × 10-3 and 2197.8, respectively. Both the radial temperature gradient and the solute concentration gradient were applied to the annular pool. The capillary ratio was assumed to be -1, which means that the solutal and thermal capillary effects were equal and opposite. Results show that the thermal-solutal capillary-buoyancy flow always occurs at this special case with the capillary ratio of -1, and even in a shallow annular pool with an aspect ratio of 0.05. With the increase of the thermal Marangoni number, four kinds of flow patterns appear orderly, including concentric rolls, petal-like, spoke, and rosebud-like patterns. These flow patterns are strongly influenced by the local interaction between the solutal and thermal capillary effects and the vertical solute concentration gradient near the outer cylinder. A small vortex driven by the dominant solutal capillary effect emerges near the inner cylinder, which is different from the flow pattern in a pure fluid. In addition, the critical thermal Marangoni number of the initial three-dimensional flow decreases with the increase of the aspect ratio of the annular pool.

  4. Intermittent Flow of Granular Matter in an Annular Geometry

    Science.gov (United States)

    Brzinski, Ted; Daniels, Karen E.

    Granular solids can be subjected to a finite stress below which the response is elastic. Above this yield stress, however, the material fails catastrophically, undergoing a rapid plastic deformation. In the case of a monotonically increasing stress the material exhibits a characteristic stick-slip response. We investigate the statistics of this intermittent failure in an annular shear geometry, driven with a linear-ramp torque in order to generate the stick-slip behavior. The apparatus is designed to allow visual access to particle trajectories and inter-particle forces (through the use of photoelastic materials). Additionally, twelve piezoelectric sensors at the outer wall measure acoustic emissions due to the plastic deformation of the material. We vary volume fraction, and use both fixed and deformable boundaries. We measure how the distribution of slip size and duration are related to the bulk properties of the packing, and compare to systems with similar governing statistics.

  5. Thermal hydraulic analysis of the annular flow helium heater design

    Science.gov (United States)

    Chen, N. C.; Sanders, J. P.

    1982-05-01

    Core support performance test (CSPT) by use of an existing facility, components flow test loop (CFTL), as part of the high temperature gas cooled reactor (HTGR) application program were conducted. A major objective of the CSPT is to study accelerated corrosion of the core graphite support structure in helium at reactor conditions. Concentration of impurities will be adjusted so that a 6 month test represents the 30 year reactor life. Thermal hydraulic and structural integrity of the graphite specimen, will be studied at high pressure of 7.24 MPa (1050 psi) and high temperature of 1000 deg C in a test vessel. To achieve the required high temperature at the test section, a heater bundle has to be specially designed and properly manufactured. Performance characteristics of the heater which were determined from an analysis based on this design are presented.

  6. Annular flow of cement slurries; Escoamento anular de pastas de cimento

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Maria das Gracas Pena; Martins, Andre Leibsohn; Oliveira, Antonio Augusto J. de [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas. Setor de Tecnologia de Perfuracao

    1989-12-31

    This paper considers the analysis of laminar, transitory and turbulent flow regimes of cement slurries of various compositions flowing in annular sections. It is an experimental study to evaluate the performance of dozens of equations found in the literature that reflect the rheological behavior of non-Newtonian fluids, the dimensioning of annular sections, the delimitation of the transitory zone and the estimative of friction losses in the turbulent flow regime. A large-scale physical simulator (SHS-Surface Hydraulic Simulator), was designed and constructed at the PETROBRAS Research Center in order to obtain flow parameters. A computer program capable of analysing and drawing conclusions from the behavior of non-Newtonian fluids flowing in different geometries and energetic conditions was also developed. These were considered as essential stages for the development of the project. (author) 17 refs., 9 figs., 18 tabs.

  7. Concentric Split Flow Filter

    Science.gov (United States)

    Stapleton, Thomas J. (Inventor)

    2015-01-01

    A concentric split flow filter may be configured to remove odor and/or bacteria from pumped air used to collect urine and fecal waste products. For instance, filter may be designed to effectively fill the volume that was previously considered wasted surrounding the transport tube of a waste management system. The concentric split flow filter may be configured to split the air flow, with substantially half of the air flow to be treated traveling through a first bed of filter media and substantially the other half of the air flow to be treated traveling through the second bed of filter media. This split flow design reduces the air velocity by 50%. In this way, the pressure drop of filter may be reduced by as much as a factor of 4 as compare to the conventional design.

  8. Droplet entrainment correlation in vertical upward co-current annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Pravin [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States)], E-mail: psawant@purdue.edu; Ishii, Mamoru [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States); Mori, Michitsugu [Tokyo Electric Power Co., Inc., R and D Center, 4-1 Egasaki-cho, Tsurumi-ku, Yokohama 230-8510 (Japan)], E-mail: michitsugu.mori@tepco.co.jp

    2008-06-15

    Upward annular two-phase flow in a vertical tube is characterized by the presence of liquid film on the tube wall and entrained droplet laden gas phase flowing through the tube core. Entrainment fraction in annular flow is defined as a fraction of the total liquid flow flowing in the form of droplets through the central gas core. Its prediction is important for the estimation of pressure drop and dryout in annular flow. In the following study, measurements of entrainment fraction have been obtained in vertical upward co-current air-water annular flow covering wide ranges of pressure and flow conditions. Comparison of the experimental data with the existing entrainment fraction prediction correlations revealed their inadequacies in simulating the trends observed under high flow and high pressure conditions. Furthermore, several correlations available in the literature are implicit and require iterative calculations. Analysis of the experimental data showed that the non-dimensional numbers, Weber number (We = {rho}{sub g}{sup 2}D/{sigma}({delta}{rho}/{rho}{sub g}){sup 1/4}) and liquid phase Reynolds number (Re{sub f} = {rho}{sub f}D/{mu}{sub f}), successfully collapse the data. In view of this, simple, explicit correlation was developed based on these non-dimensional numbers for the prediction of entrainment fraction. The new correlation successfully predicted the trends under the high flow and high pressure conditions observed in the current experimental data and the data available in open literature. However, in order to use the proposed correlation it is necessary to predict the maximum possible entrainment fraction (or limiting entrainment fraction). In the current analysis, an experimental data based correlation was used for this purpose. However, a better model or correlation is necessary for the maximum possible entrainment fraction. A theoretical discussion on the mechanism and modeling of the maximum possible entrainment fraction

  9. Modeling of annular two-phase flow using a unified CFD approach

    Energy Technology Data Exchange (ETDEWEB)

    Li, Haipeng, E-mail: haipengl@kth.se; Anglart, Henryk, E-mail: henryk@kth.se

    2016-07-15

    Highlights: • Annular two-phase flow has been modeled using a unified CFD approach. • Liquid film was modeled based on a two-dimensional thin film assumption. • Both Eulerian and Lagrangian methods were employed for the gas core flow modeling. - Abstract: A mechanistic model of annular flow with evaporating liquid film has been developed using computational fluid dynamics (CFD). The model is employing a separate solver with two-dimensional conservation equations to predict propagation of a thin boiling liquid film on solid walls. The liquid film model is coupled to a solver of three-dimensional conservation equations describing the gas core, which is assumed to contain a saturated mixture of vapor and liquid droplets. Both the Eulerian–Eulerian and the Eulerian–Lagrangian approach are used to describe the droplet and vapor motion in the gas core. All the major interaction phenomena between the liquid film and the gas core flow have been accounted for, including the liquid film evaporation as well as the droplet deposition and entrainment. The resultant unified framework for annular flow has been applied to the steam-water flow with conditions typical for a Boiling Water Reactor (BWR). The simulation results for the liquid film flow rate show good agreement with the experimental data, with the potential to predict the dryout occurrence based on criteria of critical film thickness or critical film flow rate.

  10. Fully developed MHD natural convection flow in a vertical annular microchannel: An exact solution

    Directory of Open Access Journals (Sweden)

    Basant K. Jha

    2015-07-01

    Full Text Available An exact solution of steady fully developed natural convection flow of viscous, incompressible, electrically conducting fluid in a vertical annular micro-channel with the effect of transverse magnetic field in the presence of velocity slip and temperature jump at the annular micro-channel surfaces is obtained. Exact solution is expressed in terms of modified Bessel function of the first and second kind. The solution obtained is graphically represented and the effects of radius ratio (η, Hartmann number (M, rarefaction parameter (βvKn, and fluid–wall interaction parameter (F on the flow are investigated. During the course of numerical computations, it is found that an increase in Hartmann number leads to a decrease in the fluid velocity, volume flow rate and skin friction. Furthermore, it is found that an increase in curvature radius ratio leads to an increase in the volume flow rate.

  11. Steady thermal——solutal capillary convection in a shallow annular pool with the radial temperature and concentration gradients

    Institute of Scientific and Technical Information of China (English)

    LI YouRong; GONG ZhenXing; WU ChunMei; WU ShuangYing

    2012-01-01

    Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the free surface.The pool is heated from the outer cylinder with high solutal concentration and cooled at the inner cylinder with low solutal concentration.The asymptotic solution is obtained in the core region in the limit as the aspect ratio,which is defined as the ratio of the depth to the width of the pool,goes to zero.The comparison with the previous work certifies that the asymptotic solution is right and believable.The influences of the solutal capillary force,the buoyant force,the Soret effect and the geometric parameters on the fluid flow are analyzed.

  12. Effects of Nonuniform Blade Pitch on the Flow Through an Annular Turbine Nozzle

    OpenAIRE

    1995-01-01

    This paper discusses flow measurement results both upstream and downstream of a transonic annular gas turbine nozzle with a nonuniform pitch. The downstream measurements are performed in the plane where the leading edge of the rotor blade is located in the gas turbine. The experiments were performed using total pressure probes and wall static pressure taps. The pitch variation modifies the flow field both upstream and downstream of the nozzle, although the experiments show that the effect ...

  13. Displacement of one Newtonian fluid by another: density effects in axial annular flow

    DEFF Research Database (Denmark)

    Szabo, Peter; Hassager, Ole

    1997-01-01

    . Comparison with a simple theory for drainage of thin films is performed. It is found that recirculations deform the fluid-fluidinterface significantly in situations dominated by buoyancy forces. Also, a deviation from the concentric annular geometry is shown to induce azimuthal transport of fluid. Finally...

  14. LDA measurement of the passage flow field in an annular airfoil cascade

    Science.gov (United States)

    Stauter, R. C.; Fleeter, S.

    1987-01-01

    Models to predict the complex three-dimensional flow through turbomachine blade rows are being developed. To verify these models and direct necessary refinements, it is necessary that predictions be correlated with data obtained in experiments which model the fundamental three-dimensional blade row flow phenomena. This paper describes a series of experiments performed in a large scale, subsonic, annular cascade facility specifically designed to provide such data. In particular, the effect of incidence angle on the three-dimensional passage flow field through an annular cascade of cambered airfoils is investigated and quantified, accomplished by obtaining detailed and expensive LDA data. These data demonstrate and quantify the development of the passage vortices through the airfoil passage and their strong interaction with the endwall boundary layers.

  15. Core-annular miscible two-fluid flow in a slippery pipe: A stability analysis

    Science.gov (United States)

    Chattopadhyay, Geetanjali; Usha, Ranganathan; Sahu, Kirti Chandra

    2017-09-01

    This study is motivated by the preliminary direct numerical simulations in double-diffusive (DD) core-annular flows with slip at the wall which displayed elliptical shaped instability patterns as in a rigid pipe case; however, slip at the pipe wall delays the onset of instability for a range of parameters and increases the phase speed. This increased our curiosity to have a thorough understanding of the linear stability characteristics of the miscible DD two-fluid flow in a pipe with slip at the pipe wall. The present study, therefore, addresses the linear stability of viscosity-stratified core-annular Poiseuille flow of miscible fluids with matched density in a slippery pipe in the presence of two scalars diffusing at different rates. The physical mechanisms responsible for the occurrence of instabilities in the DD system are explained through an energy budget analysis. The differences and similarities between core-annular flow in a slippery pipe and in a plane channel with velocity slip at the walls are explored. The stability characteristics are significantly affected by the presence of slip. The diffusivity effect is non-monotonic in a DD system. A striking feature of instability is that only a band of wavenumbers is destabilized in the presence of moderate to large inertial effects. Both the longwave and shortwave are stabilized at small Reynolds numbers. Slip exhibits a dual role of stabilizing or destabilizing the flow. The preliminary direct numerical simulations confirm the predictions of the linear stability analysis. The present study reveals that it may be possible to control the instabilities in core-annular pressure driven pipe flows by imposing a velocity slip at the walls.

  16. High pressure annular two-phase flow in a narrow duct. Part 1: Local measurements in the droplet field, and Part 2: Three-field modeling

    Energy Technology Data Exchange (ETDEWEB)

    Trabold, T.A.; Kumar, R. [Lockheed Martin Corp., Schenectady, NY (United States)

    1999-07-01

    In Part 1, detailed measurements were made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the droplet profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional {lambda}-shaped waves appear in annular flows for high flow rates. Part 2 outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with

  17. Prediction of amount of entrained droplets in vertical annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Pravin [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States)], E-mail: psawant@purdue.edu; Ishii, Mamoru [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States)], E-mail: ishii@purdue.edu; Mori, Michitsugu [Tokyo Electric Power Co. Inc., 4-1 Egasaki-cho, Tsurumi-ku, Yokohama 230-8510 (Japan)], E-mail: michitsugu.mori@tepco.co.jp

    2009-08-15

    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 experiment, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using the liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant [Sawant, P.H., Ishii, M., Mori, M., 2008. Droplet entrainment correlation in vertical upward co-current annular two-phase flow. Nucl. Eng. Des. 238 (6), 1342-1352] 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 [Willetts, I.P., 1987. Non-aqueous annular two-phase flow. D.Phil. Thesis, University of Oxford]. However, comparison of the correlations with the steam-water data available in literature showed significant discrepancies. It is proposed that these discrepancies might have been caused due to the inadequacy of the liquid film extraction method used to measure the entrainment

  18. Surface tension effects on vertical upward annular flows in a small diameter pipe

    Energy Technology Data Exchange (ETDEWEB)

    Sadatomi, Michio, E-mail: sadatomi@mech.kumamoto-u.ac.jp [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Kawahara, Akimaro [Dept. of Advanced Mechanical Systems, Kumamoto Univ., 39-1, Kurokami 2-chome, Chuou-ku, Kumamoto 860-8555 (Japan); Suzuki, Aruta [Plant Design & Engineering Dept., Environment, Energy & Plant Headquarters, Hitachi Zosen Corporation, 7-89, Nankokita 1-chome, Suminoe-ku, Osaka, 559-8559 (Japan)

    2016-12-15

    Highlights: • Surface tension effects were clarified on annular flow in a small diameter pipe. • The mean liquid film thickness became thinner with decreasing of surface tension. • The liquid droplet fraction and the interfacial shear stress became higher with it. • New prediction methods for the above parameters were developed and validated. - Abstract: Experiments were conducted to study the surface tension effects on vertical upward annular flows in a 5 mm I.D. pipe using water and low surface tension water with a little surfactant as the test liquid and air as the test gas. Firstly, the experimental results on the mean liquid film thickness, the liquid droplet fraction and the interfacial shear stress in annular flows together with some flow pictures are presented to clarify the surface tension effects. From these, the followings are clarified: In the low surface tension case, the liquid film surface becomes rough, the liquid film thickness thin, the liquid droplet fraction high, and the interfacial shear stress high. Secondary, correlations in literatures for the respective parameters are tested against the present data. The test results show that no correlation for the respective parameters could predict well the present data. Thus, correlations are revised by accounting for the surface tension effects. The results of the experiments, the correlations tests and their revisions mentioned above are presented in the present paper.

  19. Annular multiphase flow behavior during deep water drilling and the effect of hydrate phase transition

    Institute of Scientific and Technical Information of China (English)

    Wang Zhiyuan; Sun Baojiang

    2009-01-01

    It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.

  20. Control of the flow in the annular region of a shrouded cylinder with splitter plate

    Directory of Open Access Journals (Sweden)

    Ozkan Gokturk Memduh

    2017-01-01

    Full Text Available In the present study, the flow control with a splitter plate was studied considering the annular region of a shrouded cylinder. The effect of splitter plate angle, α which was defined according to the cylinder centreline is investigated experimentally in deep water using Particle image Velocimetry (PIV technique and flow visualization by dye injection method. The range of splitter plate angle was selected within 60°≤ α ≤180° with an increment of 30°. The porosity of the shroud which is a perforated cylinder was selected as β=0.7 in order to have larger fluid entrainment through the cylinder. The results were compared with the no-plate case and showed that the splitter plate located in the annular region of shrouded cylinders is effective on reducing the turbulence levels just behind the cylinder base, as well as the near wake of the perforated shroud.

  1. The effect of pressure on annular flow pressure drop in a small pipe

    Energy Technology Data Exchange (ETDEWEB)

    de Bertodano, M.A.L.; Beus, S.G.; Shi, Jian-Feng

    1996-09-01

    New experimental data was obtained for pressure drop and entrainment for annular up-flow in a vertical pipe. The 9.5 mm. pipe has an L/D ratio of 440 to insure fully developed annular flow. The pressure ranged from 140 kPa to 660 kPa. Therefore the density ratio was varied by a factor of four approximately. This allows the investigation of the effect of pressure on the interfacial shear models. Gas superficial velocities between 25 and 126 m/s were tested. This extends the range of previous data to higher gas velocities. The data were compared with well known models for interfacial shear that represent the state of the art. Good results were obtained when the model by Asali, Hanratty and Andreussi was modified for the effect of pressure. Furthermore an equivalent model was obtained based on the mixing length theory for rough pipes. It correlates the equivalent roughness to the film thickness.

  2. Experimental Study on the Characteristics of Liquid Layer and Disturbance Waves in Horizontal Annular Flow

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The mechanism for transporting liquid from the bottom of the pipe to the top still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow.To resolve this issue,using five parallel-wire conductance probes,time records of local liquid film thickness at five circumferential positions were collected.The characteristics of circumferential liquid film thickness profiles and its variation with gas and liquid velocities were obtained.The basic features of probability distribution function,probability density function,auto-correlation,cross-correlation and power spectrum density function of the disturbance waves in annular flow were studied respectively.The characterstics of circumferential profiles of disturbance waves and its variation with gas and liquid velocities were presented.

  3. SHAPE EFFECT OF ANNULAR CONCENTRATOR IN ULTRASONIC SYSTEM ON AMPLIFICATION FACTOR OF VIBRATIONS AMPLITUDE

    Directory of Open Access Journals (Sweden)

    D. A. Stepanenko

    2016-01-01

    Full Text Available The paper contains a theoretical underpinning on creation of ultrasonic vibration concentrators based on annular elastic elements with non-circular (ellipse-like eccentric shape of internal contour. Shape of internal contour in polar coordinates is described by Fourier series relative to angular coordinate that consists of a constant term and first and second harmonics. An effect of geometric parameters of the concentrator on amplification factor and natural vibration frequencies has been investigated with the help of a finite element method. The paper reveals the possibility to control an amplification factor of annular concentrators while varying eccentricity of internal contour and mean value of cross-section thickness. The amplification factor satisfies a condition K < N, where N is thickness ratio of amplifier input and output sections, and it is decreasing with increase of vibration mode order. The similar condition has been satisfied for conical bar concentrator with the difference that in the case of bar concentrators an amplification is ensured due to variation of diameter and N will represent ratio of diameters. It has been proved that modification of internal contour shape makes it possible to carry out a wide-band tuning of natural frequencies of concentrator vibrations without alteration of its overall dimensions and substantial change of amplification factor, which is important for frequency matching of the concentrator and ultrasonic vibratory system. Advantages of the proposed concentrators include simplicity of design and manufacturing, small overall dimensions, possibility for natural frequency tuning by means of static load variation. The developed concentrators can find their application in ultrasonic devices and instruments for technological and medical purposes.

  4. Flow Simulation of Supersonic Inlet with Bypass Annular Duct

    Science.gov (United States)

    Kim, HyoungJin; Kumano, Takayasu; Liou, Meng-Sing; Povinelli, Louis A.; Conners, Timothy R.

    2011-01-01

    A relaxed isentropic compression supersonic inlet is a new concept that produces smaller cowl drag than a conventional inlet, but incurs lower total pressure recovery and increased flow distortion in the (radially) outer flowpath. A supersonic inlet comprising a bypass annulus to the relaxed isentropic compression inlet dumps out airflow of low quality through the bypass duct. A reliable computational fluid dynamics solution can provide considerable useful information to ascertain quantitatively relative merits of the concept, and further provide a basis for optimizing the design. For a fast and reliable performance evaluation of the inlet performance, an equivalent axisymmetric model whose area changes accounts for geometric and physical (blockage) effects resulting from the original complex three-dimensional configuration is proposed. In addition, full three-dimensional calculations are conducted for studying flow phenomena and verifying the validity of the equivalent model. The inlet-engine coupling is carried out by embedding numerical propulsion system simulation engine data into the flow solver for interactive boundary conditions at the engine fan face and exhaust plane. It was found that the blockage resulting from complex three-dimensional geometries in the bypass duct causes significant degradation of inlet performance by pushing the terminal normal shock upstream.

  5. Properties of disturbance waves in vertical annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Pravin [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States)], E-mail: psawant@purdue.edu; Ishii, Mamoru [Purdue University, School of Nuclear Engineering, 400 Central Dr., West Lafayette, IN 47907-2017 (United States); Hazuku, Tatsuya; Takamasa, Tomoji [Faculty of Marine Technology, Tokyo University of Marine Science and Technology, Etchujima, Koto-ku, Tokyo 135-8533 (Japan); Mori, Michitsugu [Tokyo Electric Power Co., Inc., 4-1 Egasaki-cho, Tsurumi-ku, Yokohama 230-8510 (Japan)

    2008-12-15

    Disturbance waves play an important role in interfacial transfer of mass, momentum and energy in annular two-phase flow. In spite of their importance, majority of the experimental data available in literature on disturbance wave properties such as velocity, frequency, wavelength and amplitude are limited to near atmospheric conditions (Azzopardi, B.J., 1997. Drops in annular two-phase flow. International Journal of Multiphase Flow, 23, 1-53). In view of this, air-water annular flow experiments have been conducted at three pressure conditions (1.2, 4.0 and 5.8 bar) in a tubular test section having an inside diameter 9.4 mm. At each pressure condition liquid and gas phase flow rates are varied over a large range so that the effects of density ratio, liquid flow rate and gas flow rate on disturbance wave properties can be studied systematically. A liquid film thickness is measured by two flush mounted ring shaped conductance probes located 38.1 mm apart. Disturbance wave velocity, frequency, amplitude and wavelength are estimated from the liquid film thickness measurements by following the statistical analysis methods. Parametric trends in variations of disturbance wave properties are analyzed using the non-dimensional numbers; liquid phase Reynolds number (Re{sub f}), gas phase Reynolds number (Re{sub g}), Weber number (We) and Strouhal number (Sr). Finally, the existing correlations available for the prediction of disturbance wave velocity and frequency are analyzed and a new, improved correlation is proposed for the prediction of disturbance wave frequency. The new correlation satisfactorily predicted the current data and the data available in literature.

  6. Experimental research on dryout point of flow boiling in narrow annular channels

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An experimental research on the dryout point of flow boiling in narrow annular channels under low mass flux with 1.55 mm and 1.05 mm annular gap, respectively, is conducted. Distilled water is used as working fluid and the range of pressure is limited within 2.0~4.0 MPa and that of mass flux is 26.0~69.0 kg·m-2·s-1. The relation of critical heat flux (CHF) and critical qualities with mass flux and pressure are revealed. It is found that the critical qualities decrease with the increasing mass flux and increase with the increasing inlet qualities in externally heated annuli.Under the same conditions, critical qualities in the outer tube are always larger than those in the inner tube. The appearance of dryout point in bilaterally heated narrow annuli can be judged according to the ratio of qo/qi.

  7. Simulation of non-Newtonian oil-water core annular flow through return bends

    Science.gov (United States)

    Jiang, Fan; Wang, Ke; Skote, Martin; Wong, Teck Neng; Duan, Fei

    2017-07-01

    The volume of fluid (VOF) model is used together with the continuum surface force (CSF) model to numerically simulate the non-Newtonian oil-water core annular flow across return bends. A comprehensive study is conducted to generate the profiles of pressure, velocity, volume fraction and wall shear stress for different oil properties, flow directions, and bend geometries. It is revealed that the oil core may adhere to the bend wall under certain operating conditions. Through the analysis of the total pressure gradient and fouling angle, suitable bend geometric parameters are identified for avoiding the risk of fouling.

  8. Heat transfer when melting in the horizontal concentric annular gap and on finned tubes. Die Waermeuebertragung beim Schmelzen im horizontalen konzentrischen Ringspalt und am Rippenrohr

    Energy Technology Data Exchange (ETDEWEB)

    Betzel, T.

    1986-01-01

    Heat transfer in melting processes has aroused a great deal of interest recently because of the possibilities of using latent heat stores. Starting from explanations of the areas of use for latent heat stores, the possible storage media and types of store construction for active heating systems, there is an introductory phenomenological description of the melting process on resting and moving bodies and a survey of the literature. The melting and solidification processes due to purely thermal conduction (on plane walls, on cylindrical surfaces, in the concentric annular gap) and the differential equations decisive for the convection melting process are then explained. The melting process in the concentric annular gap with a falling solid body and the melting process around a horizontal tube with and without axial fins were also examined (density of heat flow, rate of melting, superimposition of boundary layer, phase boundaries). (HWJ).

  9. Flows and torques in Brownian ferrofluids subjected to rotating uniform magnetic fields in a cylindrical and annular geometry

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Diaz, I.; Cortes, A.; Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [Department of Chemical Engineering, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9000 (United States); Cedeño-Mattei, Y. [Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019 (United States); Perales-Perez, O. [Department of Engineering Science and Materials, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9044 (United States)

    2014-01-15

    Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ∼10{sup −8} kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.

  10. Review:Liquid film dryout model for predicting critical heat flux in annular two-phase flow

    Institute of Scientific and Technical Information of China (English)

    Bo JIAO; Li-min QIU; Jun-liang LU; Zhi-hua GAN

    2009-01-01

    Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposi-tion and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed.

  11. Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.

    Energy Technology Data Exchange (ETDEWEB)

    Dechant, Lawrence [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Smith, Justin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by

  12. MUSIG model analysis of flow boiling of liquid nitrogen in vertical annular pipe Part 2:The prediction of local mean radial distribution of Sauter diameter and interfacial area concentration%竖直环形通道内液氮流动沸腾的MUSIG模型分析第二部分: 径向气泡直径和界面面积浓度的预测

    Institute of Scientific and Technical Information of China (English)

    邵雪锋; 李祥东; 汪荣顺

    2009-01-01

    由于考虑了气泡的破裂和聚合,同两流体模型相比,MUSIG模型(多尺寸组模型)能更准确地描述流场内气泡直径.采用MUSIG模型详细分析了不同壁面热流量,液体入口速度,过冷度以及不同管道高度时通道内气泡相界面面积、当地气泡直径、空泡系数等参数沿径向的分布.分析结果表明,MUSIG模型可用来预测泡弹状流型转变区的流动参数,也即该模型拓展了两流体模型的使用范围.%Considering the mechanisms of bubble coalescence and breakage, MUSIG (Multiple-Size-Group) model can supply a more accurate description of the diameter of bubble in the boiling flow of liquid nitrogen comparing with two fluid model. The MUSIG model is applied here to analyze flow boiling of liquid nitrogen in a vertical annular channel, local radial distribution of the mean interfacial area concentration, Sauter diameter and void fraction with different liquid inlet velocity, heat flux , liquid inlet subcooling and height of tube in vertical annular pipe. The numerical results illustrates that the MUSIG model can be used to predict flow parameters in the two phase flow structures from bubbly to slug or churn turbulent boiling flows., which also mean the use of two fluid flow is extended by the MUSIG model.

  13. An empirical investigation on Cu/Ethylene Glycol nanofluid through a concentric annular tube and proposing a correlation for predicting Nusselt number

    Directory of Open Access Journals (Sweden)

    A. Jafarimoghaddam

    2016-06-01

    Full Text Available The investigation indicates an experimental study on the convective heat transfer of Cu/Ethylene Glycol nanofluid flow inside a concentric annular tube with constant heat flux boundary condition and proposes a novel correlation for the prediction of Nusselt number. For extending the previous study by Jafarimoghaddam et al., we selected the nanoparticles with the average size of 20 nm and also other conditions of the experiment are based on Jafarimoghaddam et al. (2016 [1]. The applied nanofluid was prepared by Electrical Explosion of Wire technique with no accumulation during the experiment. The tube was heated using an electrical heating coil covered it. The effects of different parameters such as flow Reynolds number and nanofluid particle concentration on heat transfer coefficient are studied. The acquired experimental data were used to establish a correlation for predicting Nusselt number of nanofluid flow inside the annular tube. This correlation has been presented by using the exponential regression analysis and least square method. Correlation is valid for Cu/Base Ethylene Glycol nanofluid flow with the volume concentrations between 0.011 and 0.171 in the hydrodynamically fully developed laminar flow regime with Re < 160 which is most applicable in micro heat sinks.

  14. A two-dimensional parabolic model for vertical annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, F.M.; Toledo, A. Alvarez; Paladino, E.E. [Graduate Program in Mechanical Engineering, Universidade Federal de Rio Grande do Norte, Natal, RN (Brazil)], e-mail: emilio@ct.ufrn.br

    2010-07-01

    This work presents a solution algorithm for predicting hydrodynamic parameters for developing and equilibrium, adiabatic, annular, vertical two-phase flow. It solves mass and momentum transport differential equations for both the core and the liquid film across their entire domains. Thus, the velocity and shear stress distributions from the tube center to the wall are obtained, together with the average film thickness and the pressure gradient, making no use of empirical closure relations nor assuming any known velocity profile to solve the triangular relationship in the liquid film. The model was developed using the Finite Volume Method and an iterative procedure is proposed to solve all flow variables for given phase superficial velocities. The procedure is validated against the analytical solution for laminar flow and experimental data for gas-liquid turbulent flow with entrainment. For the last case, an algebraic turbulence model is used for turbulent viscosity calculation for both, liquid film and gas core. (author)

  15. Experimental Investigation of the Three—Dimensional Flow in an Annular Compressor Cascade at Large Incidence

    Institute of Scientific and Technical Information of China (English)

    TuhongLi; DajunYe; 等

    1992-01-01

    This paper presents a detalied experimental investigation concerning the influence of blade loading (incidence) on the three -dimensional flow in an annular compressor cascade.The data are acquired at four incidence angles under low Mach number and low Reynolds number conditions.ExPerimental techniques include the oil-film visualization on the profile and the endwall surfaces,the laser-sheet visualization of the flow field inside the blade passae,and the measurement by radial-circumferential traverses using a seven-hloe probe.The behavior and nature of the three-dimensional flow with severs separations inside the blade passage and at the exit are obtained.The distributions of the total pressure loss,static pressure.Velocity and outflow angle are also given.Theses results are valuable for establishing the physical model of the three-dimensional complex flow in axial compressor and for examinig the computational procedures.

  16. [Flow field test on the tangential section of polypropylene tubular membrane module annular gap in rotating linear tangential flow].

    Science.gov (United States)

    Wang, Chengduan; Chen, Wenmei; Li, Jianming; Jiang, Guangming

    2002-07-01

    A new type of polypropylene tubular membrane apparatus of rotating cross flow was designed to study experimentally the flow field characteristics of the tangential section of the membrane annular gap. The authors designed rotary linear tangential flow tubular membrane separator and its test system for the first time. Through the system, the flow field of rotary linear tangential flow with the advanced Particle Image Velocimetry (PIV) was tested for the first time. A lot of streamlines and vorticity maps of the tangential section of separator in different operation conditions were obtained. The velocity distribution characteristics were analyzed quantitatively: 1. At non-vortex area, no matter how the operation parameters change, the velocity near to rotary tangential flow entrance was higher than the velocity far from entrance at the same radial coordinates. At vortex area, generally the flow velocity of inner vortex was lower than the outer vortex. At the vortex center, the velocity was lowest, the tangential velocity were equal to zero generally. At the vortex center zone, the tangential velocity was less than the axial velocity. 2. Under test operations, the tangential velocity and axial velocity of vortices borders are 1-2 times of average axial velocity of membrane module annular gap. The maximum tangential velocity and axial velocity of ellipse vortices were 2-6 times of average axial velocity of membrane module annular gap. 3. The vortices that are formed on the tangential section, there existed mass transfer between inner and outer parts of fluid. Much fluid of outer vortices got into the inner ones, which was able to prevent membrane tube from particles blocking up very soon.

  17. Transmission of sound through annular ducts of varying cross sections and sheared mean flow

    Science.gov (United States)

    Nayfeh, A. H.; Kaiser, J. E.; Telionis, D. P.

    1974-01-01

    An asymptotic solution is presented for the transmission and attenuation of acoustic waves in an annular duct of slowly varying cross section which carries a sheared mean flow. The analysis also takes into account the growth of the boundary layer as well as any slow variations in the acoustic liner properties. The problem is reduced to the solution of a first-order ordinary differential equation for the amplitude. The analysis is used to estimate the effects of the variations of the duct cross section and boundary layer growth on the different acoustic modes.

  18. Study on Friction Factor of Developing and Developed Laminar FLow in Annular-Sector Ducts

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    The pressure drops of laminar developing and developed flow in annular-sector ducts with small roud corner have been investigated experimentally.Numerical simulation has been performed to study the effect of the small round corner on the friction factor in the developed region.It has been found that with the increase in corner radius,the value of f Re decreases,In the range of rc/ro from 0.031to 0.12,the decrease in fRe varies from 0.048%to 0.1% for the fie apex angle computed.

  19. On-line gaseous formaldehyde detection by a microfluidic analytical method based on simultaneous uptake and derivatization in a temperature controlled annular flow.

    Science.gov (United States)

    Guglielmino, Maud; Bernhardt, Pierre; Trocquet, Claire; Serra, Christophe A; Le Calvé, Stéphane

    2017-09-01

    This paper is focused on the improvement of a microfluidic analytical method for the detection of low airborne formaldehyde concentrations, based on only two distinct steps permitting to reduce the response time and to improve the compactness of the device. First, gaseous formaldehyde is trapped into an acetylacetone solution at 65°C through an annular liquid/gas flow and reacts immediately to form 3,5-Diacetyl-1,4-dihydrolutidine which is then quantified by colorimetry using a liquid core waveguide (LCW). To obtain an annular flow, 3 different hydrophilic silica capillaries of 320, 450 and 530µm ID were tested and the corresponding phase diagrams were obtained in the ranges of liquid and gas flows of 5-35µLmin(-1) and 5-35mLmin(-1) respectively. Finally, the analytical performances were determined using the lowest flow values of 5µLmin(-1) and 5NmLmin(-1), ensuring an annular flow and increasing the microdevice autonomy. If the uptake yield of gaseous formaldehyde into the solution was close to 100%, only the 530µm ID capillary permits to obtain a reaction time long enough for a full conversion of formaldehyde into 3,5-Diacetyl-1,4-dihydrolutidine. With a LCW pathlength of 5cm, the microdevice response was perfectly linear in the range 0-154µgm(-3) with a detection limit of 1.8µgm(-3). Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Linear stability analysis of axisymmetric flow over a sudden expansion in an annular pipe

    Science.gov (United States)

    Beladi, Behnaz; Kuhlmann, Hendrik Christoph

    2016-11-01

    A global temporal linear stability analysis is performed of the fully-developed axisymmetric incompressible Newtonian flow in an annular pipe with a sudden radially-inward expansion. The geometry is characterized by the radial expansion ratio (radial step height to the outlet gap width) and the outlet radius ratio (inner-to-outer radius). Stability boundaries have been calculated with finite volumes for an outlet radius ratio of 0 . 1 and expansion ratios from 0 . 25 to 0 . 75 . For expansion ratios less than 0 . 55 the most dangerous mode has an azimuthal wave number m = 3 , whereas m = 2 for larger expansion ratios. An a posteriori analysis of the kinetic energy transferred between the basic state and the critical mode allows to check the energy conservation and to identify the physical instability mechanism. For all expansion ratios considered the basic flow arises as an annular jet between two separation zones which are located immediately after the step. The jet gradually widens downstream before reattaching to the cylinders. The deceleration of the flow associated with the widening of the jet is found to be the primary source of energy for the critical modes.

  1. Correlation and spectral measurements of fluctuating pressures and velocities in annular turbulent flow. [PWR; BWR

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, R.J.; Jones, B.G.; Roy, R.P.

    1980-02-01

    An experimental study of the fluctuating velocity field, the fluctuating static wall pressure and the in-stream fluctuating static pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field; fluctuating static wall pressure and in-stream fluctuating static pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, the cross-correlation between the fluctuating static wall pressure and the fluctuating static pressure in the core region of the flow and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained.

  2. Operation control of fluids pumping in curved pipes during annular flow: a numerical evaluation

    Directory of Open Access Journals (Sweden)

    T Andrade

    2016-10-01

    Full Text Available To generate projects which provide significant volume recovery from heavy oils reservoirs and improve existing projects, is important to develop new production and transport technologies, especially in the scenario of offshore fields. The core-flow technique is one of new technologies used in heavy oil transportation. This core-flow pattern is characterized by a water pellicle that is formed close or adjacent to the inner wall of the pipe, functioning as a lubricant. The oil flows in the center of the pipe causing a reduction in longitudinal pressure drop. In this sense, this work presents a numerical study of heavy oil annular flow (core-flow assisted by computational tool ANSYS CFX® Release 12.0. It was used a three-dimensional, transient and isothermal mathematical model considered by the mixture and turbulence - models to address the water-heavy oil two-phase flow, assuming laminar flow for oil phase and turbulent flow for water phase. Results of the pressure, velocity and volume fraction distributions of the phases and the pressure drop for different operation conditions are presented and evaluated. It was observed that the oil core flowing eccentrically in the pipe and stops of the water flux considerably increases the pressure drop in the pipe after the restart of the pump.

  3. A study on the counter current and cocurrent annular flow critical heat flux under low flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Park, Cheol

    1998-02-15

    Empirical and phenomenological investigations have been performed for countercurrent and cocurrent annular flow critical heat fluxes(CHFs) under low flow conditions. The CHF characteristics on finned surfaces were also examined by experiments and analyses for finned and unfinned geometries. A new form of C{sub w}{sup 2} in the Wallis flooding correlation was proposed for a general use in predicting the flooding limited CHF at tubes, annuli and rectangular channels under zero and very low flow conditions. The suggested correlation showed reasonable predictions compared to the measured CHF with an root-mean-square(RMS) error of 18.8%. A physical model for the prediction of a CHF location at a zero inlet flow condition was improved to take into account entrainment from the liquid film and to extend the applicable range to subcooled inlet flow conditions. The improved model showed reasonable agreements with the Katto data, and provided details of the CHF mechanism due to flooding. It was analytically confirmed that the flooding is a triggering mechanism of a countercurrent annular flow CHF under zero and very low flow conditions. It was also revealed that the heat flux effect such as the nucleation induced entrainment in the liquid film should be considered for the analysis of a flooding limited CHF, especially in small L/D geometry. In addition, an attempt was made to predict CHF values by applying the improved model with predetermined CHF locations. The results showed that the predictions by the improved physical model agreed reasonably with the experimental data. Annular flow hydrodynamic models of Whalley, Levy and Katto, which were developed for high flow conditions, were compared with available low flow CHF data to make out the applicability of the models to low flow conditions. As a result, it was found that Katto model, which improved the fault of Whally and Levy models, could be applied to predict low flow CHF with some improvements although the model

  4. Algebraically explicit analytical solutions for the unsteady non-Newtonian swirling flow in an annular pipe

    Institute of Scientific and Technical Information of China (English)

    CAI; Ruixian; GOU; Chenhua

    2006-01-01

    This paper presents two algebraically explicit analytical solutions for the incompressible unsteady rotational flow of Oldroyd-B type in an annular pipe. The first solution is derived with the common method of separation of variables. The second one is deduced with the method of separation of variables with addition developed in recent years. The first analytical solution is of clear physical meaning and both of them are fairly simple and valuable for the newly developing computational fluid dynamics. They can be used as the benchmark solutions to verify the applicability of the existing numerical computational methods and to inspire new differencing schemes, grid generation ways, etc. Moreover, a steady solution for the generalized second grade rheologic fluid flow is also presented. The correctness of these solutions can be easily proven by substituting them into the original governing equation.

  5. Characterization of interfacial waves and pressure drop in horizontal oil-water core-annular flows

    Science.gov (United States)

    Tripathi, Sumit; Tabor, Rico F.; Singh, Ramesh; Bhattacharya, Amitabh

    2017-08-01

    We study the transportation of highly viscous furnace-oil in a horizontal pipe as core-annular flow (CAF) using experiments. Pressure drop and high-speed images of the fully developed CAF are recorded for a wide range of flow rate combinations. The height profiles (with respect to the centerline of the pipe) of the upper and lower interfaces of the core are obtained using a high-speed camera and image analysis. Time series of the interface height are used to calculate the average holdup of the oil phase, speed of the interface, and the power spectra of the interface profile. We find that the ratio of the effective velocity of the annular fluid to the core velocity, α , shows a large scatter. Using the average value of this ratio (α =0.74 ) yields a good estimate of the measured holdup for the whole range of flow rate ratios, mainly due to the low sensitivity of the holdup ratio to the velocity ratio. Dimensional analysis implies that, if the thickness of the annular fluid is much smaller than the pipe radius, then, for the given range of parameters in our experiments, the non-dimensional interface shape, as well as the non-dimensional wall shear stress, can depend only on the shear Reynolds number and the velocity ratio. Our experimental data show that, for both lower and upper interfaces, the normalized power spectrum of the interface height has a strong dependence on the shear Reynolds number. Specifically, for low shear Reynolds numbers, interfacial modes with large wavelengths dominate, while, for large shear Reynolds numbers, interfacial modes with small wavelengths dominate. Normalized variance of the interface height is higher at lower shear Reynolds numbers and tends to a constant with increasing shear Reynolds number. Surprisingly, our experimental data also show that the effective wall shear stress is, to a large extent, proportional to the square of the core velocity. Using the implied scalings for the holdup ratio and wall shear stress, we can derive

  6. Heat transfer coefficient for flow boiling in an annular mini gap

    Directory of Open Access Journals (Sweden)

    Hożejowska Sylwia

    2016-01-01

    Full Text Available The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface – fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two–phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.

  7. Heat transfer coefficient for flow boiling in an annular mini gap

    Science.gov (United States)

    Hożejowska, Sylwia; Musiał, Tomasz; Piasecka, Magdalena

    2016-03-01

    The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface - fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two-phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.

  8. Electrical Capacitance Probe Characterization in Vertical Annular Two-Phase Flow

    Directory of Open Access Journals (Sweden)

    Grazia Monni

    2013-01-01

    Full Text Available The paper presents the experimental analysis and the characterization of an electrical capacitance probe (ECP that has been developed at the SIET Italian Company, for the measurement of two-phase flow parameters during the experimental simulation of nuclear accidents, as LOCA. The ECP is used to investigate a vertical air/water flow, characterized by void fraction higher than 95%, with mass flow rates ranging from 0.094 to 0.15 kg/s for air and from 0.002 to 0.021 kg/s for water, corresponding to an annular flow pattern. From the ECP signals, the electrode shape functions (i.e., the signals as a function of electrode distances in single- and two-phase flows are obtained. The dependence of the signal on the void fraction is derived and the liquid film thickness and the phase’s velocity are evaluated by means of rather simple models. The experimental analysis allows one to characterize the ECP, showing the advantages and the drawbacks of this technique for the two-phase flow characterization at high void fraction.

  9. Exact solutions for the flow of non-Newtonian fluid with fractional derivative in an annular pipe

    Science.gov (United States)

    Tong, Dengke; Wang, Ruihe; Yang, Heshan

    2005-08-01

    This paper deals with some unsteady unidirectional transient flows of Oldroyd-B fluid in an annular pipe. The fractional calculus approach in the constitutive relationship model Oldroyd-B fluid is introduced and a generalized Jeffreys model with the fractional calculus has been built. Exact solutions of some unsteady flows of Oldroyd-B fluid in an annular pipe are obtained by using Hankel transform and Laplace transform for fractional calculus. The following four problems have been studied: (1) Poiseuille flow due to a constant pressure gradient; (2) axial Couette flow in an annulus; (3) axial Couette flow in an annulus due to a longitudinal constant shear; (4) Poiseuille flow due to a constant pressure gradient and a longitudinal constant shear. The well-known solutions for Navier-Stokes fluid, as well as those corresponding to a Maxwell fluid and a second grade one, appear as limited cases of our solutions.

  10. Exact solutions for the flow of non-Newtonian fluid with fractional derivative in an annular pipe

    Institute of Scientific and Technical Information of China (English)

    TONG Dengke; WANG Ruihe; YANG Heshan

    2005-01-01

    This paper deals with some unsteady unidirectional transient flows of Oldroyd-B fluid in an annular pipe. The fractional calculus approach in the constitutive relationship model Oldroyd-B fluid is introduced and a generalized Jeffreys model with the fractional calculus has been built. Exact solutions of some unsteady flows of Oldroyd-B fluid in an annular pipe are obtained by using Hankel transform and Laplace transform for fractional calculus. The following four problems have been studied: (1) Poiseuille flow due to a constant pressure gradient; (2) axial Couette flow in an annulus; (3) axial Couette flow in an annulus due to a longitudinal constant shear; (4) Poiseuille flow due to a constant pressure gradient and a longitudinal constant shear. The well-known solutions for Navier-Stokes fluid, as well as those corresponding to a Maxwell fluid and a second grade one, appear as limited cases of our solutions.

  11. Three-dimensional direct numerical simulations of co/counter-current vertical gas-Liquid annular flows

    Science.gov (United States)

    Farhaoui, Asma; Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard; Matar, Omar

    2016-11-01

    We carry out three-dimensional numerical simulations of co/counter current Gas-Liquid annular flows using the parallel code, BLUE, based on a projection method for the resolution of the Navier-Stokes equations and a hybrid Front-Tracking/Level-Set method for the interface advection. Gas-Liquid annular flows and falling films in a pipe are present in a broad range of industrial processes. This configuration consists of an important multiphase flow regime where the liquid occupies the area adjacent to the internal circumference of the pipe and the gas flows in the pipe core. Experimentally, four distinctive flow regimes were identified ('dual-wave', 'thick ripple', 'disturbance wave' and 'regular wave' regimes), that we attempt to simulate. In order to visualize these different regimes, various liquid (water) and gas (air) flow-rates are investigated. EPSRC UK Programme Grant EP/K003976/1.

  12. Study of downward annular pipe flow using combined laser-based approaches

    Science.gov (United States)

    An, Jae Sik; Cherdantsev, Andrey; Zadrazil, Ivan; Matar, Omar; Markides, Christos

    2016-11-01

    In downward annular flow, the liquid phase flows as a film along the pipe wall and the gas flows in the core of the pipe. The liquid free-surface is covered by a complex multiscale system of waves. The interaction dynamics of the interfacial waves with each other and with the gas stream exert a significant influence on the pressure drop, heat transfer and mass interchange between the phases. The complexity of the interface requires the application of measurement techniques with high spatiotemporal resolution. In this work, two approaches based on the principle of laser-induced fluorescence, namely planar LIF and brightness-based LIF, are applied simultaneously to study interfacial phenomena in these flows, while simultaneous LIF and PIV are used to obtain velocity field information in the liquid phase underneath the waves. Sources of measurement bias are then analysed: total internal reflection at the out-of-plane interface; steep longitudinal slopes and transverse wave curvature; presence of gas bubbles in the liquid film. Although each method has its own limitations, a combined technique can provide reliable spatiotemporal measurements of film thickness to accompany the velocity information. Finally, flow development is studied in a moving frame of reference over long lengths. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).

  13. Unsteady fluid flow in a slightly curved annular pipe: The impact of the annulus on the flow physics

    Science.gov (United States)

    Messaris, Gerasimos A. T.; Karahalios, George T.

    2017-02-01

    The motivation of the present study is threefold. Mainly, the etiological explanation of the Womersley number based on physical reasoning. Next, the extension of a previous work [Messaris, Hadjinicolaou, and Karahalios, "Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution," Phys. Fluids 28, 081901 (2016)] to the annular pipe flow. Finally, the discussion of the effect of the additional stresses generated by a catheter in an artery and exerted on the arterial wall during an in vivo catheterization. As it is known, the square of the Womersley number may be interpreted as an oscillatory Reynolds number which equals to the ratio of the inertial to the viscous forces. The adoption of a modified Womersley number in terms of the annular gap width seems therefore more appropriate to the description of the annular flow than an ordinary Womersley number defined in terms of the pipe radius. On this ground, the non-dimensional equations of motion are approximately solved by two analytical methods: a matched asymptotic expansions method and a single. In the first method, which is valid for very large values of the Womersley number, the flow region consists of the main core and the two boundary layers formed at the inner and outer boundaries. In the second, the fluid is considered as one region and the Womersley number can vary from finite values, such that they fit to the blood flow in the aorta and the main arteries, to infinity. The single solution predicts increasing circumferential and decreasing axial stresses with increasing catheter radius at a prescribed value of the Womersley parameter in agreement with analogous results from other theoretical and numerical solutions. It also predicts the formation of pinches on the secondary flow streamlines and a third boundary layer, additional to those formed at the boundary walls. Finally, we show that the insertion of a catheter in an

  14. A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

    Science.gov (United States)

    Karimi, Amir

    1991-01-01

    NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

  15. Simulation of laminar and turbulent concentric pipe flows with the isogeometric variational multiscale method

    KAUST Repository

    Ghaffari Motlagh, Yousef

    2013-01-01

    We present an application of the residual-based variational multiscale modeling methodology to the computation of laminar and turbulent concentric annular pipe flows. Isogeometric analysis is utilized for higher-order approximation of the solution using Non-Uniform Rational B-Splines (NURBS). The ability of NURBS to exactly represent curved geometries makes NURBS-based isogeometric analysis attractive for the application to the flow through annular channels. We demonstrate the applicability of the methodology to both laminar and turbulent flow regimes. © 2012 Elsevier Ltd.

  16. Comparison of thermal and hydraulic performances of eccentric and concentric annular-fins of heat exchanger tubes

    Science.gov (United States)

    Benmachiche, Abdelmoumène Hakim; Tahrour, Farouk; Aissaoui, Faris; Aksas, Mounir; Bougriou, Cherif

    2017-08-01

    The present study is an experimental and 3-D computational fluid dynamics. It is used to compare between the heat transfer characteristics and pressure drops of eccentric and concentric annular-finned tube bundles. The RNG k-ɛ turbulence model of fluent is used to determine the optimum tube position in the circular fin that gives the highest thermal and hydraulic performances for both staggered and aligned arrangements. Then, experiments and numerical simulations were performed to examine the effects of bundle configurations, the Reynolds number (ranging from 5500 to 29,700) and the tube location inside the heat exchangers. A satisfactory qualitative and quantitative agreement was obtained between the numerical and experimental results. For both aligned and staggered heat exchangers, the thermal characteristics of the eccentric annular-finned tube are greater than that of the concentric ones. This gain is associated with reduction in pressure drop.

  17. Comparison of thermal and hydraulic performances of eccentric and concentric annular-fins of heat exchanger tubes

    Science.gov (United States)

    Benmachiche, Abdelmoumène Hakim; Tahrour, Farouk; Aissaoui, Faris; Aksas, Mounir; Bougriou, Cherif

    2017-02-01

    The present study is an experimental and 3-D computational fluid dynamics. It is used to compare between the heat transfer characteristics and pressure drops of eccentric and concentric annular-finned tube bundles. The RNG k-ɛ turbulence model of fluent is used to determine the optimum tube position in the circular fin that gives the highest thermal and hydraulic performances for both staggered and aligned arrangements. Then, experiments and numerical simulations were performed to examine the effects of bundle configurations, the Reynolds number (ranging from 5500 to 29,700) and the tube location inside the heat exchangers. A satisfactory qualitative and quantitative agreement was obtained between the numerical and experimental results. For both aligned and staggered heat exchangers, the thermal characteristics of the eccentric annular-finned tube are greater than that of the concentric ones. This gain is associated with reduction in pressure drop.

  18. Wall pressure measurements of flooding in vertical countercurrent annular air–water flow

    Energy Technology Data Exchange (ETDEWEB)

    Choutapalli, I., Vierow, K.

    2010-01-01

    An experimental study of flooding in countercurrent air-water annular flow in a large diameter vertical tube using wall pressure measurements is described in this paper. Axial pressure profiles along the length of the test section were measured up to and after flooding using fast response pressure transducers for three representative liquid flow rates representing a wide range of liquid Reynolds numbers (ReL = 4Γ/μ; Γ is the liquid mass flow rate per unit perimeter; μ is the dynamic viscosity) from 3341 to 19,048. The results show that flooding in large diameter tubes cannot be initiated near the air outlet and is only initiated near the air inlet. Fourier analysis of the wall pressure measurements shows that up to the point of flooding, there is no dominant wave frequency but rather a band of frequencies encompassing both the low frequency and the broad band that are responsible for flooding. The data indicates that flooding in large diameter vertical tubes may be caused by the constructive superposition of a plurality of waves rather than the action of a single large-amplitude wave.

  19. Flow Stability Model for Fan/Compressors with Annular Duct and Novel Casing Treatment

    Institute of Scientific and Technical Information of China (English)

    LIU Xiaohua; SUN Dakun; SUN Xiaofeng; WANG Xiaoyu

    2012-01-01

    A three-dimensional compressible flow stability model is presented in this paper,which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time.It is shown that under some assumptions,the stability equation can be obtained yielding from a group of homogeneous equations.The stability can be judged by the non-dimensional imaginary part of the resultant complex frequency eigenvalue.Further more,based on the analysis of the unsteady phenomenon caused by casing treatment,the function of casing treatment has been modeled by a wall impedance condition which is included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system.Finally,some experimental investigation and two numerical evaluation cases are conducted to validate this model and emphasis is placed on numerically studying the sensitivity of the setup of different boundary conditions on the stall inception of axial flow fan/compressors.A novel casing treatment which consists ofa backchamber and a perforated plate is suggested,and it is noted that the open area ratio of the casing treatment is less than 10%,and is far smaller than conventional casing treatment with open area ratio of over 50%,which could result in stall margin improvement without obvious efficiency loss of fan/compressors.

  20. UNSTEADY HEAT TRANSFER IN AN ANNULAR PIPE. PART II: SWIRLING LAMINAR FLOW

    Directory of Open Access Journals (Sweden)

    Kelvin Ho Choon Seng

    2012-02-01

    Full Text Available The   heat  transfer   problem  in   magnetocaloric regenerators  during  magnetization  has  been  described  and investigated for convective heat transfer by means of axial flow in part I of this series.   This work will focus on enhancing the unsteady heat  transfer using swirling laminar flow generated using axial vanes.   The governing parameters for this  studyare,  the  D*  ratio  (Inner  diameter/Outer  diameter  and  the swirl number, S.   The study is conducted  using  dimensional analysis and commercial CFD codes provided by ANSYS CFX. The  hydrodynamics and the  heat transfer of the  model are compared with data from similar cases found in literature and is found to be in the vicinity of good agreement.Keywords-  Annular ducts; unsteady heat transfer;  magnetic refrigeration/cooling;   swirling   laminar    flow;    dimensional analysis.

  1. Electrically driven convection in a thin annular film undergoing Couette flow

    CERN Document Server

    Daya, Z A; Morris, S W; Daya, Zahir A.; Morris, Stephen W.

    1998-01-01

    We investigate the linear stability of a thin, suspended, annular film of conducting fluid with a voltage difference applied between its inner and outer edges. For a sufficiently large voltage, such a film is unstable to radially-driven electroconvection due to charges which develop on its free surfaces. The film can also be subjected to a Couette shear by rotating its inner edge. This combination is experimentally realized using films of smectic A liquid crystals. In the absence of shear, the convective flow consists of a stationary, azimuthally one-dimensional pattern of symmetric, counter-rotating vortex pairs. When Couette flow is applied, an azimuthally traveling pattern results. When viewed in a co-rotating frame, the traveling pattern consists of pairs of asymmetric vortices. We calculate the neutral stability boundary for arbitrary radius ratio $\\alpha$ and Reynolds number ${R e}$ of the shear flow, and obtain the critical control parameter $R_c (\\alpha, {R e})$ and the critical azimuthal mode number ...

  2. A PCM/forced convection conjugate transient analysis of energy storage systems with annular and countercurrent flows

    Science.gov (United States)

    Cao, Y.; Faghri, A.; Juhasz, A.

    1991-01-01

    Latent heat energy storage systems with both annular and countercurrent flows are modeled numerically. The change of phase of the phase-change material (PCM) and the transient forced convective heat transfer for the transfer fluid are solved simultaneously as a conjugate problem. A parametric study and a system optimization are conducted. It is found that the energy storage system with the countercurrent flow is an efficient way to absorb heat energy in a short period for pulsed power load space applications.

  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

    2017-07-01

    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. Linear stability of a surfactant-laden annular film in a time-periodic pressure-driven flow through a capillary.

    Science.gov (United States)

    Wei, Hsien-Hung; Halpern, David; Grotberg, James B

    2005-05-15

    This paper analyzes the effect of surfactant on the linear stability of an annular film in a capillary undergoing a time-periodic pressure gradient force. The annular film is thin compared to the radius of the tube. An asymptotic analysis yields a coupled set of equations with time-periodic coefficients for the perturbed fluid-fluid interface and the interfacial surfactant concentration. Wei and Rumschitzki (submitted for publication) previously showed that the interaction between a surfactant and a steady base flow could induce a more severe instability than a stationary base state. The present work demonstrates that time-periodic base flows can modify the features of the steady-flow-based instability, depending on surface tension, surfactant activity, and oscillatory frequency. For an oscillatory base flow (with zero mean), the growth rate decreases monotonically as the frequency increases. In the low-frequency limit, the growth rate approaches a maximum corresponding to the growth rate of a steady base flow having the same amplitude. In the high-frequency limit, the growth rate reaches a minimum corresponding to the growth rate in the limit of a stationary base state. The underlying mechanisms are explained in detail, and extension to other time-periodic forms is further exploited.

  5. Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

    Science.gov (United States)

    Boltenko, E. A.

    2016-10-01

    The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

  6. Transient mathematical model for the axial annular fluid flow caused by drillpipe motion

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Hudson F.; Ramalho, Vanessa A.O.; Negrao, Cezar O.R.; Junqueira, Silvio L.M. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Dept. Academico de Mecanica. Lab. de Ciencias Termicas]. E-mails: hudsonhfk@yahoo.com.br; vanessinha123@gmail.com; negrao@utfpr.edu.br; silvio@utfpr.edu.br; Martins, Andre Leibsohn [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Tecnologia de Engenharia de Pocos (TEP)]. E-mail: aleibsohn@petrobras.com.br

    2008-07-01

    The axial movement of drill pipes is a common operation in oil well drilling. This motion displaces the drilling fluid and causes pressure changes in the borehole. The descending pipe movement increases the pressure at the bottomhole (surge) and its extraction reduces it (swab). If the bottomhole pressure overcomes the formation fracture pressure, circulation loss may take place. On the other hand, if the pressure within the well is smaller than the pore pressure, kicks can occur. In order to maintain the bottomhole pressure within the formation fracture and pore pressures, the drill pipe must be moved slowly and therefore, the task becomes quite time consuming. The current work presents a mathematical model to predict surge and swab pressures in annular spaces. The approach is based on conservation equations of mass and momentum. The fluid flow is considered laminar, one-dimensional, compressible, isothermal and transient. The fluid is regarded as Newtonian with constant compressibility. The viscous effect is lumped and the concept of friction factor is applied. The governing differential equations are non-linear and therefore, they are solved numerically by the finite volume method. A sensitivity analysis of the flow parameters is carried out. For instance, the pressure wave propagation is observed for low compressibility fluids. Pressure oscillation is observed for low aspect ratio ratios. (author)

  7. Simulations and measurements of adiabatic annular flows in triangular, tight lattice nuclear fuel bundle model

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Abhishek, E-mail: asaxena@lke.mavt.ethz.ch [ETH Zurich, Laboratory for Nuclear Energy Systems, Department of Mechanical and Process Engineering, Sonneggstrasse 3, 8092 Zürich (Switzerland); Zboray, Robert [Laboratory for Thermal-hydraulics, Nuclear Energy and Safety Department, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Prasser, Horst-Michael [ETH Zurich, Laboratory for Nuclear Energy Systems, Department of Mechanical and Process Engineering, Sonneggstrasse 3, 8092 Zürich (Switzerland); Laboratory for Thermal-hydraulics, Nuclear Energy and Safety Department, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)

    2016-04-01

    High conversion light water reactors (HCLWR) having triangular, tight-lattice fuels bundles could enable improved fuel utilization compared to present day LWRs. However, the efficient cooling of a tight lattice bundle has to be still proven. Major concern is the avoidance of high-quality boiling crisis (film dry-out) by the use of efficient functional spacers. For this reason, we have carried out experiments on adiabatic, air-water annular two-phase flows in a tight-lattice, triangular fuel bundle model using generic spacers. A high-spatial-resolution, non-intrusive measurement technology, cold neutron tomography, has been utilized to resolve the distribution of the liquid film thickness on the virtual fuel pin surfaces. Unsteady CFD simulations have also been performed to replicate and compare with the experiments using the commercial code STAR-CCM+. Large eddies have been resolved on the grid level to capture the dominant unsteady flow features expected to drive the liquid film thickness distribution downstream of a spacer while the subgrid scales have been modeled using the Wall Adapting Local Eddy (WALE) subgrid model. A Volume of Fluid (VOF) method, which directly tracks the interface and does away with closure relationship models for interfacial exchange terms, has also been employed. The present paper shows first comparison of the measurement with the simulation results.

  8. Investigation of the Left Ventricular Flow Dynamics in the Presence of Severe Mitral Annular Calcification

    Science.gov (United States)

    El-Sayegh, Batoul; Kadem, Lyes; di Labbio, Giuseppe; Pressman, Gregg S.; Obasare, Edinrin

    2016-11-01

    Valvular calcification is frequent with aging and diverse diseases. Mitral annular calcification (MAC) is a degenerative process where the fibrous annulus of the mitral valve degrades. MAC can be found in approximately 40% of people aged over 65. It is associated with increased occurrence of cardiovascular diseases including stroke. This experimental work is aimed to investigate the effects of MAC on the left ventricle (LV) hemodynamics and to develop new clinical parameters. Two patient-specific 3D-printed mitral valves with moderate and severe MACs were placed in a left heart simulator. The velocity fields in the LV were acquired using time-resolved particle image velocimetry (TR-PIV) and compared to normal LV flow. The velocity fields were used to evaluate the temporal evolution of the vorticity fields and viscous energy loss in the LV. The presence of MAC disturbed the flow in the LV leading to markedly increased viscous energy losses. As the severity of MAC increased, the velocity of the inflow jet also increased causing significant perturbations to the normally-occurring vortex in the LV.

  9. Analysis of flow boiling heat transfer in narrow annular gaps applying the design of experiments method

    Directory of Open Access Journals (Sweden)

    Gunar Boye

    2015-06-01

    Full Text Available The axial heat transfer coefficient during flow boiling of n-hexane was measured using infrared thermography to determine the axial wall temperature in three geometrically similar annular gaps with different widths (s = 1.5 mm, s = 1 mm, s = 0.5 mm. During the design and evaluation process, the methods of statistical experimental design were applied. The following factors/parameters were varied: the heat flux q · = 30 − 190 kW / m 2 , the mass flux m · = 30 − 700 kg / m 2 s , the vapor quality x · = 0 . 2 − 0 . 7 , and the subcooled inlet temperature T U = 20 − 60 K . The test sections with gap widths of s = 1.5 mm and s = 1 mm had very similar heat transfer characteristics. The heat transfer coefficient increases significantly in the range of subcooled boiling, and after reaching a maximum at the transition to the saturated flow boiling, it drops almost monotonically with increasing vapor quality. With a gap width of 0.5 mm, however, the heat transfer coefficient in the range of saturated flow boiling first has a downward trend and then increases at higher vapor qualities. For each test section, two correlations between the heat transfer coefficient and the operating parameters have been created. The comparison also shows a clear trend of an increasing heat transfer coefficient with increasing heat flux for test sections s = 1.5 mm and s = 1.0 mm, but with increasing vapor quality, this trend is reversed for test section 0.5 mm.

  10. A photosynthetic rotating annular bioreactor (Taylor-Couette type flow) for phototrophic biofilm cultures.

    Science.gov (United States)

    Paule, A; Lauga, B; Ten-Hage, L; Morchain, J; Duran, R; Paul, E; Rols, J L

    2011-11-15

    In their natural environment, the structure and functioning of microbial communities from river phototrophic biofilms are driven by biotic and abiotic factors. An understanding of the mechanisms that mediate the community structure, its dynamics and the biological succession processes during phototrophic biofilm development can be gained using laboratory-scale systems operating with controlled parameters. For this purpose, we present the design and description of a new prototype of a rotating annular bioreactor (RAB) (Taylor-Couette type flow, liquid working volume of 5.04 L) specifically adapted for the cultivation and investigation of phototrophic biofilms. The innovation lies in the presence of a modular source of light inside of the system, with the biofilm colonization and development taking place on the stationary outer cylinder (onto 32 removable polyethylene plates). The biofilm cultures were investigated under controlled turbulent flowing conditions and nutrients were provided using a synthetic medium (tap water supplemented with nitrate, phosphate and silica) to favour the biofilm growth. The hydrodynamic features of the water flow were characterized using a tracer method, showing behaviour corresponding to a completely mixed reactor. Shear stress forces on the surface of plates were also quantified by computer simulations and correlated with the rotational speed of the inner cylinder. Two phototrophic biofilm development experiments were performed for periods of 6.7 and 7 weeks with different inoculation procedures and illumination intensities. For both experiments, biofilm biomasses exhibited linear growth kinetics and produced 4.2 and 2.4 mg cm(-)² of ash-free dry matter. Algal and bacterial community structures were assessed by microscopy and T-RFLP, respectively, and the two experiments were different but revealed similar temporal dynamics. Our study confirmed the performance and multipurpose nature of such an innovative photosynthetic bioreactor

  11. Numerical analysis of flow instability in the water wall of a supercritical CFB boiler with annular furnace

    Science.gov (United States)

    Xie, Beibei; Yang, Dong; Xie, Haiyan; Nie, Xin; Liu, Wanyu

    2016-08-01

    In order to expand the study on flow instability of supercritical circulating fluidized bed (CFB) boiler, a new numerical computational model considering the heat storage of the tube wall metal was presented in this paper. The lumped parameter method was proposed for wall temperature calculation and the single channel model was adopted for the analysis of flow instability. Based on the time-domain method, a new numerical computational program suitable for the analysis of flow instability in the water wall of supercritical CFB boiler with annular furnace was established. To verify the code, calculation results were respectively compared with data of commercial software. According to the comparisons, the new code was proved to be reasonable and accurate for practical engineering application in analysis of flow instability. Based on the new program, the flow instability of supercritical CFB boiler with annular furnace was simulated by time-domain method. When 1.2 times heat load disturbance was applied on the loop, results showed that the inlet flow rate, outlet flow rate and wall temperature fluctuated with time eventually remained at constant values, suggesting that the hydrodynamic flow was stable. The results also showed that in the case of considering the heat storage, the flow in the water wall is easier to return to stable state than without considering heat storage.

  12. Visualization of the boiling phenomena and counter-current flow limit of annular heat pipe

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)

    2015-10-15

    The thermal resistance of conventional heat pipes increases over the capillary limit because of the insufficient supplement of the working fluid. Due to the shortage of the liquid supplement, thermosyphon is widely used for vertically oriented heat transport and high heat load conditions. Thermosyphons are two-phase heat transfer devices that have the highly efficient heat transport from evaporation to condensation section that makes an upward driving force for vapor. In the condenser section, the vapor condenses and releases the latent heat. Due to the gravitation force acting on the liquid in the tube, working fluid back to the evaporator section, normally this process operate at the vertical and inclination position. The use of two-phase closed thermosyphon (TPCT) for the cooling devices has the limitation due to the phase change of the working fluid assisted by gravity force. Due to the complex phenomenon of two-phase flow, it is required to understand what happened in TPCT. The visualization of the thermosyphon and heat pipe is investigated for the decrease of thermal resistance and enhancement of operation limit. Weibel et al. investigated capillary-fed boiling of water with porous sintered powder wick structure using high speed camera. At the high heat flux condition, dry-out phenomenon and a thin liquid film are observed at the porous wick structure. Wong and Kao investigated the evaporation and boiling process of mesh wicked heat pipe using optical camera. At the high heat flux condition, the water filing became thin and partial dry-out was observed in the evaporator section. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. The hybrid heat pipe is the combination of the heat pipe and control rod. It is necessary for PINCs to contain a neutron absorber (B{sub 4}C) to have the ability of reactivity control. It has annular vapor space and

  13. The method of characteristics and computational fluid dynamics applied to the prediction of underexpanded jet flows in annular geometry

    Science.gov (United States)

    Kim, Sangwon

    2005-11-01

    High pressure (3.4 MPa) injection from a shroud valve can improve natural gas engine efficiency by enhancing fuel-air mixing. Since the fuel jet issuing from the shroud valve has a nearly annular jet flow configuration, it is necessary to analyze the annular jet flow to understand the fuel jet behavior in the mixing process and to improve the shroud design for better mixing. The method of characteristics (MOC) was used as the primary modeling algorithm in this work and Computational Fluid Dynamics (CFD) was used primarily to validate the MOC results. A consistent process for dealing with the coalescence of compression characteristic lines into a shock wave during the MOC computation was developed. By the application of shock polar in the pressure-flow angle plane to the incident shock wave for an axisymmetric underexpanded jet and the comparison with the triple point location found in experimental results, it was found that, in the static pressure ratios of 2--50, a triple point of the jet was located at the point where the flow angle after the incident shock became -5° relative to the axis and this point was situated between the von Neumann and detachment criteria on the incident shock. MOC computations of the jet flow with annular geometry were performed for pressure ratios of 10 and 20 with rannulus = 10--50 units, Deltar = 2 units. In this pressure ratio range, the MOC results did not predict a Mach disc in the core flow of the annular jet, but did indicate the formation of a Mach disc where the jet meets the axis of symmetry. The MOC results display the annular jet configurations clearly. Three types of nozzles for application to gas injectors (convergent-divergent nozzle, conical nozzle, and aerospike nozzle) were designed using the MOC and evaluated in on- and off-design conditions using CFD. The average axial momentum per unit mass was improved by 17 to 24% and the average kinetic energy per unit fuel mass was improved by 30 to 80% compared with a standard

  14. CFD Method for Predicting Annular Pressure Losses and Cuttings Concentration in Eccentric Horizontal Wells

    Directory of Open Access Journals (Sweden)

    Titus N. Ofei

    2014-01-01

    Full Text Available In oil and gas drilling operations, predictions of pressure losses and cuttings concentration in the annulus are very complex due to the combination of interacting drilling parameters. Past studies have proposed many empirical correlations to estimate pressure losses and cuttings concentration. However, these developed correlations are limited to their experimental data range and setup, and hence, they cannot be applicable to all cases. CFD methods have the advantages of handling complex multiphase flow problems, as well as, an unlimited number of physical and operational conditions. The present study employs the inhomogeneous (Eulerian-Eulerian model to simulate a two-phase solid-fluid flow and predict pressure losses and cuttings concentration in eccentric horizontal annuli as a function of varying drilling parameters: fluid velocity, diameter ratio (ratio of inner pipe diameter to outer pipe diameter, inner pipe rotation speed, and fluid type. Experimental data for pressure losses and cuttings concentration from previous literature compared very well with simulation data, confirming the validity of the current model. The study shows how reliable CFD methods can replicate the actual, yet complex oil and gas drilling operations.

  15. Numerical Investigation on the Influence of Nozzle Lip Thickness on the Flow Field and Performance of an Annular Jet Pump

    Institute of Scientific and Technical Information of China (English)

    LongZhou Xiao; XinPing Long; XueLong Yang

    2014-01-01

    The performance of an annular jet pump ( AJP ) is determined by its area ratio A ( ratio of cross sectional area of throat and annular nozzle) and flow rate ratio q ( ratio of primary and secondary flow rate, Qs/Qj ) , while the nozzle lip thickness is neglected in the present studies. This paper presents a study on the effect of the thickness on the flow field and performance of an AJP with A = 1�75. With the increasing flow rate ratio and nozzle lip thickness, a small vortex forms at the nozzle lip and keeps on growing. However, as the flow rate ratio or nozzle lip thickness is extremely low, the vortex at the lip vanishes thoroughly. Moreover, the recirculation width varies conversely with the nozzle lip thickness when the flow rate ratio q≤0�13. While the deviation of the recirculation width with different nozzle lip thickness is negligible with q≥0�13. Additionally the existence of nozzle lip hinders the momentum exchange between the primary and secondary flow and leads to a mutation of velocity gradient near the nozzle exit, which shift the recirculation downstream. Finally, based on the numerical results of the streamwise and spanwise vortex distributions in the suction chamber, the characteristics of the mixing process and the main factors accounting for the AJP performance are clarified.

  16. Flow characteristics of annular flow at a micro-T-junction%T 形微通道内环状气液两相流相分离

    Institute of Scientific and Technical Information of China (English)

    周云龙; 刘博; 孙科

    2013-01-01

      Using air as gas working fluid and with liquids of different surface tensions (pure water, 0.01% SDS solution,0.5% SDS solution,ethanol) as working fluids,a visualization experiment was conducted to study the split of annular flow through a T-junction with a rectangular cross section (100μm×800 μm). The results showed that the liquid preferentially enters the side branch. Liquid taken off mainly concentrated in 0.25—0.65 and gas taken off mainly concentrated in 0.1—0.8. The rate of increase of liquid taken off become bigger with increase of gas taken off. It was found that the liquid taken off of annular flow decreases with an increase of superficial liquid velocity at a certain superficial gas velocity. When the superficial liquid velocity is certain,there is very little effect of inlet gas flow rate on the liquid taken off. We also found that the decrease in liquid surface tension make the liquid taken off increase. When the present data were compared to those from other diameter junctions,it is seen that the phase split characteristics of the annular flow is very dependent on pipe size.%  以氮气为气相工作介质,以不同表面张力的液体(纯水、0.01%SDS 溶液、0.5%SDS 溶液、乙醇)为液相工作介质,对矩形截面为100μm×800μm 的 T 形微通道内的气液环状流进行了相分离可视化实验。实验结果表明:环状流液相在侧支管中采出占优势。液相采出分率主要集中在0.25~0.65之间;气相采出分率在0.1~0.8,液相采出分率的增长幅度随着气相采出分率增加而变大。当气相表观速度一定时,液相采出分率随着两相流液体速度的增加而降低;当液体表观速度一定时,气体速度变化对液相采出分率影响不大;当两相的表观速度一定时,液相采出分率随着液体的表面张力降低而减小。所得实验数据与其它尺寸的数据进行比较,发现管径尺寸对环状流相分离有较大影响。

  17. Stability of core-annular flow of power-law fluids in the presence of interfacial surfactant

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The shear-thinning influence on the core-annular flow stability of two immiscible power-law fluids is considered by making a linear stability analysis.The flow is driven by an axial pressure gradient in a straight pipe with the interface between the two fluids occupied by an insoluble surfactant.Given the basic flow for this core-annular arrangement,the analytical solution is obtained with respect to the power-law fluid model.The linearized equations for the evolution of infinitesimal disturbances are derived and the stability problem is formulated as a generalized matrix eigenvalue problem,which is solved by using the software package Matlab based on the QZ algorithm.The shear-thinning property is found to have marked influence on the power-law fluid core-annular flow stability,which is reflected in various aspects.First,the capillary instability is magnified by the shear-thinning property,which may lead to an essential difference between power-law and Newtonian fluid flows.Especially when the interface is close to the pipe wall,the power-law fluid flow may be unstable while the Newtonian fluid flow is stable.Second,under disturbances to the interface a velocity discontinuity at the interface appears which is destabilizing to the flow.The magnitude of this velocity discontinuity is affected by the power-law index and the flow stability is influenced correspondingly.Besides,the shear-thinning property may induce new stability modes which do not appear in the Newtonian fluid flow.The flow stability shows much dependence on the interface location,the role of which was neglected in most previous studies.The shear-thinning fluid flow is more unstable to long wave disturbances when the interface is close to the pipe wall,while the Newtonian fluid flow is more unstable when the interface is close to the pipe centerline.But this trend is changed by the addition of interfacial surfactant,for which the power-law fluid flow is more stable no matter where the interface is

  18. Performance model of metallic concentric tube recuperator with counter flow arrangement

    Science.gov (United States)

    Sharma, Harshdeep; Kumar, Anoop; Goel, Varun

    2010-03-01

    A performance model for counter flow arrangement in concentric tube recuperator that can be used to utilize the waste heat in the temperature range of 900-1,400°C is presented. The arrangement consists of metallic tubular inner and outer concentric shell with a small annular gap between two concentric shells. Flue gases pass through the inner shell while air passes through the annular gap in the reverse direction (counter flow arrangement). The height of the recuperator is divided into elements and an energy balance is performed on each elemental height. Results give necessary information about surface, gas and air temperature distribution, and the influence of operating conditions on recuperator performance. The recuperative effectiveness is found to be increased with increasing inlet gas temperature and decreased with increasing fuel flow rate. The present model accounts for all heat transfer processes pertinent to a counterflow radiation recuperator and provide a valuable tool for performance considerations.

  19. A comparison between numerical predictions and theoretical and experimental results for laminar core-annular flow

    NARCIS (Netherlands)

    Beerens, J.C.; Ooms, G.; Pourquie, M.J.B.M.; Westerweel, J.

    2014-01-01

    high-viscosity liquid core surrounded by a laminar low-viscosity liquid annular layer through a vertical pipe. The numerical results are compared with theoretical results from linear stability calculations and with experimental data. The comparison is good and the general conclusion of our study is

  20. A study on the effect of gas flow rate on the wave characteristics in two-phase gas-liquid annular flow

    Energy Technology Data Exchange (ETDEWEB)

    Han Huawei [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, Ont., L1H 7K4 (Canada)]. E-mail: colin.han@uoit.ca; Zhu Zhenfeng [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Sask., S7N 5A9 (Canada)]. E-mail: zhz752@mail.usask.ca; Gabriel, Kamiel [University of Ontario Institute of Technology, Oshawa, Ont., L1H 7K4 (Canada)]. E-mail: kamiel.gabriel@uoit.ca

    2006-12-15

    Interfacial waves play a very important role in the mass, momentum and energy transport phenomena in annular flow. In this paper, film thickness time-trace measurements for air-water annular flow were collected in a small vertical tube using a parallel wire probe. Using the data, a typical disturbance wave shape was obtained and wave properties (e.g., width, height, speed and roughness) were presented. The liquid mass flux ranged from 100 to 200 kg/m{sup 2} s and the gas mass flux ranged from 18 to 47 kg/m{sup 2} s. Disturbance wave characteristics were defined and the effects of changing the gas flow rate on the wave spacing, wave width, wave peak height and wave base height were studied. An average velocity model for the wave and base regions has been developed to determine the wave velocity. The investigation method could be further extended to annular-mist flow which frequently occurs in boiling water reactors.

  1. Heat and mass transfer for turbulent flow of chemically reacting gas in eccentric annular channels

    Science.gov (United States)

    Besedina, T. V.; Tverkovkin, B. E.; Udot, A. V.; Yakushev, A. P.

    1987-08-01

    An algorithm is proposed for calculating the velocity, temperature, and concentration fields under conditions of cooling of a cylindrical heat-releasing rod, placed off-center in a circular casing pipe, by a longitudinal flow of chemically reacting gas [N2O4].

  2. Analysis and generalization of experimental data on heat transfer to supercritical pressure water flow in annular channels and rod bundles

    Science.gov (United States)

    Deev, V. I.; Kharitonov, V. S.; Churkin, A. N.

    2017-02-01

    Experimental data on heat transfer to supercritical pressure water presented at ISSCWR-5, 6, and 7 international symposiums—which took place in 2011-2015 in Canada, China, and Finland—and data printed in recent periodical scientific publications were analyzed. Results of experiments with annular channels and three- and four-rod bundles of heating elements positioned in square or triangular grids were examined. Methodology used for round pipes was applied at generalization of experimental data and establishing of correlations suitable for engineering analysis of heat exchange coefficient in conditions of strongly changing water properties in the near-critical pressure region. Empiric formulas describing normal heat transfer to supercritical pressure water mowing in annular channels and rod bundles were obtained. As compared to existing recommendations, suggested correlations are distinguished by specified dependency of heat exchange coefficient on density of heat flux and mass flow velocity of water near pseudo-critical temperature. Differences between computed values of heat exchange coefficient and experimental data usually do not exceed ±25%. Detailed statistical analysis of deviations between computed and experimental results at different states of supercritical pressure water flow was carried out. Peculiarities of deteriorated heat exchange were considered and their existence boundaries were defined. Experimental results obtained for these regimes were generalized using criteria by J.D. Jackson that take the influence of thermal acceleration and Archimedes forces on heat exchange processes into account. Satisfactory agreement between experimental data on heat exchange at flowing of water in annular channels and rod bundles and data for round pipes was shown.

  3. Cold neutron tomography of annular coolant flow in a double subchannel model of a boiling water reactor

    Science.gov (United States)

    Kickhofel, J. L.; Zboray, R.; Damsohn, M.; Kaestner, A.; Lehmann, E. H.; Prasser, H.-M.

    2011-09-01

    Dryout of the liquid coolant film on fuel pins at the top of boiling water reactor (BWR) cores constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is a limiting factor in the thermal power, and therefore the economy, of BWRs. Ongoing research on multiphase annular flow, specifically the liquid film thickness, is fundamental not only to nuclear reactor safety and operation but also to that of evaporators, condensers, and pipelines in a general industrial context. We have performed cold neutron tomography of adiabatic air water annular flow in a scaled up model of the subchannel geometry found in BWR fuel assemblies today. All imaging has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institut in Switzerland. Neutron tomography is shown to excel in investigating the interactions of air water two phase flows with spacer vanes of different geometry. The high resolution, high contrast measurements provide spatial distributions of the coolant on top of the surfaces of the spacer, including the vanes, and in the subchannel downstream of the spacers.

  4. Evaluation of the rheological behavior of drilling fluids in annular flow conditions; Avaliacao do comportamento reologico de fluidos de perfuracao no escoamento anular

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Maria das Gracas Pena; Martins, Andre Leibsohn; Oliveira, Antonio Augusto Junqueira de [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas. Div. de Explotacao

    1988-12-31

    The rheological behavior of drilling fluids during annular flow in a physical simulator well (Surface Hydraulic System - SHS)was investigated. Measurement of volumetric flow and pressure drop the 10-meter simulator well was used to assess applicability of the Bingham, power Law, Casson, and Herschell-Bulkley models to the annular flow of water and oil-based fluids under different temperatures. Additionally, under different pre-set deformation ranges, SHS-observed behavior was compared with behavior observed using the traditional Fann VG 35 A viscometer. (author) 8 refs., 21 figs., 15 tabs.

  5. Nonlinear stability of oscillatory core-annular flow: A generalized Kuramoto-Sivashinsky equation with time periodic coefficients

    Science.gov (United States)

    Coward, Adrian V.; Papageorgiou, Demetrios T.; Smyrlis, Yiorgos S.

    1994-01-01

    In this paper the nonlinear stability of two-phase core-annular flow in a pipe is examined when the acting pressure gradient is modulated by time harmonic oscillations and viscosity stratification and interfacial tension is present. An exact solution of the Navier-Stokes equations is used as the background state to develop an asymptotic theory valid for thin annular layers, which leads to a novel nonlinear evolution describing the spatio-temporal evolution of the interface. The evolution equation is an extension of the equation found for constant pressure gradients and generalizes the Kuramoto-Sivashinsky equation with dispersive effects found by Papageorgiou, Maldarelli & Rumschitzki, Phys. Fluids A 2(3), 1990, pp. 340-352, to a similar system with time periodic coefficients. The distinct regimes of slow and moderate flow are considered and the corresponding evolution is derived. Certain solutions are described analytically in the neighborhood of the first bifurcation point by use of multiple scales asymptotics. Extensive numerical experiments, using dynamical systems ideas, are carried out in order to evaluate the effect of the oscillatory pressure gradient on the solutions in the presence of a constant pressure gradient.

  6. Pulsatile Flow through Annular Space Bounded by Outer Porous Cylinder and an Inner Cylinder of Permeable Material

    Science.gov (United States)

    Rashidi, M. M.; Keimanesh, M.; Rajvanshi, S. C.; Wasu, S.

    2012-10-01

    This study investigates the problem of pulsatile flow of an incompressible Newtonian fluid through annular space bounded by an outer porous cylinder and an inner cylinder of permeable material. The coupled flow has been analyzed by solving Navier-Stokes equations in the free fluid region and Darcy's equation in the porous region. Beaver-Joseph slip-condition has been used at the free fluid-permeable medium interface. The similarity transformation for the governing equations gives a system of nonlinear ordinary differential equations which are analytically solved by the homotopy analysis method (HAM). The analytical solutions have been obtained in the form of a series. An admissible interval for the convergence of the series solutions has been indicated. Graphical results are presented to show the influence of different parameters on velocity profiles, pressure drop, and skin friction. Comparison between the solutions obtained by the HAM and the numerical solution shows good agreement.

  7. Influence of air flow parameters on nanosecond repetitively pulsed discharges in a pin-annular electrode configuration

    KAUST Repository

    Heitz, Sylvain A

    2016-03-16

    The effect of various air flow parameters on the plasma regimes of nanosecond repetitively pulsed (NRP) discharges is investigated at atmospheric pressure. The two electrodes are in a pin-annular configuration, transverse to the mean flow. The voltage pulses have amplitudes up to 15 kV, a duration of 10 ns and a repetition frequency ranging from 15 to 30 kHz. The NRP corona to NRP spark (C-S) regime transition and the NRP spark to NRP corona (S-C) regime transition are investigated for different steady and harmonically oscillating flows. First, the strong effect of a transverse flow on the C-S and S-C transitions, as reported in previous studies, is verified. Second, it is shown that the azimuthal flow imparted by a swirler does not affect the regime transition voltages. Finally, the influence of low frequency harmonic oscillations of the air flow, generated by a loudspeaker, is studied. A strong effect of frequency and amplitude of the incoming flow modulation on the NRP plasma regime is observed. Results are interpreted based on the cumulative effect of the NRP discharges and an analysis of the residence times of fluid particles in the inter-electrode region. © 2016 IOP Publishing Ltd.

  8. Study of secondary-flow patterns in an annular cascade of turbine nozzle blades with vortex design

    Science.gov (United States)

    Rohlik, Harold E; Allen, Hubert W; Herzig, Howard Z

    1953-01-01

    In order to increase understanding of the origin of losses in a turbine, the secondary-flow components in the boundary layers and the blade wakes of an annular cascade of turbine nozzle blades (vortex design) was investigated. A detailed study was made of the total-pressure contours and, particularly, of the inner-wall loss cores downstream of the blades. The inner-wall loss core associated with a blade of the turbine-nozzle cascade is largely the accumulation of low-momentum fluids originating elsewhere in the cascade. This accumulation is effected by a secondary-flow mechanism which acts to transport the low-momentum fluids across the channels on the walls and radially in the blade wakes and boundary layers. The patterns of secondary flow were determined by use of hydrogen sulfide traces, paint, flow fences, and total pressure surveys. At one flow condition investigated, the radial transport of low-momentum fluid in the blade wake and on the suction surface near the trailing edge accounted for 65 percent of the loss core; 30 percent resulted from flow in the thickened boundary layer on the suction surface and 35 percent from flow in the blade wake.

  9. An Experimental Study on 3—D Flow in an Annular Cascade of High Turning Angle Turbine Blades

    Institute of Scientific and Technical Information of China (English)

    WangWensheng; LiangXizhi; 等

    1994-01-01

    This paper presents an experimental study of the three-dimensional turbulent flow fields in a lowspeed annular cascade of high turning angle turbine blades.Detailed measurements were performed on the blade surfaces and mid-streamsurface in the passage and at three axial planes downstream of the cascade by using wall static pressure taps,a five-hole probe and a hot-wire anemometer,The test data include static pressure distribution on blade surfaces,total pressure loss cofeeicient,mean flow velocity components.radial flow angle,turbulence intensity and Reynolds shear stress.Analyses of the three-dimensional cascade flow characteristics were made on the noset location of high loss vortices.the variation of pressure gradient inside the cascade passage and the properties of endwall boundary layers total pressure loss distributions,secondary vortex turbulent dissipation and wake decay downtream of the cascade.These experimental results are valuable for revealing the details of the complex vortex flow structure in modern highly loaded axial turbomachines and validating the three-dimensional flow numerical computation codes.

  10. Influence of a flow obstacle on the occurrence of burnout in boiling two-phase upward flow within a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Mori, S.; Fukano, T. [Kyushu Univ., Fukuoka (Japan)

    2003-07-01

    When a flow obstruction such as a cylindrical spacer is set in a boiling two-phase flow with-in an annular channel, the inner tube of which is used as a heater, the temperature on the surface of the heating tube is severely affected by its existence. In some cases the cylindrical spacer has a cooling effect, and in the other cases it causes the dryout of the cooling water film on the heating surface resulting in the burnout of the heating tube. In the present paper we have focused our attention on the influence of a flow obstacle on the occurrence of burnout of the heating tube in boiling two-phase flow.

  11. A study of the flow boiling heat transfer in an annular heat exchanger with a mini gap

    Directory of Open Access Journals (Sweden)

    Musiał Tomasz

    2017-01-01

    Full Text Available In this paper the research on flow boiling heat transfer in an annular mini gap was discussed. A one- dimensional mathematical approach was proposed to describe stationary heat transfer in the gap. The mini gap 1 mm wide was created between a metal pipe with enhanced exterior surface and an external tempered glass pipe positioned along the same axis. The experimental test stand consists of several systems: the test loop in which distilled water circulates, the data and image acquisition system and the supply and control system. Known temperature distributions of the metal pipe with enhanced surface and of the working fluid helped to determine, from the Robin boundary condition, the local heat transfer coefficients at the fluid - heated surface contact. In the proposed mathematical model it is assumed that the cylindrical wall is a planar multilayer wall. The numerical results are presented on a chart as function of the heat transfer coefficient along the length of the mini gap.

  12. Immiscible displacement of oil by water in a microchannel: Asymmetric flow behavior and nonlinear stability analysis of core-annular flow

    Science.gov (United States)

    Foroughi, Hooman; Abbasi, Alireza; Das, Kausik S.; Kawaji, Masahiro

    2012-02-01

    The immiscible displacement of oil by water in a circular microchannel was investigated. A fused silica microchannel with an inner diameter of 250 μm and a length of 7 cm was initially filled with a viscous silicone oil. Only water then was injected into the channel. We describe our flow observations based on the two-dimensional images captured in the middle of the channel. The water finger displaced the oil and left an oil film on the channel wall. While the oil was being displaced at the core, the flow resistance decreased, which resulted in increases in water flow rate and inertia. Eventually, the water finger reached the channel exit and formed a core-annular flow pattern. The wavelength of the waves formed at the oil-water interface also increased with the increase in inertia. The initially symmetric interfacial waves became asymmetric with time. Also, the water core shifted from the center of the channel and left a thinner oil film on one side of the microchannel. Under all flow rates tested in this study, as long as the water was continuously injected, the water core was stable and no breakup into droplets was observed. We also discuss the flow stability based on nonlinear and linear stability analyses performed on the core-annular flow. Compared to the linear analysis, which ignores the inertia effects, the nonlinear analysis, which includes the inertia effects, predicts longer interfacial wavelengths by a factor of (1)/(1-(ao)/(2)(Wew+Weo(ao2)/(1-ao2))) where Wew and Weo are the Weber numbers of the water and the oil phases, respectively, and ao is the unperturbed water core radius made dimensionless by the channel radius.

  13. Immiscible displacement of oil by water in a microchannel: asymmetric flow behavior and nonlinear stability analysis of core-annular flow.

    Science.gov (United States)

    Foroughi, Hooman; Abbasi, Alireza; Das, Kausik S; Kawaji, Masahiro

    2012-02-01

    The immiscible displacement of oil by water in a circular microchannel was investigated. A fused silica microchannel with an inner diameter of 250 μm and a length of 7 cm was initially filled with a viscous silicone oil. Only water then was injected into the channel. We describe our flow observations based on the two-dimensional images captured in the middle of the channel. The water finger displaced the oil and left an oil film on the channel wall. While the oil was being displaced at the core, the flow resistance decreased, which resulted in increases in water flow rate and inertia. Eventually, the water finger reached the channel exit and formed a core-annular flow pattern. The wavelength of the waves formed at the oil-water interface also increased with the increase in inertia. The initially symmetric interfacial waves became asymmetric with time. Also, the water core shifted from the center of the channel and left a thinner oil film on one side of the microchannel. Under all flow rates tested in this study, as long as the water was continuously injected, the water core was stable and no breakup into droplets was observed. We also discuss the flow stability based on nonlinear and linear stability analyses performed on the core-annular flow. Compared to the linear analysis, which ignores the inertia effects, the nonlinear analysis, which includes the inertia effects, predicts longer interfacial wavelengths by a factor of 1/sqrt[1-a(o)/2(We(w) + We(o)a(o)(2)/1-a(o)(2))] where We(w) and We(o) are the Weber numbers of the water and the oil phases, respectively, and a(o) is the unperturbed water core radius made dimensionless by the channel radius.

  14. Application of bismuth bulk annular band electrode for determination of ultratrace concentrations of thallium(I) using stripping voltammetry.

    Science.gov (United States)

    Węgiel, Krystian; Jedlińska, Katarzyna; Baś, Bogusław

    2016-06-05

    A study of a new type of mercury-free working electrode - the bismuth bulk annular band working electrode (BiABE) - applied for thallium(I) detection via differential pulse anodic stripping voltammetry (DP ASV), preceded by the complexation of interfering ions (Cd(2+), Pb(2+)) with EDTA in an acetate buffer (pH 4.5), is reported. The optimisation of experimental conditions included selection of the appropriate supporting electrolyte solution, potential and time of preconcentration, and DP mode parameters. The peak current was proportional to the concentration of Tl(I) in the range from 0.5 to 49nmolL(-1) (R=0.9992) and from 0.05 to 1.4nmolL(-1) (R=0.9987) for accumulation times of 60s and 300s, respectively. For 60s of accumulation time, the LOD was 0.005nmolL(-1) (1ngL(-1)) (at S/N=3), and the sensitivity of 18.5nA/nM was achieved. The relative standard deviation for 4.9nmolL(-1) of Tl(I) was 4.3% (n=5). Finally, the proposed method was successfully applied to determine Tl(I) in the certified reference materials-waters (SPS-SW1 and SPS-SW2) as well as the spiked tap and river water samples.

  15. 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.

  16. Flow Characteristic Study in a Configuration of Sudden Expansion with Central Restriction and Fence – Viewed as an Annular Flow Dump Combustor

    Directory of Open Access Journals (Sweden)

    Tridibesh Das

    2015-01-01

    Full Text Available In this paper, a numerical study on flow characteristics in configurations of sudden expansion with central restriction and fence viewed as annular flow dump combustor has been carried out for Reynolds number (Re ranging from 50 to 200, percentage of central restriction (CR from 10% to 40% and aspect ratio (AR from 2 to 6 with a fixed fence subtended angle (FSA of 10 degree and with a fixed distance of fence from throat respectively. The effect of each variable on streamline contour and velocity profile has been studied in detail. Results have been compared with the configuration of sudden expansion with central restriction only. From the study it is concluded that the configuration of sudden expansion with central restriction and fence with higher flow Reynolds number, higher central restriction and higher aspect ratio offers more benefit in terms of the mixing possibility compared to the case of sudden expansion with central restriction only.

  17. Dynamic characteristics of an eccentric finite-length large gap annular flow%偏心有限长大间隙环流的动特性研究

    Institute of Scientific and Technical Information of China (English)

    孙启国

    2011-01-01

    Based on a 3D mechanical model for a large gap annular flow developed by authors, the zero-order perturbation equations of 3D non-linear partial differential equations for the motion of an eccentric rotor in a finite-length large gap annular flow were derived here. The zero-order perturbation equations were also 3D non-linear partial differential equations, and there was a little difficulty to get their solutions. Therefore, a simplified numerical method based on the results of a finite-length concentric large gap annular flow analyzed by authors before, was put forward in order to analyze the dynamic coefficients of the eccentric rotor in the finite-length large gap annular flow. Comparing with the existing numerical results and testing ones, it was shown that this method is sufficient and accurate. Numerical results showed that the dynamic coefficients of the eccentric rotor in the finite-length large gap annular flow have no features that the main terms are equal, the coupled terms are equal and opposite, comparing with those of the concentric rotor in the finite-length large gap annular flow; all main terms of the dynamic coefficients increase exponentially with increase in eccentricity rate, this means that the dynamic coefficients of an eccentric rotor in a finite-length large gap annular flow increase greatly with a large eccentricity.%基于所建立的大间隙环流中转子运动的三维力学模型,用摄动法推导了有限长大间隙环流流场非线性控制方程的零阶摄动方程组.该方程组是一个复杂的三维非线性偏微分方程组,其求解有一定的困难.为此,提出了一种简化数值方法.该简化方法是采用作者以前获得的同心有限长大间隙环流的动特性系数来计算三维偏心有限长大间隙环流的动特性系数.与已有的数值计算结果和实验结果比较,该简化方法具有较好的实用性和精度.数值计算结果表明与同心有限长大间隙环流相比,偏心有

  18. Acoustic concentration of particles in fluid flow

    Science.gov (United States)

    Ward, Michael D.; Kaduchak, Gregory

    2010-11-23

    An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  19. Acoustic concentration of particles in fluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Michael W.; Kaduchak, Gregory

    2017-08-15

    Disclosed herein is a acoustic concentration of particles in a fluid flow that includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  20. Experimental development of a Nusselt correlation for forced reciprocating oscillated vertical annular glycerol flow through a porous domain

    Science.gov (United States)

    Sayar, Ersin

    2017-02-01

    The objective of this paper is to investigate the heat transfer to oscillating annular flow of a viscous fluid. The flow media includes stationary stainless steel wool porous domain and glycerol as the working fluid. The effects of actuation frequency and wall heat flux on the temperature field and resultant heat convection coefficient are studied. The temperature values at radial direction are close each other as porous media mixes the glycerol successfully. A correlation with a functional dependence to kinetic Reynolds number is recommended that can be used to acquire the averaged heat transfer for oscillating flows. Present experimental results with glycerol in a porous media are compared to the published experimental works with water. For the limited case of the two working fluids, Nusselt number is normalized well using the Prandtl number (Pr0.67). Results are also compared to non-porous media study and heat transfer is found to increase up to a factor of five in porous media. The recommended correlation is claimed to have a significant role for anticipating heat transfer of oscillating viscous fluid not only at low frequencies but also at low heat fluxes in a porous and permeable solid media.

  1. The axisymmetric long-wave interfacial stability of core-annular flow of power-law fluid with surfactant

    Institute of Scientific and Technical Information of China (English)

    Xue-Wei Sun; Jie Peng; Ke-Qin Zhu

    2012-01-01

    The long wave stability of core-annular flow of power-law fluids with an axial pressure gradient is investigated at low Reynolds number.The interface between the two fluids is populated with an insoluble surfactant.The analytic solution for the growth rate of perturbation is obtained with long wave approximation.We are mainly concerned with the effects of shear-thinning/thickening property and interfacial surfactant on the flow stability.The results show that the influence of shear-thinning/thickening property accounts to the change of the capillary number.For a clean interface,the shear-thinning property enhances the capillary instability when the interface is close to the pipe wall.The converse is true when the interface is close to the pipe centerline.For shear-thickening fluids,the situation is reversed.When the interface is close to the pipe centerline,the capillary instability can be restrained due to the influence of surfactant.A parameter set can be found under which the flow is linearly stable.

  2. Laser anemometer measurements and computations for transonic flow conditions in an annular cascade of high turning core turbine vanes

    Science.gov (United States)

    Goldman, Louis J.

    1993-01-01

    An advanced laser anemometer (LA) was used to measure the axial and tangential velocity components in an annular cascade of turbine stator vanes operating at transonic flow conditions. The vanes tested were based on a previous redesign of the first-stage stator in a two-stage turbine for a high-bypass-ratio engine. The vanes produced 75 deg of flow turning. Tests were conducted on a 0.771-scale model of the engine-sized stator. The advanced LA fringe system employed an extremely small 50-micron diameter probe volume. Window correction optics were used to ensure that the laser beams did not uncross in passing through the curved optical access port. Experimental LA measurements of velocity and turbulence were obtained at the mean radius upstream of, within, and downstream of the stator vane row at an exit critical velocity ratio of 1.050 at the hub. Static pressures were also measured on the vane surface. The measurements are compared, where possible, with calculations from a three-dimensional inviscid flow analysis. Comparisons were also made with the results obtained previously when these same vanes were tested at the design exit critical velocity ratio of 0.896 at the hub. The data are presented in both graphical and tabulated form so that they can be readily compared against other turbomachinery computations.

  3. 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.

  4. Optimal design of high damping force engine mount featuring MR valve structure with both annular and radial flow paths

    Science.gov (United States)

    Nguyen, Q. H.; Choi, S. B.; Lee, Y. S.; Han, M. S.

    2013-11-01

    This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption.

  5. Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

    Directory of Open Access Journals (Sweden)

    Nili-Ahmadabadi M.

    2012-01-01

    Full Text Available This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000flow characteristics.

  6. Analytical study of flow and heat transfer in an annular porous medium subject to asymmetrical heat fluxes

    Science.gov (United States)

    Xu, Huijin; Zhao, Changying; Vafai, Kambiz

    2017-08-01

    Fully developed forced convective heat transfer in an annulus filled with a porous medium subject to asymmetrical heating is investigated analytically with different models in this work. The classic Darcy and Brinkman models were employed for the fluid flow, while the local thermal equilibrium (LTE) and the local thermal non-equilibrium (LTNE) models were employed to describe the heat transfer process in porous media. An analytical model based on fin theory was also employed for analyzing this problem. Exact solutions with Darcy-LTNE, Darcy-LTE, Brinkman-LTNE, Brinkman-LTE, and the fin models were obtained. Among these solutions, the Brinkman-LTNE solution can be treated as the benchmark, as it is a complete model, which covers the effect of viscous force near the solid wall and the temperature difference between the solid and fluid phases. The basic parameters that affect the velocity and temperature fields were analyzed in depth. The velocity and temperature profiles with these different models were also presented. The effects of some critical parameters on thermal performance of asymmetrically heated annulus fitted with a porous medium were discussed. The cited different analytical models were compared in detail with each other. The critical heat flux (HF) ratios for the inner and outer walls were presented in terms of a Nu- ξ curve for the five models. These solutions were developed for an asymmetrically heated annular channel filled with a porous medium, which can predict the thermal performance within a wide range of radii and HF ratios.

  7. Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial δ-doped diamond layers

    Energy Technology Data Exchange (ETDEWEB)

    Araújo, D.; Alegre, M. P.; Piñero, J. C. [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain); Fiori, A.; Bustarret, E. [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France); Jomard, F. [Groupe d' Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)

    2013-07-22

    To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 10{sup 20} cm{sup −3} were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p{sup −}/p{sup ++}/p{sup −} multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.

  8. Multiple annular linear diffractive axicons.

    Science.gov (United States)

    Bialic, Emilie; de la Tocnaye, Jean-Louis de Bougrenet

    2011-04-01

    We propose a chromatic analysis of multiple annular linear diffractive axicons. Large aperture axicons are optical devices providing achromatic nondiffracting beams, with an extended depth of focus, when illuminated by a white light source, due to chromatic foci superimposition. Annular apertures introduce chromatic foci separation, and because chromatic aberrations result in focal segment axial shifts, polychromatic imaging properties are partially lost. We investigate here various design parameters that can be used to achieve color splitting, filtering, and combining using these properties. In order to improve the low-power efficiency of a single annular axicon, we suggest a spatial multiplexing of concentric annular axicons with different sizes and periods we call multiple annular aperture diffractive axicons (MALDAs). These are chosen to maintain focal depths while enabling color imaging with sufficient diffraction efficiency. Illustrations are given for binary phase diffractive axicons, considering technical aspects such as grating design wavelength and phase dependence due to the grating thickness.

  9. Influence of a flow obstacle on the occurrence of burnout in boiling two-phase upward flow within a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Mori, S.; Fukano, T. E-mail: fukanot@mech.kyushu-u.ac.jp

    2003-10-01

    When a flow obstruction such as a cylindrical spacer is set in a boiling two-phase flow within an annular channel, the inner tube of which is used as a heater, the temperature on the surface of the heating tube is severely affected by its existence. In some cases, the cylindrical spacer has a cooling effect, and in the other cases it causes the dryout of the cooling water film on the heating surface resulting in the burnout of the heating tube. In the present paper, we have focused our attention on the influence of a flow obstacle on the occurrence of burnout of the heating tube in boiling two-phase flow. The results are summarized as follows: - When the heat flux approaches the burnout condition, the wall temperature on the heating tube fluctuates with a large amplitude. And once the wall temperature exceeds the Leidenfrost temperature, the burnout occurs without exception. - The trigger of dryout of the water film which causes the burnout is not the nucleate boiling but the evaporation of the base film between disturbance waves. - The burnout never occurs at the downstream side of the spacer. This is because the dryout area downstream of the spacer is rewetted easily by the disturbance waves.

  10. Oscillatory and Steady Flows in the Annular Fluid Layer inside a Rotating Cylinder

    Directory of Open Access Journals (Sweden)

    Veronika Dyakova

    2016-01-01

    Full Text Available The dynamics of a low-viscosity fluid inside a rapidly rotating horizontal cylinder were experimentally studied. In the rotating frame, the force of gravity induces azimuthal fluid oscillations at a frequency equal to the velocity of the cylinder’s rotation. This flow is responsible for a series of phenomena, such as the onset of centrifugal instability in the Stokes layer and the growth of the relief at the interface between the fluid and the granular medium inside the rotating cylinder. The phase inhomogeneity of the oscillatory fluid flow in the viscous boundary layers near the rigid wall and the free surface generates the azimuthal steady streaming. We studied the relative contribution of the viscous boundary layers in the generation of the steady streaming. It is revealed that the velocity of the steady streaming can be calculated using the velocity of the oscillatory fluid motion.

  11. Generation of Turbulent Inflow Conditions for Pipe Flow via an Annular Ribbed Turbulator

    Science.gov (United States)

    Moallemi, Nima; Brinkerhoff, Joshua

    2016-11-01

    The generation of turbulent inflow conditions adds significant computational expense to direct numerical simulations (DNS) of turbulent pipe flows. Typical approaches involve introducing boxes of isotropic turbulence to the velocity field at the inlet of the pipe. In the present study, an alternative method is proposed that incurs a lower computational cost and allows the anisotropy observed in pipe turbulence to be physically captured. The method is based on a periodic DNS of a ribbed turbulator upstream of the inlet boundary of the pipe. The Reynolds number based on the bulk velocity and pipe diameter is 5300 and the blockage ratio (BR) is 0.06 based on the rib height and pipe diameter. The pitch ratio is defined as the ratio of rib streamwise spacing to rib height and is varied between 1.7 and 5.0. The generation of turbulent flow structures downstream of the ribbed turbulator are identified and discussed. Suitability of this method for accurate representation of turbulent inflow conditions is assessed through comparison of the turbulent mean properties, fluctuations, Reynolds stress profiles, and spectra with published pipe flow DNS studies. The DNS results achieve excellent agreement with the numerical and experimental data available in the literature.

  12. Buddly, slug, and annular two-phase flow in tight-lattice subchannels

    Energy Technology Data Exchange (ETDEWEB)

    Prasser, Horst-Michael; Bolesch, Charistian; Cramer, Kerstin; Papadopoulos, Petros; Saxena, Abhishek; Zboray, Robert [ETH Zurich, Dept. of Mechanical and Process Engineering (D-MAVT), Zurich (Switzerland); Ito, Daisuke [Kyoto University, Research Reactor Institute, Osaka (Japan)

    2016-08-15

    An overview is given on the work of the Laboratory of Nuclear Energy Systems at ETH, Zurich (ETHZ) and of the Laboratory of Thermal Hydraulics at Paul Scherrer Institute (PSI), Switzerland on tight-lattice bundles. Two-phase flow in subchannels of a tight triangular lattice was studied experimentally and by computational fluid dynamics simulations. Two adiabatic facilities were used: (1) a vertical channel modeling a pair of neighboring subchannels; and (2) an arrangement of four subchannels with one subchannel in the center. The first geometry was equipped with two electrical film sensors placed on opposing rod surfaces forming the subchannel gap. They recorded 2D liquid film thickness distributions on a domain of 16 × 64 measuring points each, with a time resolution of 10 kHz. In the bubbly and slug flow regime, information on the bubble size, shape, and velocity and the residual liquid film thickness underneath the bubbles were obtained. The second channel was investigated using cold neutron tomography, which allowed the measurement of average liquid film profiles showing the effect of spacer grids with vanes. The results were reproduced by large eddy simulation + volume of fluid. In the outlook, a novel nonadiabatic subchannel experiment is introduced that can be driven to steady-state dryout. A refrigerant is heated by a heavy water circuit, which allows the application of cold neutron tomography.

  13. Bubbly, Slug, and Annular Two-Phase Flow in Tight-Lattice Subchannels

    Directory of Open Access Journals (Sweden)

    Horst-Michael Prasser

    2016-08-01

    Full Text Available An overview is given on the work of the Laboratory of Nuclear Energy Systems at ETH, Zurich (ETHZ and of the Laboratory of Thermal Hydraulics at Paul Scherrer Institute (PSI, Switzerland on tight-lattice bundles. Two-phase flow in subchannels of a tight triangular lattice was studied experimentally and by computational fluid dynamics simulations. Two adiabatic facilities were used: (1 a vertical channel modeling a pair of neighboring subchannels; and (2 an arrangement of four subchannels with one subchannel in the center. The first geometry was equipped with two electrical film sensors placed on opposing rod surfaces forming the subchannel gap. They recorded 2D liquid film thickness distributions on a domain of 16 × 64 measuring points each, with a time resolution of 10 kHz. In the bubbly and slug flow regime, information on the bubble size, shape, and velocity and the residual liquid film thickness underneath the bubbles were obtained. The second channel was investigated using cold neutron tomography, which allowed the measurement of average liquid film profiles showing the effect of spacer grids with vanes. The results were reproduced by large eddy simulation + volume of fluid. In the outlook, a novel nonadiabatic subchannel experiment is introduced that can be driven to steady-state dryout. A refrigerant is heated by a heavy water circuit, which allows the application of cold neutron tomography.

  14. An empirical investigation on thermal characteristics and pressure drop of Ag-oil nanofluid in concentric annular tube

    Science.gov (United States)

    Abbasian Arani, A. A.; Aberoumand, H.; Aberoumand, S.; Jafari Moghaddam, A.; Dastanian, M.

    2016-08-01

    In this work an experimental study on Silver-oil nanofluid was carried out in order to present the laminar convective heat transfer coefficient and friction factor in a concentric annulus with constant heat flux boundary condition. Silver-oil nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. The average sizes of particles were 20 nm. Nanofluids with various particle Volume fractions of 0.011, 0.044 and 0.171 vol% were employed. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as flow Reynolds number, tube diameter ratio and nanofluid particle concentration on heat transfer coefficient are studied. Results show that, heat transfer coefficient increased by using nanofluid instead of pure oil. Maximum enhancement of heat transfer coefficient occurs in 0.171 vol%. In addition the results showed that, there are slight increases in pressure drop of nanofluid by increasing the nanoparticle concentration of nanofluid in compared to pure oil.

  15. An experimental study on counter current flow limitation in annular narrow gaps with large diameter

    Energy Technology Data Exchange (ETDEWEB)

    Park, Rae Joon; Jeong, Ji Whan; Lee, Sung Jin; Cho, Young Ro; Ha, Kwang Sun; Kim, Sang Baik; Kim, Hee Dong [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-04-01

    The present study intends to carry out CCFL experiment with the same gap size as the CHFG facility and suggest an empirical correlation in order to provide basic information useful to development of an empirical critical-power correlation. The present facility consists of water accumulator tank, test section, DC pump, air regulator, valves and sensors. Air and water are used as working fluids. The experiments are carried out at the atmospheric pressure. Differential pressure between the gap ends, liquid and gas phase flow rates, temperature, lower plenum pressure are measured.Measured values are expressed in terms of Wallis' parameter using gap size as a characteristic length. There is a big difference between the present experimental results and the Koizumi et al.'s results, but the present experimental results are very similar to the Richter et al.'s results. The present results agree well with the Osakabe and Kawasaki's results. In comparison of present experiments with the Koizumi et al.'s experiments, gap thickness is similar, but the diameter of the present is bigger than that of Koizumi et al.'s experiments. In comparison of present experiments with the Richter et al.'s experiments, diameter is similar, but the gap thickness of the present is smaller than that of Richter et al.'s experiments. It is judged from these results that correlation development on CCFL to consider gap thickness is reasonable at similar condition of diameter.The developed correlation will be used to develop the CHFG model. 36 refs., 26 figs., 7 tabs. (Author)

  16. Active Control of Fan Noise: Feasibility Study. Volume 6; Theoretical Analysis for Coupling of Active Noise Control Actuator Ring Sources to an Annular Duct with Flow

    Science.gov (United States)

    Kraft, R. E.

    1996-01-01

    The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the

  17. On the occurrence of burnout downstream of a flow obstacle in boiling two-phase upward flow within a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Shoji [Yokohama National University, Yokohama 240-8501 (Japan)], E-mail: morisho@ynu.ac.jp; Tominaga, Akira [Ube National College of Technology, Ube 755-8555 (Japan)], E-mail: tominaga@ube-k.ac.jp; Fukano, Tohru [Kurume Institute of University, Fukuoka 830-0052 (Japan)], E-mail: fukanot@cc.kurume-it.ac.jp

    2007-12-15

    If a flow obstacle, such as a spacer is placed in a boiling two-phase flow within a channel, the temperature on the surface of the heating tube is severely affected by the existence of the spacer. Under certain conditions, a spacer has a cooling effect, and under other conditions, the spacer causes dryout of the cooling water film on the heating surface. The burnout mechanism, which always occurs upstream of a spacer, however, remains unclear. In a previous paper [Fukano, T., Mori, S., Akamatsu, S., Baba, A., 2002. Relation between temperature fluctuation of a heating surface and generation of drypatch caused by a cylindrical spacer in a vertical boiling two-phase upward flow in a narrow annular channel. Nucl. Eng. Des. 217, 81-90], we reported that the disturbance wave has a significant effect on dryout and burnout occurrence and that a spacer greatly affects the behavior of the liquid film downstream of the spacer. In the present study, we examined in detail the influences of a spacer on the heat transfer and film thickness characteristics downstream of the spacer by considering the result in steam-water and air-water systems. The main results are summarized as follows: (1)The spacer averages the liquid film in the disturbance wave flow. As a result, dryout tends not to occur downstream of the spacer. This means that large temperature increases do not occur there. However, traces of disturbance waves remain, even if the disturbance waves are averaged by the spacer. (2)There is a high probability that the location at which burnout occurs is upstream of the downstream spacer, irrespective of the spacer spacing. (3)The newly proposed burnout occurrence model can explain the phenomena that burnout does occur upstream of the downstream spacer, even if the liquid film thickness t{sub Fm} is approximately the same before and behind the spacer.

  18. Annular recuperator design

    Science.gov (United States)

    Kang, Yungmo

    2005-10-04

    An annular heat recuperator is formed with alternating hot and cold cells to separate counter-flowing hot and cold fluid streams. Each cold cell has a fluid inlet formed in the inner diameter of the recuperator near one axial end, and a fluid outlet formed in the outer diameter of the recuperator near the other axial end to evenly distribute fluid mass flow throughout the cell. Cold cells may be joined with the outlet of one cell fluidly connected to the inlet of an adjacent downstream cell to form multi-stage cells.

  19. Annular-Cross-Section CFE Chamber

    Science.gov (United States)

    Sharnez, Rizwan; Sammons, David W.

    1994-01-01

    Proposed continuous-flow-electrophoresis (CFE) chamber of annular cross section offers advantages over conventional CFE chamber, and wedge-cross-section chamber described in "Increasing Sensitivity in Continuous-Flow Electrophoresis" (MFS-26176). In comparison with wedge-shaped chamber, chamber of annular cross section virtually eliminates such wall effects as electro-osmosis and transverse gradients of velocity. Sensitivity enhanced by incorporating gradient maker and radial (collateral) flow.

  20. Relation between burnout and differential pressure fluctuation characteristics by the disturbance waves near the flow obstacle in a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Shoji; Fukano, Tohru [Kyushu Univ., Graduate School of Engineering, Fukuoka (Japan)

    2002-07-01

    If a flow obstruction such as a spacer is set in a boiling two-phase flow within an annular channel, the inner tube of which is used as a heater, the temperature on the surface of the heater tube is severely affected by the existence of the spacer. In some cases the spacer has a cooling effect, and in the other case it causes the dryout of the cooling liquid film on the heating surface resulting in the burnout of the tube. But the thermo-fluid dynamic mechanism to cause burnout near the spacer is not still clear. In the present paper we discuss temperature fluctuation characteristics in relation to the change of the differential pressure across the spacer caused by the passing of the disturbance waves in case that the burnout generates. (author)

  1. Flow line asymmetric nonimaging concentrating optics

    Science.gov (United States)

    Jiang, Lun; Winston, Roland

    2016-09-01

    Nonimaging Optics has shown that it achieves the theoretical limits by utilizing thermodynamic principles rather than conventional optics. Hence in this paper the condition of the "best" design are both defined and fulfilled in the framework of thermodynamic arguments, which we believe has profound consequences for the designs of thermal and even photovoltaic systems, even illumination and optical communication tasks. This new way of looking at the problem of efficient concentration depends on probabilities, geometric flux field and radiative heat transfer while "optics" in the conventional sense recedes into the background. Some of the new development of flow line designs will be introduced and the connection between the thermodynamics and flow line design will be officially formulated in the framework of geometric flux field. A new way of using geometric flux to design nonimaging optics will be introduced. And finally, we discuss the possibility of 3D ideal nonimaing optics.

  2. 竖直窄矩形通道内环状流的流动传热特性%Flow and heat transfer characteristics of annular flow in vertical rectangular narrow channel

    Institute of Scientific and Technical Information of China (English)

    陈冲; 高璞珍; 谭思超; 余志庭; 陈先兵

    2015-01-01

    为了研究竖直窄矩形通道内环状流的流动传热特性,建立了窄矩形通道内环状流的数学物理模型,并进行了实验验证。通过数值求解环状流的数学物理模型得到了环状流区域的压降梯度、沸腾传热系数和液膜内的速度分布。结果表明窄矩形通道内的环状流模型能够很好地预测环状流区域的压降梯度和沸腾传热系数,而且环状流液膜内速度在法向的分布是非线性的,在层流边界层区速度梯度较大。热通量和窄矩形通道的尺寸对液膜的流速有很大影响,随热通量的增加和窄矩形通道尺寸的减小液膜的流速逐渐增加,然而质量流速对液膜流速的影响较小,而且随质量流速的增加液膜的速度逐渐减小。%A mathematical model of annular flow in vertical rectangular narrow channel was developed and experimental verification was performed in order to study flow and heat transfer characteristics of annular flow in vertical rectangular narrow channel. Through numerically solving the mathematical model, pressure gradient, boiling heat transfer and liquid film velocity profile in the annular flow region were obtained. The present model could well predict pressure gradient and boiling heat transfer. The liquid film velocity profile of annular flow in the normal direction was not linear, and liquid film velocity gradient was large in the laminar boundary layer. Rectangular narrow channel size and heat flux had significant effect on liquid film velocity profile. Liquid film velocity increased with increasing heat flux and decreased with increasing channel size. The effect of mass flow rate on liquid film velocity was smaller than the effect of heat flux and channel size, and liquid film velocity decreased with increasing mass flow rate.

  3. Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model. M.S. Thesis, Final Report

    Science.gov (United States)

    Dwenger, Richard Dale

    1995-01-01

    An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

  4. Magnetohydrodynamic Flow Between Concentric Rotating Porous Cylinders

    Directory of Open Access Journals (Sweden)

    S. N. Dube

    1971-10-01

    Full Text Available An attempt has been made to study the steady laminar flow of a incompressible electrically conducting fluid between infinitely long concentric rotating porous cylinders under the influence of radial magnetic field. A solution has been obtained under the assumption of uniform conditions along the axis of the cylinders. The cylinders being porous, a hyperbolic radial velocity distribution has been superimposed over the circumferential velocity produced due to rotation. There is a Bernoulli type pressure variation in the radial in the direction. When the inner cylinder is at rest the shearing stress at it and the torque transmitted to it decrease as R (=v/Sub/1y/Sub1/v= v/Sub2y/Sub2/v increases and the magnetic parameter lambda (=4sigma mue/sube/sup2A/Sup2/Mue will further decrease them.

  5. Evaluation of drilling fluids flow regime in annular sections; Avaliacao do regime de escoamento de fluidos de perfuracao em secoes anulares

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Maria das Gracas Pena [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas. Setor de Tecnologia de Perfuracao

    1989-12-31

    The determination of the transition zone between the laminar and turbulent flow regimes of particular importance in optimizing the hydraulics of drilling operations. The principal advantage which laminar flow in the annular space has in drilling operations in the avoidance of wall enlargement (wash-outs), maintaining formation integrity as much as possible. On the other hand, a lower-energy regime such as laminar flow does not provide the same cuttings-carrying capacity as that obtained when the drilling fluid is in turbulent flow. However, to be able to optimize the hydraulics it is necessary to have determined, among other parameters, the transition zone, in order to maximize the drilling rate while obtaining the hole clear of cuttings and maintaining the hole diameter constant over the whole of the section drilled. This paper presents, based on experimental results obtained on the SHS physical simulator, the transition zone expressed through the critical Reynolds numbers and those for low stable turbulence of various drilling fluids tested over the temperature range of 25-80 deg C. (author) 20 refs., 7 figs., 4 tabs.

  6. 化学激光器环形与线形分流管道对比的数值分析%Numerical Investigation of Comparing Annular with Linear Distribution Flow Pipeline in Chemical Laser

    Institute of Scientific and Technical Information of China (English)

    靳冬欢; 刘文广; 陈星; 陆启生; 赵伊君

    2011-01-01

    环柱型化学激光器中使用的分流管道的总管为环形弯曲管道,支管分布在内侧圆弧或外侧圆弧上,结构与线形分流管道有较大差别.应用计算流体力学方法,对上述各分流管道进行了三维的数值模拟及对比分析.结果表明,线形分流管道总管内的总压高于支管分布在外侧圆弧上的环形管道,但低于支管分布在内侧圆弧上的环形管道;无论是支管分流,抑或环形管道内的二次流现象都会使总管截面上产生径向速度,使得流体流动呈现明显的三维特征;分流管道各支管流量沿主流流动方向基本上是上升的,这与总管的总压分布趋势相反,而与总管的静压分布趋势相似;比较而言,支管分布在外侧圆弧上的环形分流管道的支管流量波动幅度最小,在均匀分配气流方面最具优势,线形分流管道居中,支管分布在内侧圆弧上的环形分流管道最差.%Distribution flow pipeline used in cylindrical chemical laser is composed of an annular general pipeline and a limited quantity of branch pipelines that are connected with the inner or outer circular arc of general pipeline. Its structure and flow field characteristics differ from thooe of linear distribution flow pipeline used in conventional chemical laser. Flow field characteristics of above-mentioned three kinds of distribution flow pipelines were analyzed contrastively based on three-dimension computational fluid dynamics methods. The numerical simulation results clemonstrate that total pressuue of general pipeline in linear distribution flow pipeline is higher than that in outer-circular-arc annular pipeline, but lower than that in inner-circular-arc annular pipeline. Both distribution flows of branch pipelines and secondary flows produced in annular general pipeline can excite radial velocity on the section plane of general pipeline. These phenomena enable the ges flow of general pipeline to have remarkable three

  7. Laminar forced convection slip-flow in a micro-annulus between two concentric cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Avci, Mete; Aydin, Orhan [Karadeniz Technical University, Department of Mechanical Engineering, 61080 Trabzon (Turkey)

    2008-07-01

    Forced convection heat transfer in hydrodynamically and thermally fully developed flows of viscous dissipating gases in annular microducts between two concentric micro cylinders is analyzed analytically. The viscous dissipation effect, the velocity slip and the temperature jump at the wall are taken into consideration. Two different cases of the thermal boundary conditions are considered: uniform heat flux at the outer wall and adiabatic inner wall (Case A) and uniform heat flux at the inner wall and adiabatic outer wall (Case B). Solutions for the velocity and temperature distributions and the Nusselt number are obtained for different values of the aspect ratio, the Knudsen number and the Brinkman number. The analytical results obtained are compared with those available in the literature and an excellent agreement is observed. (author)

  8. Optimum annular focusing by a phase plate

    CERN Document Server

    Arrizón, Victor; Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel

    2015-01-01

    Conventional light focusing, i. e. concentration of an extended optical field within a small area around a point, is a frequently used process in Optics. An important extension to conventional focusing is the generation of the annular focal field of an optical beam. We discuss a simple optical setup that achieves this kind of focusing employing a phase plate as unique optical component. We first establish the class of beams that being transmitted through the phase plate can be focused into an annular field with topological charge of arbitrary integer order q. Then, for each beam in this class we determine the plate transmittance that generates the focal field with the maximum possible peak intensity. In particular, we discuss and implement experimentally the optimum annular focusing of a Gaussian beam. The attributes of optimum annular focal fields, namely the high peak intensity, intensity gradient and narrow annular section, are advantageous for different applications of such structured fields.

  9. Concentrated flow erosion processes under planned fire

    Science.gov (United States)

    Langhans, Christoph; Noske, Phil; Van Der Sant, Rene; Lane, Patrick; Sheridan, Gary

    2016-04-01

    The role of wildfire in accelerating erosion rates for a certain period after fire has been well documented. Much less information is available on the erosion rates and processes after planned fires that typically burn at much lower intensity. Observational evidence, and some studies in southern and southeastern Australia suggest that erosion after planned fire can be significant if rainfall intensities exceed critical intensities and durations. Understanding erosion processes and rates under these event conditions is of critical importance for planning of burn locations away from critical human assets such as water supplies and infrastructure. We conducted concentrated flow experiments with the purpose to understand what critical conditions are required for significant erosion to occur on planned burn hillslopes. Concentrated flow runon was applied on pre-wetted, unbounded plots of 10 m at rates of 0.5, 1, 1.5 and 2 L/s, with three replicates for each rates applied at 1m distance of each other. The experiments were carried out at three sites within one burn perimeter with different burn severities ranging from low to high, with two replicates at each site. Runon was applied until an apparent steady state in runoff was reached at the lower plot boundary, which was typically between 0.7 and 2.5 minutes. The experiments were filmed and erosion depth was measured by survey methods at 1m intervals. Soil surface properties, including potential sediment trapping objects were measured and surveyed near the plots. We found that fire severity increased plot scale average erosion depth significantly even as experiments were typically much shorter on the high severity plots. Unit stream power was a good predictor for average erosion depth. Uncontrolled for variations in soil surface properties explained process behaviour: finer, ash rich surface material was much less likely to be trapped by fallen, charred branches and litter than coarser, ash-depleted material. Furthermore

  10. Study on Mechanism of Drag Reduction by Core-annular Flow in Transportation of Emulsion Matrix%乳胶基质水环输送的机理研究

    Institute of Scientific and Technical Information of China (English)

    杨佳; 刘寿康

    2012-01-01

    对目前广泛应用于乳化炸药混装车上的水环输送乳胶基质的减阻机理进行了理论分析,分别推导出层流同心水环、湍流同心水环的速度分布与流量计算公式,并得到了从层流到湍流的转捩判据.此外,优化了水环润滑装置结构参数,提出了稳定水环输送的相关措施.%The mechanism of drag reduction by core-annular flow in transportation of emulsion matrix was widely used in the existing mixing-loading truck for emulsion explosive. After theoretical analysis, formulas were deduced respectively to calculate the velocity distribution, flow rate of annular water flow in laminar and turbulent flows. The criterion of transition from laminar flow to turbulent flow was obtained. Furthermore, the optimized parameters and some stabilizing measures are also proposed for core-annular flow device.

  11. Behaviour of steel pipe exposed to fouling by heavy oil during core-annular flow; Comportamento de tubo de aco exposto a sujeira de oleo pesado durante escoamento nucleo-anular

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Adriana; Bannwart, Antonio C. [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia de Petroleo

    2004-07-01

    The use of water-assisted technologies such as core-annular flow to the pipelines of viscous oils has been proposed as an attractive alternative for production and transportation of heavy crudes in both onshore and offshore scenarios. Usually, core-annular flow can be created by injecting a relatively small water flow rate laterally in the pipe, so as to form a thin water annulus surrounding the viscous oil, which is pumped through the center. The reduction in friction losses obtained thanks to lubrication by water is significant, since the pressure drop in a steady state core flow becomes comparable to water flow only. For a complete assessment of core flow technology, however, unwanted effects associated with possible oil adhesion onto the pipe wall should be investigated, since these may cause severe fouling of the wall and pressure drop increase. It has been observed that oil adhesion on metallic surfaces may occur for certain types of crude and oilphilic pipe materials. In this work we present results of pressure drop monitoring during 35 hour-operation of a heavy oil-water core annular flow in a 26.08 mm. i.d. horizontal steel pipe. The oil used is described in terms of its main components and the results of static wet ability tests are also presented for comparison (author)

  12. Study on the annular leakage-flow-induced vibrations. 1st Report. Stability for translational and rotational single-degree-of-freedom systems; Kanjo sukimaryu reiki shindo ni kansuru kenkyu. 1. Heishin oyobi kaiten 1 jiyudokei no anteise

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.W. [Hitachi, Ltd., Tokyo (Japan); Kaneko, S. [The University of Tokyo, Tokyo (Japan); Hayama, S. [Toyama Prefectural University, Toyama (Japan)

    1999-07-25

    This study reports the stability of annular leakage-flow-induced vibrations. The pressure distribution of fluid between a fixed outer cylinder and a vibrating inner cylinder was obtained in the case of a translationally and rotationally coupled motion of the inner cylinder. The unsteady fluid force acting on the inner cylinder in the case of translational and rotational single-degree-of-freedom vibrations was then expressed in terms proportional to the acceleration, velocity, and displacement. Then the critical flow rate (at which stability was lost) was determined for an annular leakage-flow-induced vibration. Finally, the stability was investigated theoretically. It is known that instability will occur in the case of a divergent passage, but the critical flow rate depends on the passage increment in a limited range: the eccentricity of the passage and the pressure loss factor at the inlet of the passage lower the stability. (author)

  13. Effect of Annular Slit Geometry on Characteristics of Spiral Jet

    Institute of Scientific and Technical Information of China (English)

    Shigeru Matsuo; Kwon-Hee Lee; Shinsuke Oda; Toshiaki Setoguchi; Heuy-Dong Kim

    2003-01-01

    A spiral flow using an annular slit connected to a conical cylinder does not need special device to generate a tangential velocity component of the flow and differs from swirling flows. Pressurized fluid is supplied to an annular chamber and injected into the convergent nozzle through the annular slit. The annular jet develops into the spiral flow. In the present study, a spiral jet discharged out of nozzle exit was obtained by using a convergent nozzle and an annular slit set in nozzle inlet, and the effect of annular slit geometry on characteristics of the spiral jet was investigated by using a Laser Doppler Velocimeter (LDV) experimentally. Furthermore, velocity distributions of the spiral jet were compared with those of a normal jet.

  14. Numerical modelling of the flow in the annular multi-recess hydrostatic thrust bearing using CFD methods

    Directory of Open Access Journals (Sweden)

    Drbáková S.

    2013-04-01

    Full Text Available The current research of hydrostatic bearings and hydrostatic slide-ways is far from being over. The topic is constantly evolving, creating new geometries of the sliding bearings, developing new types of friction materials and lubricants. The control elements of hydraulic mechanisms that serve to regulation of the hydrostatic bearings tipping are still in progress. Almost every application has different requirements for the bearings, whether in terms of loading capacity, speed rotation, and also the price. All these aspects should be included in the design of hydrostatic thrust bearings. Thanks to great advances in the development of computer technology and software for numerical modelling, we can simulate real movement of viscous fluids. To create a numerical model of hydrostatic thrust bearing, Ansys Fluent 14.0 software package has been applied. The article describes the basic methods of numerical modelling of the given problem and evaluates the pressure field and the loading capacity of annular multi-recess hydrostatic thrust bearing and its dependence on the change in static pressure.

  15. CONCENTRATION AND VELOCITY OF DEBRIS FLOWS

    Institute of Scientific and Technical Information of China (English)

    Xiangjun FEI; Peng CUI; Yong LI

    2002-01-01

    Debris flows in nature generally fall into three groups distinct in their grain composition: water-stone flow,or sub-viscous debris flow,dominated by coarse grains; muddy flow,dominated by fine grains;and viscous debris flow composed of grains in large range. Liquid-phase velocity and sedimentary delivery resistance of sub-viscous debris flow have been discussed based on the composition characters of sub-and high-viscous debris flows. It is revealed that the presence of fine grains plays a vital role in affecting resistance and average velocity,particularly when the volume fraction of grains in the flow is relatively high,i.e. Sv > 0.45. Grain-size distribution of viscous debris flow is characterized by a bimodal curve,which explains the properties like high density and low resistance gradient of debris flows. A calculation formula is finally put forward,which has to some extent overcome locality limits and achieved a good agreement with the field observations of debris flows in Southwest China.

  16. Flow of viscoplastic fluids in a rotating concentric annulus

    DEFF Research Database (Denmark)

    Hassager, Ole; Bittleston, Simon H.

    1992-01-01

    A difficulty in any flow calculation with viscoplastic fluids such as Bingham fluids is the determination of possible plug zones in which no deformation occurs. This paper investigates the flow in a concentric annulus when there is both an axial and tangential flow, the tangent flow arising from ...

  17. Research Advances on flow field of annular centrifugal extraction%环隙式离心萃取器流场研究进展

    Institute of Scientific and Technical Information of China (English)

    潘九海; 甘仁武; 张艳红; 白志山

    2012-01-01

    围绕工业应用,人们在环隙流场稳定性、水力学特性等方面做了大量研究,而对环隙的流场流动机理、泰勒涡流场结构等方面的研究较少,随着线性和非线性理论、计算流体力学和流动可视化技术的飞速发展,对环隙流场流动机理、涡流场的结构进行详细直观描述有了可能,主要从环隙流场可视化、环隙流场数值模拟2个方面对该研究进行了系统的分析总结,并为将来的研究工作提出了几点意见.%Around the industrial application of annular centrifugal extractor ( ACE) , the flow instabilities, hydrodynamic characteristics and mass transfer performance of ACE has been extensively studied. But relatively scanty information is available on the detailed quantitative flow pattern and the structure of vortex. With the rapid development of linear and nonlinear theory, Computational Fluid Dynamics and flow visualization technology, more and more information was provided for the research of flow regime and vortex cell- The published literature has been critically analysed and presented in this paper,some specific recommendations have been made for future work.

  18. Calculation of the debris flow concentration based on clay content

    Institute of Scientific and Technical Information of China (English)

    CHEN Ningsheng; CUI Peng; LIU Zhonggang; WEI Fangqiang

    2003-01-01

    The debris flow clay content has very tremendous influence on its concentration (γC). It is reported that the concentration can be calculated by applying the relative polynomial based on the clay content. Here one polynomial model and one logarithm model to calculate the concentration based on the clay content for both the ordinary debris flow and viscous debris flow are obtained. The result derives from the statistics and analysis of the relationship between the debris flow concentrations and clay content in 45 debris flow sites located in the southwest of China. The models can be applied for the concentration calculation to those debris flows that are impossible to observe. The models are available to calculate the debris flow concentration, the principles of which are in the clay content affecting on the debris flow formation, movement and suspending particle diameter. The mechanism of the relationship of the clay content and concentration is clear and reliable. The debris flow is usually of micro-viscous when the clay content is low (<3%), by analyzing the developing tendency on the basics of the relationship between the clay content and debris flow concentration. Indeed, the less the clay content, the less the concentration for most debris flows. The debris flow tends to become the water rock flow or the hyperconcentrated flow with the clay content decrease. Through statistics it is apt to transform the soil into the viscous debris flow when the clay content of ranges is in 3%-18%. Its concentration increases with the increasing of the clay content when the clay content is between 5% and 10%. But the value decreases with the increasing of the clay content when the clay content is between 10% and 18%. It is apt to transform the soil into the mudflow, when the clay content exceeds 18%. The concentration of the mudflow usually decreases with the increase of the clay content, and this developing tendency reverses to that of the micro-viscous debris flow. There is

  19. Field methods for measuring concentrated flow erosion

    Science.gov (United States)

    Castillo, C.; Pérez, R.; James, M. R.; Quinton, J. N.; Taguas, E. V.; Gómez, J. A.

    2012-04-01

    techniques (3D) for measuring erosion from concentrated flow (pole, laser profilemeter, photo-reconstruction and terrestrial LiDAR) The comparison between two- and three-dimensional methods has showed the superiority of the 3D techniques for obtaining accurate cross sectional data. The results from commonly-used 2D methods can be subject to systematic errors in areal cross section that exceed magnitudes of 10 % on average. In particular, the pole simplified method has showed a clear tendency to understimate areas. Laser profilemeter results show that further research on calibrating optical devices for a variety of soil conditions must be carried out to improve its performance. For volume estimations, photo-reconstruction results provided an excellent approximation to terrestrial laser data and demonstrate that this new remote sensing technique has a promising application field in soil erosion studies. 2D approaches involved important errors even over short measurement distances. However, as well as accuracy, the cost and time requirements of a technique must be considered.

  20. Subcutaneous granuloma annulare

    Directory of Open Access Journals (Sweden)

    Dhar Sandipan

    1994-01-01

    Full Text Available Two cases of subcutaneos granuloma annulare are reported. Clinical presentation was in the form of hard subcutaneous nodules; histopathology confirmed the clinical diagnosis. The cases were unique because of onset in adult hood, occurrence over unusual sites and absence of classical lesions of granuloma annulare elsewhere.

  1. Subcutaneous granuloma annulare

    Directory of Open Access Journals (Sweden)

    Dhar Sandipan

    1993-01-01

    Full Text Available Two cases of subcutaneous granuloma annulare are reported. Clinical presentation was in the form of hard subcutaneous nodules, histopathology confirmed the clinical diagnosis. The cases were unique because of onset in adult age, occurrence over unusual sites and absence of classical lesions of granuloma annulare elsewhere.

  2. Three-dimensional investigation of liquid film structure at the initial area of annular-dispersed flow

    Directory of Open Access Journals (Sweden)

    Alekseenko Sergey

    2016-01-01

    Full Text Available Initial stage of downward flow of gas-sheared liquid film in a vertical rectangular duct was studied using brightness-based laser-induced fluorescence technique. Measurements were resolved along both longitudinal and transverse coordinates and time. The initial high-frequency waves which are formed at the inlet were found to be two-dimensional. These waves are promptly broken into localised horseshoe-shaped waves which merge downstream to form large-scale quasi-2D disturbance waves. Peculiarities of three-dimensional evolution of waves of different types were studied in a wide range of flow parameters.

  3. LAMINAR FLOW AND HEAT TRANSFER IN MICRO-ANNULAR CHANNEL IN SLIP FLOW REGIME%滑移流区内微环缝槽道中的层流流动与换热

    Institute of Scientific and Technical Information of China (English)

    朱恂; 辛明道

    2001-01-01

    In this article, the momentum and energy equations with the boundary conditions of slip velocity and temperature jump are solved for the hydraulic and thermalfully developed laminar flow of the incompressible fluid in micro-annular channel. A theoretical analysis is conducted for flow and heat transfer characteristics in this micro channel on the condition of one wall heated alonewith uniform heat flux and two walls heated with different heat flux in slipflow regime. The influences of the Kn number, the ratio of inner diameter toouter diameter and the heat flux ratio on the flow and heat transfercharacteristics are discussed, respectively. The results show that the frictioncoefficient and Nusselt number in the micro-annular channel are smaller thanthat in the macrochannel, and decrease with the increase of Kn number.%本文针对微环缝槽道采用速度滑移和温度跳跃边界条件求解了不可压缩气体的N-S方程和能量方程,理论分析了微环缝槽道在单侧或双侧不同热流密度加热条件下的流动与层流换热特性,讨论了Kn数、内外径比对流动阻力及换热特性的影响。结果表明:滑移流区微环缝通道内的流阻和Nusselt数明显低于连续流区;且随着Kn数的增加,流阻和Nusselt数均减小;但其随内外径比r*的变化趋势与连续流区相似。

  4. Experiment on the Effect of Sediment Concentration on Flow Structure

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The paper studies on the sediment-laden flow by using MicroADV.Laboratory calibration has been conducted to determine the relationship between backscattered signal strength and sediment concentration. Based on the experimental data,the interactions between sediment and fluid in open channel flow are investi- gated.The experiment shows that there exist inner relation between sediment concentration and turbulence, and the relationship is distinctry related to the diameter of particle as well as the flow co...

  5. Dispersion phenomena in helical flow in a concentric annulus.

    Science.gov (United States)

    Song, Young Seok; Brenner, Howard

    2009-12-14

    We examined dispersion phenomena of solutes in helical flow in a concentric annulus through a multiscale approach. The helical flow was developed by the combination of the Poiseuille flow and Couette flow. Here, we present an analytic model that can address the multidimensional Taylor dispersion in the helical flow under a lateral field of thermophoresis (or thermal diffusion) in the gapwise direction. Macroscopic parameters including the average solute velocity and dispersivity were analyzed using relevant microscopic physicochemical properties. The mathematically obtained results were validated by the numerical simulation carried out in this study. The findings show that macrotransport processes are robust and straightforward to handle multidimensional dispersion phenomena of solutes in helical flow. This study is expected to provide a theoretical platform for applications of helical flow such as tube exchangers, oil drilling, and multidimensional field flow fractionations (e.g., helical flow field flow fractionation).

  6. Coupling Navier-stokes and Cahn-hilliard Equations in a Two-dimensional Annular flow Configuration

    KAUST Repository

    Vignal, Philippe

    2015-06-01

    In this work, we present a novel isogeometric analysis discretization for the Navier-Stokes- Cahn-Hilliard equation, which uses divergence-conforming spaces. Basis functions generated with this method can have higher-order continuity, and allow to directly discretize the higher- order operators present in the equation. The discretization is implemented in PetIGA-MF, a high-performance framework for discrete differential forms. We present solutions in a two- dimensional annulus, and model spinodal decomposition under shear flow.

  7. Instability of Taylor-Couette Flow between Concentric Rotating Cylinders

    CERN Document Server

    Dou, H S; Phan-Thien, N; Yeo, K S; Dou, Hua-Shu; Khoo, Boo Cheong; Phan-Thien, Nhan; Yeo, Koon Seng

    2005-01-01

    The energy gradient theory is used to study the instability of Taylor-Couette flow between concentric rotating cylinders. In our previous studies, the energy gradient theory was demonstrated to be applicable for wall bounded parallel flows. It was found that the critical value of the energy gradient parameter K at subcritical transition is about 370-389 for wall bounded parallel flows (which include plane Poiseuille flow, pipe Poiseuille flow and plane Couette flow) below which no turbulence occurs. In this paper, the detailed derivation for the calculation of the energy gradient parameter in the flow between concentric rotating cylinders is provided. The theoretical results for the critical condition of primary instability obtained are in very good agreement with the experiments found in literature. The mechanism of spiral vortices generation for counter-rotating of two cylinders is also explained using the energy gradient theory. The energy gradient theory can also serve to relate the condition of flow tran...

  8. Eosinophilic annular erythema.

    Science.gov (United States)

    Sempau, Leticia; Larralde, Margarita; Luna, Paula Carolina; Casas, Jose; Staiger, Hernan

    2012-03-15

    Eosinophilic annular erythema is a rare benign recurrent disease, originally described in children, characterized by the recurrent appearance of persistent non-pruritic, urticarial annular lesions. Histologically a perivascular infiltrate composed of lymphocytes and abundant eosinophils in the dermis is exhibited. We report the case of a 15-year-old boy who presented with a 4-year history of recurrent flares of erythematous annular plaques on the trunk and extremities. The lesions resolved spontaneously after 3-5 weeks with no accompanying signs. A biopsy showed a mainly perivascular lymphocytic infiltrate with numerous eosinophils in the dermis.

  9. 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)

  10. EXPERIMENTAL STUDY ON EQUILIBRIUM CONCENTRATION OF DEBRIS FLOWS

    Institute of Scientific and Technical Information of China (English)

    Bin YU

    2001-01-01

    The paper presents experimental study of debris flows. The equilibrium concentration of solid particle in the flow is a function of the energy slope, density of solid particle and kinetic friction angle of particles. The kinetic friction angle is a function of internal friction angle, the concentration of solid particles and the maximum possible concentration. To determine the function between the kinetic friction angle and internal friction angle is the aim of this research. Flume experiments of equilibrium concentration about particles in water and slurry were conducted. The large density slurry made the coarse particles be able to move in small slope. The function between the kinetic friction angle and internal friction angle was found from these experiments. The coarse particles and fine particles are well mixed. D50 demarcation line was suggested in this paper to demarcate the coarse particle and fine particle of debris flows. The equilibrium concentration of debris flows was calculated by using Ds0 demarcation for the debris flows in field. The equilibrium concentration of debris flows calculated by the function between the kinetic friction angle and internal friction angle was close to the equilibrium concentration data of debris flows in field.

  11. Phosphorus concentration changes in hydrological flows and pathways

    Science.gov (United States)

    Mellander, Per-Erik; Jordan, Phil

    2017-04-01

    To reach goals of sustainable food production, targeted schemes designed to attenuate pollution from agricultural sources to water are needed. Such approaches require insight into temporal and spatial variability in the most representative flows and active pollution transfer pathways. Interpreting changes in total stream flow may be misleading since some changes may only be apparent in specific flows or pathways. In this study we present concentrations of reactive phosphorus (RP) in apportioned flows and pathways in four small (ca. 10 km2) intensively managed, Irish agricultural river catchments with different land use (arable and grassland) and soil permeability (poorly drained and well drained). Seven years of sub-hourly stream water RP concentration and discharge were analysed for RP concentrations in different flow percentiles (high, intermediate and low flow) and in apportioned transfer pathways (quick flow, interflow and slowflow) estimated from hydrograph and loadograph separation techniques. The results were viewed in the light of catchment hydrological flashiness (Q10:Q90), management and the influences of short-term changes in weather. There were intra-annual and interannual changes in the apportioned monthly and seasonal RP concentrations and some of these changes did not fully correspond to changes in RP concentrations in total stream flow. Even if monthly average RP concentrations were highest in summer quick flow (QF) pathways (e.g. Arable A: QF = 0.184 mg/l in July) the low flow conditions produced higher stream RP concentrations than the high flows in the arable catchments (e.g. Arable A: 0.044 mg/l compared to 0.029 mg/l). Two catchments responded positively to current mitigation measures with a successively reduced RP concentration in QF pathways between the winters (e.g. Grassland A: 0.275mg/l to 0.085 mg/l). However, in that catchment and the other grassland catchment the low flow RP concentrations consistently increased relative to similar low

  12. Annular pancreas (image)

    Science.gov (United States)

    Annular pancreas is an abnormal ring or collar of pancreatic tissue that encircles the duodenum (the part of the ... intestine that connects to stomach). This portion of pancreas can constrict the duodenum and block or impair ...

  13. Caída de presión de un flujo turbulento en un espacio anular con hélices insertadas//The pressure drop of turbulent flow in an annular space with wire coil inserts

    Directory of Open Access Journals (Sweden)

    Josué Imbert González

    2015-05-01

    Full Text Available El trabajo presentado evaluó el comportamiento experimental de la caída de presión en un espacio anular con alambres enrollados insertados para números de Reynolds entre 1500 y 5000. La zona de prueba se seleccionó alejada de la influencia de los efectos de entrada. Anteriormente se realizaron pruebas de visualización del flujo para verificar la presencia de un flujo turbulento en esta gama del número de Reynolds. A partir de los datos experimentales se obtuvieron ecuaciones de correlación del factor de fricción para el flujo turbulento. Las ecuaciones obtenidas se compararon con los datos experimentales. Los resultados indican hasta qué punto las hélices inducen la aparición de turbulencias en un espacio anularPalabras claves: caída de presión, flujo anular, análisis hidrodinámico, visualización de flujo, hélices insertadas.______________________________________________________________________________AbstractThe work presented evaluates the experimental behavior of the pressure drop in an annular space with coiled wires inserted forReynolds numbers between 1500 and 5000. The test zone was selected away from the influence of entrance effects. Previously flow visualization tests were performed to verify the presence of a turbulent flow in this range of Reynolds number. From the experimental data were obtained correlation equations of the friction factor for turbulent flow. The equations obtained were compared with experimental data. The results indicate to what extent the helices induce the occurrence of turbulence in an annular space.Key words: drop pressure, annular flow, hydrodynamic analysis, visualization flow, wire coil inserts.

  14. CFD Simulation of Annular Centrifugal Extractors

    Directory of Open Access Journals (Sweden)

    S. Vedantam

    2012-01-01

    Full Text Available Annular centrifugal extractors (ACE, also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.

  15. Local interfacial area concentration measurement in bubbly flow

    Science.gov (United States)

    Ishii, M.; Revankar, S. T.

    1990-10-01

    The interfacial area concentration is one of the most important parameters in a thermal-hydraulic analysis of two-phase flow systems based on the two-fluid model. A theoretical foundation of the measurement method for the time averaged local interfacial area using a double sensor probe is presented. Based on this theory, the double sensor resistivity probe was employed for the measurement of local properties of two-phase flow such as the interfacial velocity, local interfacial area concentration and void fraction in vertical air-water bubbly flow. Experimental data are presented on the radial profiles of the void fraction, bubble velocity, bubble chord length and interfacial area concentration at various gas flow rates. In addition to these, some statistical information on turbulent motions of bubbles are presented. Each of the double sensors are checked against the global void measurement using a differential pressure. The result is very satisfactory. Furthermore, the area averaged void fraction, and the interfacial area concentration obtained from the double sensor probe measurement compared very well with the photographic measurements. The results show that the double sensor probe method is accurate and reliable for the local measurements of interfacial area and void fraction in bubbly two-phase flow. Results of the measurement of interfacial area concentration with the double sensor probe in forced flow loop are presented for bubbly flow at different liquid flow rates. The data indicate that the radial profiles of the interfacial area concentration show similar dependence on the liquid and gas flow rate like radial profiles of void fraction in the bubbly flow regime.

  16. Relation between the occurrence of Burnout and differential pressure fluctuation characteristics caused by the disturbance waves passing by a flow obstacle in a vertical boiling two-phase upward flow in a narrow annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Shoji [Yokohama National University, Yokohama 240-8501 (Japan)]. E-mail: morisho@ynu.ac.jp; Fukano, Tohru [Kurume Institute of University, Fukuoka 830-0052 (Japan)]. E-mail: fukanot@cc.kurume-it.ac.jp

    2006-05-15

    If a flow obstacle such as a spacer is placed in a boiling two-phase flow within a channel, the temperature on the surface of the heating tube is severely affected by the existence of the spacer. Under certain conditions the spacer has a cooling effect, and under other conditions the spacer causes dryout of the cooling water film on the heating surface, resulting in burnout of the tube. The burnout mechanism near the spacer, however, remains unclear. In a previous paper (Fukano, T., Mori, S., Akamatsu, S., Baba, A., 2002. Relation between temperature fluctuation of a heating surface and generation of drypatch caused by a cylindrical spacer in a vertical boiling two-phase upward flow in a narrow annular channel. Nucl. Eng. Des. 217, 81-90), we reported that the disturbance wave has a significant effect on dryout occurrence. Therefore, in the present paper, the relation between dryout, burnout occurrence, and interval between two successive disturbance waves obtained from the differential pressure fluctuation caused by the disturbance waves passing by a spacer, is further discussed in detail.

  17. Behavior of an heterogeneous annular FBR core during an unprotected loss of flow accident: Analysis of the primary phase with SAS-SFR

    Energy Technology Data Exchange (ETDEWEB)

    Massara, S.; Schmitt, D.; Bretault, A.; Lemasson, D.; Darmet, G.; Verwaerde, D. [EDF R and D, 1, Avenue du General de Gaulle, 92141 Clamart (France); Struwe, D.; Pfrang, W.; Ponomarev, A. [Karlsruher Institut fuer Technologie KIT, Institut fuer Neutronenphysik und Reaktortechnik INR, Hermann-von-Helmholtz-Platz 1, Gebaude 521, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-07-01

    In the framework of a substantial improvement on FBR core safety connected to the development of a new Gen IV reactor type, heterogeneous core with innovative features are being carefully analyzed in France since 2009. At EDF R and D, the main goal is to understand whether a strong reduction of the Na-void worth - possibly attempting a negative value - allows a significant improvement of the core behavior during an unprotected loss of flow accident. Also, the physical behavior of such a core is of interest, before and beyond the (possible) onset of Na boiling. Hence, a cutting-edge heterogeneous design, featuring an annular shape, a Na-plena with a B{sub 4}C plate and a stepwise modulation of fissile core heights, was developed at EDF by means of the SDDS methodology, with a total Na-void worth of -1 $. The behavior of such a core during the primary phase of a severe accident, initiated by an unprotected loss of flow, is analyzed by means of the SAS-SFR code. This study is carried-out at KIT and EDF, in the framework of a scientific collaboration on innovative FBR severe accident analyses. The results show that the reduction of the Na-void worth is very effective, but is not sufficient alone to avoid Na-boiling and, hence, to prevent the core from entering into the primary phase of a severe accident. Nevertheless, the grace time up to boiling onset is greatly enhanced in comparison to a more traditional homogeneous core design, and only an extremely low fraction of the fuel (<0.1%) enters into melting at the end of this phase. A sensitivity analysis shows that, due to the inherent neutronic characteristics of such a core, the gagging scheme plays a major role on the core behavior: indeed, an improved 4-zones gagging scheme, associated with an enhanced control rod drive line expansion feed-back effect, finally prevents the core from entering into sodium boiling. This major conclusion highlights both the progress already accomplished and the need for more detailed

  18. Flow of viscoplastic fluids in a rotating concentric annulus

    DEFF Research Database (Denmark)

    Hassager, Ole; Bittleston, Simon H.

    1992-01-01

    pressure gradient is small compared to the yield stress of the fluid then the full solution predicts the existence of plugs attached to the outer wall of the annulus. The slot approximation fails to predict this feature. For larger pressure gradients the two solutions are in good agreement. The analytical......A difficulty in any flow calculation with viscoplastic fluids such as Bingham fluids is the determination of possible plug zones in which no deformation occurs. This paper investigates the flow in a concentric annulus when there is both an axial and tangential flow, the tangent flow arising from...... rotation of the inner cylinder of the annulus. The flow is analyzed by considering flow in a slot, for which an analytical solution is given, and by solving the full problem numerically. It is shown that when the boundary is set in motion an applied pressure gradient will always cause flow. If the applied...

  19. Annular Pressure Seals and Hydrostatic Bearings

    Science.gov (United States)

    2006-11-01

    affecting the rotordynamics of liquid turbopumps, in particular those handling large density fluids. Highlights on the bulk-flow analysis of annular seals... rotordynamic stability. Hydrostatic bearings rely on external fluid pressurization to generate load support and large centering stiffnesses, even in...SEALS IN PUMP APPLICATIONS Seal rotordynamic characteristic have a primary influence on the stability response of high-performance turbomachinery [1

  20. Interfacial area concentration in steady fully-developed bubbly flow

    Energy Technology Data Exchange (ETDEWEB)

    Hibiki, T. [Kyoto Univ., Research Reactor Institute (Japan); Ishii, M. [Purdue Univ., Lafayette, IN (United States). School of Nuclear Engineering

    2001-07-01

    A simple equation for the interfacial area concentration under steady fully-developed bubbly flow condition has been derived from the interfacial area transport equation. The derived theoretical equation has been modified to obtain experimentally supported predictive correlation. The obtained interfacial area correlation was validated by 204 data sets measured in air-water bubbly flows under various conditions. These data sets covered extensive flow and loop conditions such as channel geometry (circular or rectangular channel), flow direction (vertical or horizontal flow), superficial gas velocity (0,018 m/s - 4,87 m/s), superficial liquid velocity (0,262 m/s - 6,55 m/s) and interfacial area concentration (25,8 m{sup -1} - 1083 m{sup -1} ). An excellent agreement was obtained between the developed semi-theoretical correlation and data within an average relative deviation of 11,1 %. (author)

  1. Characteristics of the entrained droplets in gas-liquid two-phase annular flow%气液两相环状流中夹带液滴特性研究

    Institute of Scientific and Technical Information of China (English)

    樊文娟; 彭颖

    2016-01-01

    气液两相环状流中液体薄膜沿着管壁流动而速度较大的气核在管中心流动,通常速度较大的气核会夹带部分液滴。液滴夹带来源于沿着管壁流动的液体层的雾化速率和液滴沉积速率之间的平衡过程。目前大多数环状两相流的研究主要集中在对主要夹带现象的分析上。文中主要从夹带液滴直径、液滴速度分布和夹带分数3个方面进行夹带液滴特性研究。%The liquid film flows along the pipe wall and the gas nucleus of higher speed flows in the center of the pipe flow in the gas-liquid two-phase annular flow,usually the high speed gas nucleus entrains some droplets. The droplet entrainment is derived from a balance between the rate of atomization of the liquid layer flowing along the pipe wall and the rate of deposition of droplets. When gas flow rate is low,gravity sedimentation controls the deposition rate,and when the gas phase is at high flow velocity,droplet turbulence controls the deposition rate. At present,most of the annular two-phase flow research focuses on the analysis of the main entrainment phenomenon. This article mainly discussed the entrained droplets from the gas liquid interface,because the entrained droplets play an important role in a lot of flow parameters. Therefore, this article made the droplet entrainment characteristics research mainly from the three aspects,namely droplet diameter, droplet velocity distribution and entrainment fraction.

  2. Applying CFD in the analysis of heavy oil - water two-phase flow in joints by using core annular flow technique

    Directory of Open Access Journals (Sweden)

    T Andrade

    2016-09-01

    Full Text Available In the oil industry the multiphase flow occur throughout the production chain, from reservoir rock until separation units through the production column, risers and pipelines. During the whole process the fluid flows through the horizontal pipes, curves, connections and T joints. Today, technological and economic challenges facing the oil industry is related to heavy oil transportation due to its unfavourable characteristics such as high viscosity and high density that provokes high pressure drop along the flow. The coreflow technique consists in the injection of small amounts of water into the pipe to form a ring of water between the oil and the wall of the pipe which provides the reduction of friction pressure drop along the flow. This paper aim to model and simulate the transient two-phase flow (water-heavy oil in a horizontal pipe and T joint by numerical simulation using the software ANSYS CFX® Release 12.0. Results of pressure and volumetric fraction distribution inside the horizontal pipe and T joint are presented and analysed.

  3. Axisymmetric instability of the Poiseuille-Couette flow between concentric cylinders at high Reynolds numbers

    Science.gov (United States)

    Savenkov, I. V.

    2015-02-01

    For the pressure-driven flow in an annular channel with a wall moving in the axial direction, its linear instability with respect to axisymmetric perturbations at high Reynolds numbers is investigated within the framework of the triple-deck theory. When the gap between the cylinders is sufficiently small (as compared to the radii of the cylinders), it is shown that the perturbations can split into two wave packets, the first of which grows faster and moves at a higher velocity.

  4. Axial Creeping Flow in the Gap between a Rigid Cylinder and a Concentric Elastic Tube

    CERN Document Server

    Elbaz, Shai B

    2015-01-01

    We examine transient axial creeping flow in the annular gap between a rigid cylinder and a concentric elastic tube. The gap is initially filled with a thin fluid layer. The study focuses on viscous-elastic time-scales for which the rate of solid deformation is of the same order-of-magnitude as the velocity of the fluid. We employ an elastic shell model and the lubrication approximation to obtain a forced nonlinear diffusion equation governing the viscous-elastic interaction. In the case of an advancing liquid front into a configuration with a negligible film layer (compared with the radial deformation of the elastic tube), the governing equation degenerates into a forced porous medium equation, for which several closed-form solutions are presented. In the case where the initial film layer is non-negligible, self-similarity is used to devise propagation laws for a pressure driven liquid front. When advancing external forces are applied on the tube, the formation of dipole structures is shown to dominate the in...

  5. Two-Fluid Couette Flow between Concentric Cylinders.

    Science.gov (United States)

    1984-01-01

    CONCENTRIC CYLINDERS Yuriko Renardy and Daniel D. Joseph* Technical Summary Report #2622 January 1984 ABSTRACT -1W considers,he flow of two immiscible...CYLINDERS Yuriko Renardy and Daniel D. Joseph* Introduction We consider linear stability of the flow of two immiscible fluids separated by an interface...AUTiOR(,) 8. CONTRACT OR GRANT NUMBER(@) Yuriko Renardy and Daniel D. Joseph DAAGZ9-80-C-0041 11. PERFORMING ORGANIZATION NAME AND ADDRESS 10

  6. Stability characteristics of hyper-concentration flow in open channel

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The flow instability is related to many engineering problems and belongs to a wide-ranging research field. When the problem on the transition from the laminar to the turbulence caused by the instability of the laminar is studied,the "neutral line" and the critical Reynolds number are always taken as the criterion to judge whether a certain kind of flow is stable,whose corresponding flow medium is the clear water,that is,the single-phase Newtonian fluid. And it is not studied in the traditional in-stability theory that the hyper-concentration flow widely exists in rivers. This shortage can be covered by this research. Study shows that the instability of non-Newtonian fluid such as hyper-concentration fluid,compared with Newtonian fluid such as clear water,is influenced by not only Reynolds number,the ratio of the inertia force and the viscous force,but also many other factors such as the sediment concentration,the concentration distribution,the grain size,the volu-metric weight of the sediment and so on,which make the mechanical principle even more complex. So the results of the research can supply the scientific basis for the explanations of "slurrying river",the turbulence intensity of the flow carrying sediment and the variance of the turbulence structure.

  7. Stability characteristics of hyper-concentration flow in open channel

    Institute of Scientific and Technical Information of China (English)

    XU HaiJue; BAI YuChuan

    2008-01-01

    The flow instability is related to many engineering problems and belongs to a wide-rankling research field. When the problem on the transition from the laminar to the turbulence caused by the instability of the laminar is studied, the "neutral line" and the critical Reynolds number are always taken as the criterion to judge whether a certain kind of flow is stable, whose corresponding flow medium is the clear water, that is, the single-phase Newtonian fluid. And it is not studied in the traditional in-stability theory that the hyper-concentration flow widely exists in rivers. This shortage can be covered by this research. Study shows that the instability of non-Newtonian fluid such as hyper-concentration fluid, compared with Newtonian fluid such as clear water, is influenced by not only Reynolds number, the ratio of the inertia force and the viscous force, but also many other factors such as the sediment concentration, the concentration distribution, the grain size, the volu-metric weight of the sediment and so on, which make the mechanical principle even more complex. So the results of the research can supply the scientific basis for the explanations of "slurrying river", the turbulence intensity of the flow carrying sediment and the variance of the turbulence structure.

  8. Flow in a small annulus between concentric cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Luecke, M.; Mihelcic, M.; Wingerath, K. (Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Festkoerperforschung); Pfister, G. (Kiel Univ. (Germany, F.R.). Inst. fuer Angewandte Physik)

    1984-03-01

    Rotationally symmetric vortex flows between concentric cylinders with the inner one rotating and the outer one at rest have been investigated by numerical simulation and by laser-Doppler velocimetry for an annulus of aspect ratio GAMMA = 1.05 with a radius ratio eta = 0.5066. Stationary states and relaxation towards them were explored close to the transition from the primary flow, which is mirror symmetric with respect to the midplane of the annulus, to a flow which gradually loses the symmetry. Detailed comparison of numerically simulated and measured velocity fields is made.

  9. 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.

  10. Generalized granuloma annulare

    Directory of Open Access Journals (Sweden)

    Khatri M

    1995-01-01

    Full Text Available A 35-years-old female patient had generalized pruritic papular lesions, distributed like dermatitis herpetiformis for last 4 years. Histopathologic changes were typical of granuloma annulare with negative results of direct immunofluorescence. The patient did not have association of diabetes mellitus or any other systemic disease. She failed to respond to dapsone therapy and 13-cis-retinoic acid.

  11. Ultrasonic analyte concentration and application in flow cytometry

    Energy Technology Data Exchange (ETDEWEB)

    Kaduchak, Gregory; Goddard, Greg; Salzman, Gary; Sinha, Dipen; Martin, John C.; Kwiatkowski, Christopher; Graves, Steven

    2015-07-07

    The present invention includes an apparatus and corresponding method for concentrating analytes within a fluid flowing through a tube using acoustic radiation pressure. The apparatus includes a function generator that outputs a radio frequency electrical signal to a transducer that transforms the radio frequency electric signal to an acoustic signal and couples the acoustic signal to the tube. The acoustic signal is converted within the tube to acoustic pressure that concentrates the analytes within the fluid.

  12. Ultrasonic analyte concentration and application in flow cytometry

    Energy Technology Data Exchange (ETDEWEB)

    Kaduchak, Gregory; Goddard, Greg; Salzman, Gary; Sinha, Dipen; Martin, John C.; Kwiatkowski, Christopher; Graves, Steven

    2014-07-22

    The present invention includes an apparatus and corresponding method for concentrating analytes within a fluid flowing through a tube using acoustic radiation pressure. The apparatus includes a function generator that outputs a radio frequency electrical signal to a transducer that transforms the radio frequency electric signal to an acoustic signal and couples the acoustic signal to the tube. The acoustic signal is converted within the tube to acoustic pressure that concentrates the analytes within the fluid.

  13. Ultrasonic analyte concentration and application in flow cytometry

    Science.gov (United States)

    Kaduchak, Gregory; Goddard, Greg; Salzman, Gary; Sinha, Dipen; Martin, John C.; Kwiatkowski, Christopher; Graves, Steven

    2008-03-11

    The present invention includes an apparatus and corresponding method for concentrating analytes within a fluid flowing through a tube using acoustic radiation pressure. The apparatus includes a function generator that outputs a radio frequency electrical signal to a transducer that transforms the radio frequency electric signal to an acoustic signal and couples the acoustic signal to the tube. The acoustic signal is converted within the tube to acoustic pressure that concentrates the analytes within the fluid.

  14. Erosion by shallow concentrated flow - experimental model deconstruction

    Science.gov (United States)

    Seeger, M.; Wirtz, S.; Ali, M.

    2012-04-01

    the sediment concentration. It is also shown that hydraulic parameters are not able to predict the combination of sediment detachment and transport. Moreover, the relationship between flowing water and sediment transport is shown to be complex, depending on the morphological evolution of the bed. The field experiments confirm these results, and also show that under variable conditions higher transport rates than those predicted by different model concepts are possible. Soil erosion by flowing water is much more complex than reflected in model concepts: they neither reflect the process variability nor the interaction between the different dynamic parameters of flow and soils. We conclude that mechanistic concepts, in which simple or composite predictors define the dynamics of soil erosion, can not succeed in soil erosion modelling.

  15. Magnetic flux concentration and zonal flows in magnetorotational instability turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Xue-Ning [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States); Stone, James M., E-mail: xbai@cfa.harvard.edu [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2014-11-20

    Accretion disks are likely threaded by external vertical magnetic flux, which enhances the level of turbulence via the magnetorotational instability (MRI). Using shearing-box simulations, we find that such external magnetic flux also strongly enhances the amplitude of banded radial density variations known as zonal flows. Moreover, we report that vertical magnetic flux is strongly concentrated toward low-density regions of the zonal flow. Mean vertical magnetic field can be more than doubled in low-density regions, and reduced to nearly zero in high-density regions in some cases. In ideal MHD, the scale on which magnetic flux concentrates can reach a few disk scale heights. In the non-ideal MHD regime with strong ambipolar diffusion, magnetic flux is concentrated into thin axisymmetric shells at some enhanced level, whose size is typically less than half a scale height. We show that magnetic flux concentration is closely related to the fact that the turbulent diffusivity of the MRI turbulence is anisotropic. In addition to a conventional Ohmic-like turbulent resistivity, we find that there is a correlation between the vertical velocity and horizontal magnetic field fluctuations that produces a mean electric field that acts to anti-diffuse the vertical magnetic flux. The anisotropic turbulent diffusivity has analogies to the Hall effect, and may have important implications for magnetic flux transport in accretion disks. The physical origin of magnetic flux concentration may be related to the development of channel flows followed by magnetic reconnection, which acts to decrease the mass-to-flux ratio in localized regions. The association of enhanced zonal flows with magnetic flux concentration may lead to global pressure bumps in protoplanetary disks that helps trap dust particles and facilitates planet formation.

  16. The Flow Behavior of Poly(m-Phenyleneisophthalamide) Concentrated Solution

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    By means of HAAKE RS105L cone and plate rheometer theflow behavior of poly (m-phenyleneisophthalamide ) (PMIA)concentrated solution, including viscous flow activation energy, non-Newtonian index, structural viscosity index and relaxation time of the PMIA solution were studied. The effect of concentration and temperature of the solution and molecular weight of the polymer on its non-Newtonian behavior was investigated. The results showed that PMIA concentrated solutien prepared via low temperature condensation was of non-Newtonian fluid. With the decrease of trmperature,increase of solution concentration and PMIA molecular weight, the deviation of the solution from Newtonian behavior decreased. The molecular weight of the polymer and the concentration of the solution affected the nonNewtonian behavior more intensively.

  17. Confocal Annular Josephson Tunnel Junctions

    Science.gov (United States)

    Monaco, Roberto

    2016-09-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  18. SIMULATION OF LOW-CONCENTRATION SEDIMENT-LADEN FLOW BASED ON TWO-PHASE FLOW THEORY

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Low concentration sediment-laden flow is usually involved in water conservancy, environmental protection, navigation and so on. In this article, a mathematical model for low-concentration sediment-laden flow was suggested based on the two-phase flow theory, and a solving scheme for the mathematical model in curvilinear grids was worked out. The observed data in the Zhang River in China was used for the verification of the model, and the calculated results of the water level, velocity and river bed deformation are in agreement with the observed ones.

  19. Gas flow path for a gas turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, Matthew D.; Charron, Richard C.; Snyder, Gary D.; Pankey, William W.; Mayer, Clinton A.; Hettinger, Benjamin G.

    2017-03-14

    A duct arrangement in a can annular gas turbine engine. The gas turbine engine has a gas delivery structure for delivering gases from a plurality of combustors to an annular chamber that extends circumferentially and is oriented concentric to a gas turbine engine longitudinal axis for delivering the gas flow to a first row of blades A gas flow path is formed by the duct arrangement between a respective combustor and the annular chamber for conveying gases from each combustor to the first row of turbine blades The duct arrangement includes at least one straight section having a centerline that is misaligned with a centerline of the combustor.

  20. Edge Vortex Flow Due to Inhomogeneous Ion Concentration

    Science.gov (United States)

    Sugioka, Hideyuki

    2017-04-01

    The ion distribution of an open parallel electrode system is not known even though it is often used to measure the electrical characteristics of an electrolyte. Thus, for an open electrode system, we perform a non-steady direct multiphysics simulation based on the coupled Poisson-Nernst-Planck and Stokes equations and find that inhomogeneous ion concentrations at edges cause vortex flows and suppress the anomalous increase in the ion concentration near the electrodes. A surprising aspect of our findings is that the large vortex flows at the edges approximately maintain the ion-conserving condition, and thus the ion distribution of an open electrode system can be approximated by the solution of a closed electrode system that considers the ion-conserving condition rather than the Gouy-Chapman solution, which neglects the ion-conserving condition. We believe that our findings make a significant contribution to the understanding of surface science.

  1. Flow condensation in tube filled with annular metal foam%内壁填充环状金属泡沫的管内流动凝结换热

    Institute of Scientific and Technical Information of China (English)

    徐会金; 屈治国; 杜艳平; 何雅玲; 陶文铨; 卢天健

    2011-01-01

    通过采用在圆管内壁填充环状金属泡沫的方法强化管内对流凝结换热,实验研究了制冷剂R134a在内壁填充环状金属泡沫管内的流动凝结的压降和换热,克服了完全填充金属泡沫管流动阻力大的缺点.用于计算传热系数的管壁温度通过热电偶测量得到.综合分析了质量流速和两相流体干度对流动凝结压降及传热系数的影响.研究结果表明内壁填充环状金属泡沫管压降远大于光管,压降随质量流速和干度的增加而迅速增大且呈非线性.通过壁面温度分布和温度波动对内壁填充环状金属泡沫管内的两相流型进行判别.发现影响该类强化管凝结换热的两种主要流型:分层流和环状流.内壁填充环状金属泡沫管的凝结传热系数大于光管,且随着质量流速和干度的增加传热系数增大,该类强化管流动凝结传热系数是光管的2倍左右.%The tube with internally sintered annular metal foam layer is used to enhance the flow condensation heat transfer. The pressure drop and heat transfer of flow condensation for refrigerant R134a in the tube partially filled with annular metal foam are experimentally investigated to overcome the disadvantage of large pressure drop for tubes fully filled with metal foam. The tube wall temperatures are measured with thermal couples to determine the heat transfer coefficient. The effects of mass flux and vapor quality of two-phase fluid on the pressure drop and heat transfer coefficient are analyzed accordingly. It is found that the pressure drop of tubes partially filled with metal-foam is much higher than that of smooth tubes and the pressure drop increases non-linearly and greatly as the mass flux and vapor quality increase. The flow regime is predicted by monitoring the distribution and fluctuation of crosssection temperatures, from which the stratified wavy flow and annular flow are detected. It is also revealed that the flow condensation heat

  2. Numerical investigations of two-phase spray combustion flow fields in slinger annular combustor%折流燃烧室两相喷雾燃烧流场数值模拟

    Institute of Scientific and Technical Information of China (English)

    颜应文; 宋双文; 胡好生; 王倚阳; 雷雨冰; 赵坚行; 林志勇

    2011-01-01

    在任意曲线坐标系下对折流燃烧室两相喷雾燃烧流场进行数值模拟,采用偏微分方程法生成三维贴体网格,采用k-ε双方程模型模拟湍流黏性,分别采用EBU(eddy break-up)-Arrhenius燃烧模型、EDC(eddy díssipation concept)燃烧模型以及二阶矩(second-order-moment,简称SOM)燃烧模型模拟化学反应速率,在非交错网格下,采用欧拉-拉格朗日方法模拟气液两相喷雾燃烧过程,气液之间相互耦合采用PSIC(particle-source-in-cell)算法求解.数值分析不同湍流燃烧模型对折流燃烧室两相喷雾燃烧流场的影响,计算结果与试验数据比较,表明采用不同湍流燃烧模型所得的两相喷雾燃烧流场有所不同,其中SOM燃烧模型和EBU燃烧模型都能较好地数值模拟折流燃烧室两相喷雾燃烧过程.%In arbitrary curvilinear coordinates, numerical investigations of three-dimensional two-phase spray combustion flow fields for a slinger annular combustor were carried out. Three-dimensional body-fitted grids were generated by TTM (Thompson-Thames-Martin) method, k-ε model was used to simulate the turbulent viscosity; EBU (eddy break-up)Arrhenius combustion model, EDC (eddy dissipation concept) combustion model and SOM (second-order-moment) combustion model were applied to predict turbulent combustion rate. The gas and liquid phases were treated with Eulerian-Lagrangian method and the gasliquid coupling was calculated with PSIC (particle-source-in-cell) arithmetic. The effects of different combustion models on two-phase spray combustion flow fields were studied. The numerical results are in good agreement with the experimental data. It shows that all of the combustion models are used to simulate the combustion process in slinger annular combustor, but the SOM combustion model and EBU combustion model are better than EDC combustion model for simulation of two-phase spray combustion flow fields in the slinger annular combustor.

  3. Biosensor Arrays for Estimating Molecular Concentration in Fluid Flows

    CERN Document Server

    Abolfath-Beygi, Maryam

    2011-01-01

    This paper constructs dynamical models and estimation algorithms for the concentration of target molecules in a fluid flow using an array of novel biosensors. Each biosensor is constructed out of protein molecules embedded in a synthetic cell membrane. The concentration evolves according to an advection-diffusion partial differential equation which is coupled with chemical reaction equations on the biosensor surface. By using averaging theory methods and the divergence theorem, an approximate model is constructed that describes the asymptotic behaviour of the concentration as a system of ordinary differential equations. The estimate of target molecules is then obtained by solving a nonlinear least squares problem. It is shown that the estimator is strongly consistent and asymptotically normal. An explicit expression is obtained for the asymptotic variance of the estimation error. As an example, the results are illustrated for a novel biosensor built out of protein molecules.

  4. Phase Split of Slug-Annular Flow at Micro Impacting Junctions%冲击型微小三通内弹环状流的相分配特性

    Institute of Scientific and Technical Information of China (English)

    陈锦芳; 余康华; 李选友; 汪双凤

    2014-01-01

    本文在入口条件为弹环状流的条件下,考察了氮气-水两相流在水力直径为0.5 mm的水平等径冲击型三通中的相分配特性.根据入口与两个分支夹角的不同,冲击型三通分为T型冲击三通和Y型冲击三通.结果发现:相分配受入口流型的影响因冲击角而异.对于T型三通,入口流型对相分配的影响较小;而对于Y型三通,随着入口条件从靠近弹状流区域过渡到靠近环状流区域,相分配往等干度分配线靠近.变动冲击角对气液两相流的相分配有一定的影响,影响程度因入口条件而异.%The present work studies the phase splitting characteristics of water-nitrogen slug-annular flow at equal-sided impacting junctions with diameter of 0.5 mm.Impacting junctions may be divided into T-shaped junction and Y-shaped junction according to the different impacting angles between the inlet and either branch.The test results show that the effect of inlet flow patterns on phase split depends on the impacting angles.For the case of the impacting T-shaped junction,the effect of inlet flow patterns on phase split is small.However,for the case of impacting Y-shaped junctions,the phase splitting curve moves towards the equal splitting line as the inlet flow pattern shifts from the zone close to slug flow to the zone close to annular flow.In addition,the impacting angles have influence on phase split,but the influence is dependent on inlet flow conditions.

  5. Excitation by flows in seals and clearances. Part 1: Introduction: Fluid-structure-interactions in rotordynamics. Part 2: Identification of rotordynamic coefficients of annular seals

    Science.gov (United States)

    Nordmann, R.

    The fluid-structure interactions in rotor dynamics and the identification of rotor dynamic coefficients of annular seals are studied. The different fluid forces acting in the neck ring, the interstage seals, the balance pistons, the impellers and the oil film bearings of pumps are reviewed. These forces can have a large influence on the bending vibrations of a pump rotor. Theoretical and experimental models of fluid elements and of rotordynamics are presented. Simulations of the rotordynamic behavior show that the fluid forces of most elements can be described by linear-force relations. A theoretical model and an indentification procedure are presented to determine the dynamic coefficients of seals. The identified parameters confirm the assumptions in modeling and point out that the stiffness and damping characteristics of seals are significant for the stability behavior of pumps.

  6. [Disseminated granuloma annulare].

    Science.gov (United States)

    Kansky, A

    1975-09-01

    A case of generalized granuloma annulare in a 55 year old man is reported. The disease appeared five years before the first admission to the hospital. A large number of bluish-red or skin-colour papules were scattered mainly around the earlobes, buttocks and on the extremities. Some of the lesions were lined up in rings or plaques. Small depigmented and brownish scars were present. Two biopsies revealed characteristic foci of complete collagen degeneration accompanied by a palisading infiltrate in the upper dermis. Treatment with tuberculostatics and antimalarics was without improvement. The lesions cleared after a course of prednison, but reappeared when the drug was discontinued.

  7. Ozone concentrations in air flowing into New York State

    Science.gov (United States)

    Aleksic, Nenad; Kent, John; Walcek, Chris

    2016-09-01

    Ozone (O3) concentrations measured at Pinnacle State Park (PSPNY), very close to the southern border of New York State, are used to estimate concentrations in air flowing into New York. On 20% of the ozone season (April-September) afternoons from 2004 to 2015, mid-afternoon 500-m back trajectories calculated from PSPNY cross New York border from the south and spend less than three hours in New York State, in this area of negligible local pollution emissions. One-hour (2p.m.-3p.m.) O3 concentrations during these inflowing conditions were 46 ± 13 ppb, and ranged from a minimum of 15 ppb to a maximum of 84 ppb. On average during 2004-2015, each year experienced 11.8 days with inflowing 1-hr O3 concentrations exceeding 50 ppb, 4.3 days with O3 > 60 ppb, and 1.5 days had O3 > 70 ppb. During the same period, 8-hr average concentrations (10a.m. to 6p.m.) exceeded 50 ppb on 10.0 days per season, while 3.9 days exceeded 60 ppb, and 70 ppb was exceeded 1.2 days per season. Two afternoons of minimal in-state emission influences with high ozone concentrations were analyzed in more detail. Synoptic and back trajectory analysis, including comparison with upwind ozone concentrations, indicated that the two periods were characterized as photo-chemically aged air containing high inflowing O3 concentrations most likely heavily influenced by pollution emissions from states upwind of New York including Pennsylvania, Tennessee, West Virginia, and Ohio. These results suggest that New York state-level attempts to comply with National Ambient Air Quality Standards by regulating in-state O3 precursor NOx and organic emissions would be very difficult, since air frequently enters New York State very close to or in excess of Federal Air Quality Standards.

  8. Premixed double concentric jets flame with swirl flow

    Energy Technology Data Exchange (ETDEWEB)

    Ito, K.; Song, K.

    1987-01-01

    Swirl flow has been commonly used for stabilization of the high-intensity combustion process. The swirl flow is imparted to the secondary airflow by the swirl vane. Flame stability limits, flame shapes, the concentration of combustion gas, and the temperature distribution in the recirculation zone were measured, and high-speed schlieren photographs were taken. The results indicate that flame stability limits decrease with increasing swirl number in weak swirls because the mixture deteriorates due to the swirl in the recirculation zone. But an increase with increasing swirl number in strong swirls is seen in the mixing ratio, which is promoted by the swirl. For no swirl or weak swirls, a recirculation zone formed behind the burner rim affects the flame stability. When there is a strong swirl, a recirculation zone formed by the swirl affects the flame stability. 9 references.

  9. Percolation velocity dependence on local concentration in bidisperse granular flows

    Science.gov (United States)

    Jones, Ryan P.; Xiao, Hongyi; Deng, Zhekai; Umbanhowar, Paul B.; Lueptow, Richard M.

    The percolation velocity, up, of granular material in size or density bidisperse mixtures depends on the local concentration, particle size ratio, particle density ratio, and shear rate, γ ˙. Discrete element method computational results were obtained for bounded heap flows with size ratios between 1 and 3 and for density ratios between 1 and 4. The results indicate that small particles percolate downward faster when surrounded by large particles than large particles percolate upward when surrounded by small particles, as was recently observed in shear-box experiments. Likewise, heavy particles percolate downward faster when surrounded by light particles than light particles percolate upward when surrounded by heavy particles. The dependence of up / γ ˙ on local concentration results in larger percolation flux magnitudes at high concentrations of large (or light) particles compared to high concentrations of small (or heavy) particles, while local volumetric flux is conserved. The dependence of up / γ ˙ on local concentration can be incorporated into a continuum model, but the impact on global segregation patterns is usually minimal. Partially funded by Dow Chemical Company and NSF Grant No. CBET-1511450.

  10. Characteristics of Electrorheological Fluid Flow Between Two Concentric Cylinders

    Institute of Scientific and Technical Information of China (English)

    PENG Jie; ZHU Ke-Qin; XI Bao-Shu

    2000-01-01

    The characteristics of Couette flow of electrorheological fluid (ERF) between concentric cylinders is dependent on the parameter β, which is in the yield stress formula of ERF. In the case of β > 2, the yield region locates between the yield surface and the outer cylinder. In the case of β < 2, the yield region locates between the yield surface and the inner cylinder. When β=2, there is no yield surface. Steady and time dependent numerical results in relation to different β are presented and discussed.

  11. Portal Annular Pancreas

    Science.gov (United States)

    Harnoss, Jonathan M.; Harnoss, Julian C.; Diener, Markus K.; Contin, Pietro; Ulrich, Alexis B.; Büchler, Markus W.; Schmitz-Winnenthal, Friedrich H.

    2014-01-01

    Abstract Portal annular pancreas (PAP) is an asymptomatic congenital pancreas anomaly, in which portal and/or mesenteric veins are encased by pancreas tissue. The aim of the study was to determine the role of PAP in pancreatic surgery as well as its management and potential complication, specifically, postoperative pancreatic fistula (POPF). On the basis of a case report, the MEDLINE and ISI Web of Science databases were systematically reviewed up to September 2012. All articles describing a case of PAP were considered. In summary, 21 studies with 59 cases were included. The overall prevalence of PAP was 2.4% and the patients' mean (SD) age was 55.9 (16.2) years. The POPF rate in patients with PAP (12 pancreaticoduodenectomies and 3 distal pancreatectomies) was 46.7% (in accordance with the definition of the International Study Group of Pancreatic Surgery). Portal annular pancreas is a quite unattended pancreatic variant with high prevalence and therefore still remains a clinical challenge to avoid postoperative complications. To decrease the risk for POPF, attentive preoperative diagnostics should also focus on PAP. In pancreaticoduodenectomy, a shift of the resection plane to the pancreas tail should be considered; in extensive pancreatectomy, coverage of the pancreatic remnant by the falciform ligament could be a treatment option. PMID:25207658

  12. Investigating droplet internal flow in concentrated emulsion when flowing in microchannel using micro-PIV

    Science.gov (United States)

    Leong, Chia Min; Gai, Ya; Tang, Sindy K. Y.

    2016-11-01

    Droplet microfluidics has enabled a wide variety of high throughput applications through the use of monodisperse droplets. Previous fluid studies of droplet microfluidics have focused on single drops or emulsions at low volume fractions. The study of concentrated emulsions at high volume fractions is important for increasing the throughput, but the fluid dynamics of such emulsions in confined channels is not well understood. Here we describe two-dimensional, mid-height measurements of the flow inside individual drops within a concentrated emulsion using micro-PIV. The emulsion has 85% volume fraction and flows as a monolayer in a straight microfluidic channel. The effects of confinement and viscosity ratio on the internal flow patterns inside the drops were studied. The results show rotational structures inside the drops always exist, and are independent of viscosity ratio for the conditions tested. The structures depend on droplet mobility which in turn, depends on the confinement of the emulsion and the location of the drops in the channel. To our best knowledge, no work has probed the flow field inside droplets of concentrated emulsions at high volume fractions in confined channels. Current work is in progress to measure the three-dimensional flow field in such system.

  13. A Study of a Powder Coating Gun near Field: A Case of Staggered Concentric Jet Flow

    Directory of Open Access Journals (Sweden)

    Edward Grandmaison

    2013-11-01

    Full Text Available This paper examines, experimentally and numerically, an isothermal coaxial air jet, created by an innovative nozzle design for an air propane torch, used for the thermal deposition of polymers. This design includes staggering the origins of the central and annular jets and creating an annular air jet with an inward radial velocity component. The experimental work used a Pitot tube to measure axial velocity on the jet centerline and in the fully developed flow. The static gauge pressure in the near field was also measured and found to be positive, an unexpected result. The numerical work used Gambit and Fluent. An extensive grid sensitivity study was conducted and it was found that results from a relatively coarse mesh were substantially the same as results from a mesh with almost 11 times the number of control volumes. A thorough evaluation of all of the RANS models in Fluent 6.3.26 found that the flow fields they calculated showed at most partial agreement with the experimental results. The greatest difference between numerical and experimental results was the incorrect prediction by all RANS models of a recirculation zone in the near field on the jet axis. Experimental work showed it did not exist.

  14. MODELING HEADCUT DEVELOPMENT AND MIGRATION IN UPLAND CONCENTRATED FLOWS

    Institute of Scientific and Technical Information of China (English)

    Sean J. BENNETT; Carlos V. ALONSO

    2005-01-01

    On hillslopes and agricultural fields, discrete areas of intense, localized soil erosion commonly take place in the form of migrating headcuts. These erosional features significantly increase soil loss and landscape degradation, yet the unsteady, transient, and migratory habits of headcuts complicate their phenomenological and erosional characterization. Here a unique experimental facility was constructed to examine actively migrating headcuts typical of upland concentrated flows. Essential components of the facility include a deep soil cavity with external drainage, rainfall simulator, capacity for overland flow, and a video recording technique for data collection. Results from these experiments show that:(1) after a short period of adjustment, headcut migration attained a steady-state condition, where the rate of migration, scour hole geometry, and sediment discharge remain constant with time; (2)boundary conditions of higher rates of overland flow, steeper bed slopes, and larger initial headcut heights produced systematically larger scour holes with higher rates of soil erosion; and (3) during migration, the turbulent flow structure within the scour hole remained unchanged, consisting of an overfall nappe at the brink transitioning into a reattached wall jet with two recirculation eddies within the plunge pool. The systematic behavior of headcut development and migration enabled the application of modified jet impingement theory to predict with good success the characteristics of the impinging jet, the depth of maximum scour, the rate of headcut migration, and the rate of sediment erosion. These laboratory data and the analytical formulation can be used in conjunction with soil erosion prediction technology to improve the management of agricultural areas impacted by headcut development and ephemeral gully erosion.

  15. An Annular Gap Acceleration Model for γ-ray Emission of Pulsars

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    If the binding energy of the pulsar's surface is not so high (the case of a neutron star), both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for γ-ray emission of pulsars is suggested. It is emphasized that:(1) Two kinds of acceleration regions (annular and core) need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. (2) If the potential drop in the annular region of a pulsar is high enough (normally the case for young pulsars), charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. (3) The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. (4)The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the γ-ray emission from the annular flow are analogous to that presented in a previous work by Qiao et al., which match the observations well. (5) Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved.

  16. Non newtonian annular alloy solidification in mould

    Energy Technology Data Exchange (ETDEWEB)

    Moraga, Nelson O.; Garrido, Carlos P. [Universidad de La Serena, Departamento de Ingenieria Mecanica, La Serena (Chile); Castillo, Ernesto F. [Universidad de Santiago de Chile, Departamento de Ingenieria Mecanica, Santiago (Chile)

    2012-08-15

    The annular solidification of an aluminium-silicon alloy in a graphite mould with a geometry consisting of horizontal concentric cylinders is studied numerically. The analysis incorporates the behavior of non-Newtonian, pseudoplastic (n=0.2), Newtonian (n=1), and dilatant (n=1.5) fluids. The fluid mechanics and heat transfer coupled with a transient model of convection diffusion are solved using the finite volume method and the SIMPLE algorithm. Solidification is described in terms of a liquid fraction of a phase change that varies linearly with temperature. The final results make it possible to infer that the fluid dynamics and heat transfer of solidification in an annular geometry are affected by the non-Newtonian nature of the fluid, speeding up the process when the fluid is pseudoplastic. (orig.)

  17. A stochastic approach to the flow-concentration curve in traffic flow theory

    CERN Document Server

    Qian, Wei-Liang; Lin, Kai; Siqueira, Adriano F

    2016-01-01

    An alternative stochastic model for the fundamental diagram of traffic flow with minimal number of parameters is proposed. The key features of the model lie in its "catastrophic" potential function as well as in its stochastic nature, which makes it possible to describe the main features of the flow-concentration relation. In particular, the inverse-$\\lambda$ shape as well as the wide scattering of congested traffic data are both reproduced. In our model, the scattering of the data is attributed to the noise terms introduced in the stochastic differential equations. The inverse-$\\lambda$ shape and the associated sudden jump of physical quantities arise, on the other hand, due to the existence of two simultaneous stable traffic flow states and/or to the effect of stochastic noises on the stability of the system. The model parameters are calibrated and compared qualitatively with the data.

  18. Internal flow in droplets within a concentrated emulsion flowing in a microchannel

    Science.gov (United States)

    Leong, Chia Min; Gai, Ya; Tang, Sindy K. Y.

    2016-11-01

    Droplet microfluidics has enabled a wide variety of high-throughput biotechnical applications through the use of monodisperse micro-droplets as bioreactors. Previous fluid dynamics studies of droplet microfluidics have focused on single droplets or emulsions at low volume fractions. The study of concentrated emulsions at high volume fractions is important for further increasing the throughput of droplet microfluidics, but the fluid dynamics of such emulsions in confined microchannels is not well understood. This paper describes the use of microscopic particle image velocimetry to quantify the flow inside individual droplets within a concentrated emulsion having volume fraction φ ˜ 85% flowing as a monolayer in a straight microfluidic channel. The effects of confinement (namely, the number of rows of droplets across the width of the channel) and viscosity ratio on the internal flow patterns inside the drops at a fixed capillary number of 10-3 and a Reynolds number of 10-2 to 10-1 are studied. The results show that rotational structures inside the droplets always exist and are independent of viscosity ratio for the conditions tested. The structures depend on droplet mobility, the ratio of the velocity of the droplet to the velocity of the continuous phase. These values, in turn, depend on the confinement of the emulsion and the location of the droplets in the channel. Although this work presents two-dimensional measurements at the mid-height of the microchannel only, the results reveal flow patterns that are never described before in single drops or dilute emulsions.

  19. Annular Hybrid Rocket Motor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Engineers at SpaceDev have conducted a preliminary design and analysis of a proprietary annular design concept for a hybrid motor. A U.S. Patent application has been...

  20. Annular Elastolytic Giant Cell Granuloma

    Directory of Open Access Journals (Sweden)

    Khandpur Sujay

    2001-01-01

    Full Text Available The clinical and histopathological features of annular elastolytic giant cell granuloma in a 42â€"year-old female patient are described. The condition presented as annular erythematous plaques over sun- exposed skin sparing the face. Histopathology revealed dense granulomatous infiltrate consisting of numerous giant cells and lymphohistiocytes without any palisading arrangement or necrobiosis. The features differentiating it from other similar granulomatous disorders are discussed.

  1. Manufacture of annular cermet articles

    Science.gov (United States)

    Forsberg, Charles W.; Sikka, Vinod K.

    2004-11-02

    A method to produce annular-shaped, metal-clad cermet components directly produces the form and avoids multiple fabrication steps such as rolling and welding. The method includes the steps of: providing an annular hollow form with inner and outer side walls; filling the form with a particulate mixture of ceramic and metal; closing, evacuating, and hermetically sealing the form; heating the form to an appropriate temperature; and applying force to consolidate the particulate mixture into solid cermet.

  2. Mid-section of a can-annular gas turbine engine with an improved rotation of air flow from the compressor to the turbine

    Energy Technology Data Exchange (ETDEWEB)

    Little, David A.; Schilp, Reinhard; Ross, Christopher W.

    2016-03-22

    A midframe portion (313) of a gas turbine engine (310) is presented and includes a compressor section with a last stage blade to orient an air flow (311) at a first angle (372). The midframe portion (313) further includes a turbine section with a first stage blade to receive the air flow (311) oriented at a second angle (374). The midframe portion (313) further includes a manifold (314) to directly couple the air flow (311) from the compressor section to a combustor head (318) upstream of the turbine section. The combustor head (318) introduces an offset angle in the air flow (311) from the first angle (372) to the second angle (374) to discharge the air flow (311) from the combustor head (318) at the second angle (374). While introducing the offset angle, the combustor head (318) at least maintains or augments the first angle (372).

  3. Mid-section of a can-annular gas turbine engine with a radial air flow discharged from the compressor section

    Energy Technology Data Exchange (ETDEWEB)

    Little, David A.; McQuiggan, Gerard; Wasdell, David L.

    2016-10-25

    A midframe portion (213) of a gas turbine engine (210) is presented, and includes a compressor section (212) configured to discharge an air flow (211) directed in a radial direction from an outlet of the compressor section (212). Additionally, the midframe portion (213) includes a manifold (214) to directly couple the air flow (211) from the compressor section (212) outlet to an inlet of a respective combustor head (218) of the midframe portion (213).

  4. Mid-section of a can-annular gas turbine engine with a radial air flow discharged from the compressor section

    Science.gov (United States)

    Little, David A.; McQuiggan, Gerard; Wasdell, David L.

    2016-10-25

    A midframe portion (213) of a gas turbine engine (210) is presented, and includes a compressor section (212) configured to discharge an air flow (211) directed in a radial direction from an outlet of the compressor section (212). Additionally, the midframe portion (213) includes a manifold (214) to directly couple the air flow (211) from the compressor section (212) outlet to an inlet of a respective combustor head (218) of the midframe portion (213).

  5. The effect of the inner cylinder rotation on the fluid dynamics of non-Newtonian fluids in concentric and eccentric annuli

    Directory of Open Access Journals (Sweden)

    J. L. Vieira Neto

    2014-12-01

    Full Text Available Helical flow in an annular space occurs during oil drilling operations. The correct prediction of flow of drilling fluid in an annular space between the wellbore wall and the drill pipe is essential to determine the variation in fluid pressure within the wellbore. This paper presents experimental and CFD simulation results of the pressure drop in the flow of non-Newtonian fluids through a concentric annular section and another section with fixed eccentricity (E = 0.75, using aqueous solutions of two distinct polymers (Xanthan Gum and Carboxymethylcellulose. The hydrodynamic behavior in this annular system was analyzed based on the experimental and CFD results, providing important information such as the formation of zones with preferential flows and stagnation regions.

  6. Modeling and control of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Vries, D.; Mourik, van S.; Zwart, H.

    2007-01-01

    Abstract¿ As an alternative or addition to complex physical modeling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the

  7. Modelling of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Parasoglou, M.; Vries, D.

    2006-01-01

    As an alternative or addition to complex physical modelling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the control s

  8. Modeling and control of water disinfection process in annular photoreactors

    NARCIS (Netherlands)

    Keesman, K.J.; Vries, D.; Mourik, van S.; Zwart, H.J.; Tzafestas, S.

    2007-01-01

    As an alternative or addition to complex physical modeling, in this paper transfer function models of the disinfection process in annular photoreactors under different flow conditions are derived. These transfer function models allow an analytical evaluation of the system dynamics and the control st

  9. The influence of the tangential velocity of inner rotating wall on axial velocity profile of flow through vertical annular pipe with rotating inner surface

    Directory of Open Access Journals (Sweden)

    Sharf Abdusalam M.

    2014-03-01

    Full Text Available In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig and computational (employing CFD software investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.

  10. Influence of Irradiance, Flow Rate, Reactor Geometry, and Photopromoter Concentration in Mineralization Kinetics of Methane in Air and in Aqueous Solutions by Photocatalytic Membranes Immobilizing Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    Ignazio Renato Bellobono

    2008-01-01

    Full Text Available Photomineralization of methane in air (10.0–1000 ppm (mass/volume of C at 100% relative humidity (dioxygen as oxygen donor was systematically studied at 318±3 K in an annular laboratory-scale reactor by photocatalytic membranes immobilizing titanium dioxide as a function of substrate concentration, absorbed power per unit length of membrane, reactor geometry, and concentration of a proprietary vanadium alkoxide as photopromoter. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC disappearance, to yield carbon dioxide, were followed. At a fixed value of irradiance (0.30 W⋅cm-1, the mineralization experiments in gaseous phase were repeated as a function of flow rate (4–400 m3⋅h−1. Moreover, at a standard flow rate of 300 m3⋅h−1, the ratio between the overall reaction volume and the length of the membrane was varied, substantially by varying the volume of reservoir, from and to which circulation of gaseous stream took place. Photomineralization of methane in aqueous solutions was also studied, in the same annular reactor and in the same conditions, but in a concentration range of 0.8–2.0 ppm of C, and by using stoichiometric hydrogen peroxide as an oxygen donor. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters, k1 and K1, k2 and K2, were calculated, which is able to fit the whole kinetic profile adequately. The influence of irradiance on k1 and k2, as well as of flow rate on K1 and K2, is rationalized. The influence of reactor geometry on k values is discussed in view of standardization procedures of photocatalytic experiments. Modeling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photopromoter, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or

  11. Visualizing the internal structure of subaqueous, high-concentration sediment-laden flows: implication of rheology to flow structure

    Science.gov (United States)

    Perillo, M. M.; Buttles, J.; Mohrig, D. C.; Kane, I.; Pontén, A.; Brown, D.; Minton, B. W.

    2013-12-01

    Subaqueous sediment-laden flows are thought to be the main mechanism transporting sediments to the deep sea. Understanding the processes governing these flows is crucial to building predictive models of flow behaviour, sediment transport and deposition and is applicable to a wide range of disciplines. Physical modelling using a wide range of experimental facilities and measurement techniques has significantly advanced our understanding of these sediment-laden flows and their ability to erode, transport and deposit sediments. However, for the case of high-sediment concentration flows, measuring flow and depositional properties is still a challenge. Here, we present results from an acoustic reflection technique that allows for direct and noninvasive visualization of the internal structure of high concentration, clay-rich, sand-laden flows with a range of initial yield strengths (0-26 Pa). As the acoustic signal travels through the sediment-laden flow, it encounters zones of varying acoustic impedance that are due to temporal and spatial changes in sediment concentration, grain size and sorting, and flow mixing. The reflected signal is processed and interpreted using seismic techniques developed in exploration geophysics. The ultrasonic reflection data captured two distinct flow stages, an active stage and a post-depositional creeping stage. The clay-rich sand-laden flows showed stratification expressed by three clear vertical zones: (a) an upper relatively dilute turbulent zone, (b) a zone with high sediment concentration and significantly reduced mixing and (c) an aggrading bed of static grains.

  12. Annular lipoatrophy of the ankles.

    Science.gov (United States)

    Dimson, Otobia G; Esterly, Nancy B

    2006-02-01

    Lipoatrophic panniculitis likely represents a group of disorders characterized by an inflammatory panniculitis followed by lipoatrophy. It occurs locally in a variety of settings and has been reported in the literature under various terms, including annular atrophic connective tissue panniculitis of the ankles, annular and semicircular lipoatrophy, abdominal lipoatrophy, and connective tissue panniculitis. Herein, a case of annular lipoatrophy of the ankles is described in a 6-year-old girl with autoimmune thyroid disease. Histologically, a mixed lobular panniculitis with lipophages was present. This pattern resembles that seen in lipoatrophic panniculitis. After a single, acute episode of an inflammatory process with subsequent lipoatrophy, her skin lesions have stabilized for 2 years requiring no treatment.

  13. Numerical Simulation of Turbulent Flow in Concentric Annuli

    OpenAIRE

    Boersma, B.J.; Breugem, W.-P.

    2010-01-01

    In this paper we consider a fully developed turbulent flow in a round pipe with a small inner annulus. The diameter of the inner annulus is less than 10% of the diameter of the outer pipe. As a consequence, the surface area of the inner pipe compared to the outer pipe is small. The friction exerted by the wall on the flow is proportional to the surface area and the wall shear stress. Due to the small surface area of the inner annulus the additional stress on the flow due to the presence of th...

  14. Eosinophilic annular erythema in childhood - Case report*

    Science.gov (United States)

    Abarzúa, Alvaro; Giesen, Laura; Silva, Sergio; González, Sergio

    2016-01-01

    Eosinophilic annular erythema is a rare, benign, recurrent disease, clinically characterized by persistent, annular, erythematous lesions, revealing histopathologically perivascular infiltrates with abundant eosinophils. This report describes an unusual case of eosinophilic annular erythema in a 3-year-old female, requiring sustained doses of hydroxychloroquine to be adequately controlled. PMID:27579748

  15. Mathematical Model of Combustion in Blunt Annular Ceramic Burner

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The computer simulation of the combustion process in blast furnace (BF) stove has been studied by using the k-ε-g turbulent diffusion flame model. The combustion process in blunt annular ceramic burner was calculated by using the software. The profiles of gas and air velocity, temperature of the combustion products, concentration of the components, and the shape and length of the flame during combustion have been researched . Compared with the original annular ceramic burner, the new design of the blunt one improves the mixing of the gas and the air significantly, and shortened the length of the flame.

  16. Entrance and exit region friction factor models for annular seal analysis. Ph.D. Thesis

    Science.gov (United States)

    Elrod, David Alan

    1988-01-01

    The Mach number definition and boundary conditions in Nelson's nominally-centered, annular gas seal analysis are revised. A method is described for determining the wall shear stress characteristics of an annular gas seal experimentally. Two friction factor models are developed for annular seal analysis; one model is based on flat-plate flow theory; the other uses empirical entrance and exit region friction factors. The friction factor predictions of the models are compared to experimental results. Each friction model is used in an annular gas seal analysis. The seal characteristics predicted by the two seal analyses are compared to experimental results and to the predictions of Nelson's analysis. The comparisons are for smooth-rotor seals with smooth and honeycomb stators. The comparisons show that the analysis which uses empirical entrance and exit region shear stress models predicts the static and stability characteristics of annular gas seals better than the other analyses. The analyses predict direct stiffness poorly.

  17. Study on the annular leakage-flow-induced vibrations. 2nd Report. Stability analysis and experiments for translationally and rotationally coupled two-degree-of-freedom systems; Kanjo sukimaryu reiki shindo ni kansuru kenkyu. 2. heishin kaiten 2 jiyudo renseikei no anteisei kaiseki oyobi jikken

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.W. [Hitachi, Ltd., Tokyo (Japan); Kaneko, S. [The University of Tokyo, Tokyo (Japan); Hayama, S. [Toyama Prefectural University, Toyama (Japan)

    1999-07-25

    In this study, the stability of annular leakage-flow-induced vibrations was investigated theoretically and experimentally for a translationally and rotationally coupled two-degree-of-freedom system. The critical flow rate was both theoretically and experimentally obtained as a function of the passage increment ratio and the eccentricity of the passage. A good agreement between the theoretical and experimental results was obtained. It was discovered both theoretically and from the experiments that instability will occur in the case of a divergent passage: the eccentricity of the passage lowers the stability of the systems. (author)

  18. EXPERIMENTAL INVESTIGATIONS ON DIFFUSION CHARACTERISTICS OF HIGH CONCENTRATION JET FLOW IN NEAR REGION

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The diffusion characteristics of the high concentration jet flowissued from a round nozzle above the free surface into moving waterbody were experimentally investigated. By means of flow visualization technique, the diffusion behavior of the high concentration jet was observed and analysed, Concentration distribution in the near region was obtained by sampling and quantitative measurements. Experimental results indicate that the diffusion mechanics of the high concentration jet flow are greatly influenced by initial momentum, buoyancy, turbulent structure, ambient current and boundary conditions, showing complicated flow patterns and concentration distribution characteristics that are different from previous results for submerged jets.

  19. Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain,Northeast China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Overwhelming evidence reveals that concentrations of dissolved organic carbon (DOC) have increased in streams which brings negative environmental impacts.DOC in stream flow is mainly originated from soil-water solutions of watershed.Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems.This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland,i.e.,a dishing wetland and a forest wetland together,in the Sanjiang Plain.Northeast China.The results indicate that DOC concentrations in soil-water solutions decreased and then increased with increasing soil depth in the annular wetland.In the upper soil layers of 0-10 cm and 10-20 cm,DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland (R2=0.3122 and R2=0.443).The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions.The concentrations of total organic carbon (TOC),total carbon (TC) and Fe(Ⅱ),DOC mobility and continuous vertical and lateral flow affected the distribution variations of DOC in soil-water solutious.The correlation coefficients between DOC concentrations and TOC,TC and Fe(Ⅱ) were 0.974,0.813 and 0.753 respectively.These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments.However,the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale.These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports,which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

  20. Numerical Simulation of Turbulent Flow in Concentric Annuli

    NARCIS (Netherlands)

    Boersma, B.J.; Breugem, W.-P.

    2010-01-01

    In this paper we consider a fully developed turbulent flow in a round pipe with a small inner annulus. The diameter of the inner annulus is less than 10% of the diameter of the outer pipe. As a consequence, the surface area of the inner pipe compared to the outer pipe is small. The friction exerted

  1. Prediction of concentrated flow width in ephemeral gully channels

    Science.gov (United States)

    Nachtergaele, J.; Poesen, J.; Sidorchuk, A.; Torri, D.

    2002-07-01

    Empirical prediction equations of the form W = aQb have been reported for rills and rivers, but not for ephemeral gullies. In this study six experimental data sets are used to establish a relationship between channel width (W, m) and flow discharge (Q, m3 s-1) for ephemeral gullies formed on cropland. The resulting regression equation (W = 2·51 Q0·412; R2 = 0·72; n = 67) predicts observed channel width reasonably well. Owing to logistic limitations related to the respective experimental set ups, only relatively small runoff discharges (i.e. Q flow channels revealed that the discharge exponent (flow shear stress distribution over the wetted perimeter between rills, gullies and rivers, (ii) a decrease in probability of a channel formed in soil material with uniform erosion resistance from rills over gullies to rivers and (iii) a decrease in average surface slope from rills over gullies to rivers.material. For both cases observed flow on cropland. For the frozen soils the equation

  2. Numerical Simulation of Turbulent Flow in Concentric Annuli

    NARCIS (Netherlands)

    Boersma, B.J.; Breugem, W.-P.

    2010-01-01

    In this paper we consider a fully developed turbulent flow in a round pipe with a small inner annulus. The diameter of the inner annulus is less than 10% of the diameter of the outer pipe. As a consequence, the surface area of the inner pipe compared to the outer pipe is small. The friction exerted

  3. Design and analysis of 19 pin annular fuel rod cluster for pressure tube type boiling water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Deokule, A.P., E-mail: abhijit.deokule1986@gmail.com [Homi Bhabha National Institute, Trombay 400 085, Mumbai (India); Vishnoi, A.K.; Dasgupta, A.; Umasankari, K.; Chandraker, D.K.; Vijayan, P.K. [Bhabha Atomic Research Centre, Trombay 400 085, Mumbai (India)

    2014-09-15

    Highlights: • Development of 19 pin annular fuel rod cluster. • Reactor physics study of designed annular fuel rod cluster. • Thermal hydraulic study of annular fuel rod cluster. - Abstract: An assessment of 33 pin annular fuel rod cluster has been carried out previously for possible use in a pressure tube type boiling water reactor. Despite the benefits such as negative coolant void reactivity and larger heat transfer area, the 33 pin annular fuel rod cluster is having lower discharge burn up as compared to solid fuel rod cluster when all other parameters are kept the same. The power rating of this design cannot be increased beyond 20% of the corresponding solid fuel rod cluster. The limitation on the power is not due to physics parameters rather it comes from the thermal hydraulics side. In order to increase power rating of the annular fuel cluster, keeping same pressure tube diameter, the pin diameter was increased, achieving larger inside flow area. However, this reduces the number of annular fuel rods. In spite of this, the power of the annular fuel cluster can be increased by 30% compared to the solid fuel rod cluster. This makes the nineteen pin annular fuel rod cluster a suitable option to extract more power without any major changes in the existing design of the fuel. In the present study reactor physics and thermal hydraulic analysis carried out with different annular fuel rod cluster geometry is reported in detail.

  4. Annular MHD Physics for Turbojet Energy Bypass

    Science.gov (United States)

    Schneider, Steven J.

    2011-01-01

    The use of annular Hall type MHD generator/accelerator ducts for turbojet energy bypass is evaluated assuming weakly ionized flows obtained from pulsed nanosecond discharges. The equations for a 1-D, axisymmetric MHD generator/accelerator are derived and numerically integrated to determine the generator/accelerator performance characteristics. The concept offers a shockless means of interacting with high speed inlet flows and potentially offers variable inlet geometry performance without the complexity of moving parts simply by varying the generator loading parameter. The cycle analysis conducted iteratively with a spike inlet and turbojet flying at M = 7 at 30 km altitude is estimated to have a positive thrust per unit mass flow of 185 N-s/kg. The turbojet allowable combustor temperature is set at an aggressive 2200 deg K. The annular MHD Hall generator/accelerator is L = 3 m in length with a B(sub r) = 5 Tesla magnetic field and a conductivity of sigma = 5 mho/m for the generator and sigma= 1.0 mho/m for the accelerator. The calculated isentropic efficiency for the generator is eta(sub sg) = 84 percent at an enthalpy extraction ratio, eta(sub Ng) = 0.63. The calculated isentropic efficiency for the accelerator is eta(sub sa) = 81 percent at an enthalpy addition ratio, eta(sub Na) = 0.62. An assessment of the ionization fraction necessary to achieve a conductivity of sigma = 1.0 mho/m is n(sub e)/n = 1.90 X 10(exp -6), and for sigma = 5.0 mho/m is n(sub e)/n = 9.52 X 10(exp -6).

  5. PASSIVE CONTROL OF PARTICLE DISPERSION IN A PARTICLE-LADEN CIRCULAR JET USING ELLIPTIC CO-ANNULAR FLOW: A MEANS FOR IMPROVING UTILIZATION AND EMISSION REDUCTIONS IN PULVERIZED COAL BURNER

    Energy Technology Data Exchange (ETDEWEB)

    Ahsan R. Choudhuri

    2003-06-01

    A passive control technology utilizing elliptic co-flow to control the particle flinging and particle dispersion in a particle (coal)-laden flow was investigated using experimental and numerical techniques. Preferential concentration of particles occurs in particle-laden jets used in pulverized coal burner and causes uncontrollable NO{sub x} formation due to inhomogeneous local stoichiometry. This particular project was aimed at characterizing the near-field flow behavior of elliptic coaxial jets. The knowledge gained from the project will serve as the basis of further investigation on fluid-particle interactions in an asymmetric coaxial jet flow-field and thus is important to improve the design of pulverized coal burners where non-homogeneity of particle concentration causes increased NO{sub x} formation.

  6. Characteristics of concentrated flow hydraulics for rangeland ecosystems: implications for hydrologic modeling

    Science.gov (United States)

    Concentrated flow is often the dominant source of water erosion following disturbance on rangeland. Because of the lack of studies that explain the hydraulics of concentrated flow on rangelands, cropland-based equations have typically been used for rangeland hydrology and erosion modeling, leading t...

  7. Effects of argon gas flow rate and guide shell on oxygen concentration in Czochralski silicon growth

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    φ200 mm silicon single crystals were grown in the φ450 mm hot zone of a Czochralski (CZ) furnace. By modifying the pattern and the velocity of the argon flow, the silicon single crystals with different oxygen concentrations were obtained. Through numerical simulation, the velocity of the argon gas flow was plotted for the first time. The experiment results were analyzed and the optimum condition of the argon flow with the lowest oxygen concentration was obtained.

  8. Study on High Temperature Regions of Annular Flame Tube and Flow Field of Near Wall Regions%火焰筒壁高温区与近壁区流场的数值模拟研究

    Institute of Scientific and Technical Information of China (English)

    杨芳芳; 吉洪湖; 郑妹; 张勃; 胡娅萍

    2012-01-01

    航空发动机火焰筒的大孔包括主燃孔和掺混孔,将多斜孔壁冷却方式应用到真实环形燃烧室的火焰筒壁上,运用CFD软件,通过数值模拟的方式,计算研究整个燃烧室的温度分布,特别考虑了火焰筒壁温的分布,对近壁区的流场进行计算研究.研究分析表明:内外环壁热侧大部分区域温度都保持在1 000 K~1 100K,在材料的长期许用温度范围内;同时针对外环壁主燃孔和掺混孔附近的局部高温点,提出冷却方案,改善了近壁区的流场分布,对改善高温点起到了很好的效果,最大幅度降低达13.2%,壁面温度更加均匀,对降低热应力水平,延长火焰筒使用寿命有利.%The big holes of Aero- engine combustor liner include primary holes and dilution holes,this paper applied the effusion- cooling method into the real annular flame tube. With the help of the CFD software , numerical simulation was carried out to investigate on the temperature distribution of the whole combustor, especially of the liners, including flow fields of near wall regions. The result shows that the temperature of most regions of outer and inner liners on the hot side is from 1 000 K to 1 100 K,which is in the material's long- term allowable temperature range. And cooling scheme was put forward considered on hot spots behind the primary holes and dilution holes on the outer liner, which changed the flow of the near wall regions,and effectively improved the hot spots. The most decreasing range of the highest temperature is 13.2% ,and more uniform wall temperature makes thermal stress level reduced and the service life of flame tubes extended.

  9. Gravel Accumulation in Deposits of Viscous Debris Flows with Hyper-concentration

    Institute of Scientific and Technical Information of China (English)

    WANG Yuyi; TAN Rongzhi; JAN Chyandeng; TIAN Bing

    2009-01-01

    According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types: high-viscous, viscous, and sub-viscous debris flows. Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio. This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied. The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.

  10. LED controlled flow photolysis for concentration gradients in microfluidic systems.

    Science.gov (United States)

    Potter, Oscar G; Thomas, Mark E; Breadmore, Michael C; Hilder, Emily F

    2010-05-21

    Many of the channels and reservoirs in microfluidic systems are used simply to allow liquids with different compositions to be delivered to where they are needed. An alternative approach is to use dissolved photochemicals and variable intensity LEDs to generate composition changes in situ. We applied this approach to generate concentration gradients of HCl for gradient ion chromatography.

  11. A review of concentrated flow erosion processes on rangelands: Fundamental understanding and knowledge gaps

    Directory of Open Access Journals (Sweden)

    Sayjro K. Nouwakpo

    2016-06-01

    Full Text Available Concentrated flow erosion processes are distinguished from splash and sheetflow processes in their enhanced ability to mobilize and transport large amounts of soil, water and dissolved elements. On rangelands, soil, nutrients and water are scarce and only narrow margins of resource losses are tolerable before crossing the sustainability threshold. In these ecosystems, concentrated flow processes are perceived as indicators of degradation and often warrant the implementation of mitigation strategies. Nevertheless, this negative perception of concentrated flow processes may conflict with the need to improve understanding of the role of these transport vessels in redistributing water, soil and nutrients along the rangeland hillslope. Vegetation influences the development and erosion of concentrated flowpaths and has been the primary factor used to control and mitigate erosion on rangelands. At the ecohydrologic level, vegetation and concentrated flow pathways are engaged in a feedback relationship, the understanding of which might help improve rangeland management and restoration strategies. In this paper, we review published literature on experimental and conceptual research pertaining to concentrated flow processes on rangelands to: (1 present the fundamental science underpinning concentrated flow erosion modeling in these landscapes, (2 discuss the influence of vegetation on these erosion processes, (3 evaluate the contribution of concentrated flow erosion to overall sediment budget and (4 identify knowledge gaps.

  12. Fluid-Structure Interaction Analysis on Turbulent Annular Seals of Centrifugal Pumps during Transient Process

    Directory of Open Access Journals (Sweden)

    Qinglei Jiang

    2011-01-01

    Full Text Available The current paper studies the influence of annular seal flow on the transient response of centrifugal pump rotors during the start-up period. A single rotor system and three states of annular seal flow were modeled. These models were solved using numerical integration and finite difference methods. A fluid-structure interaction method was developed. In each time step one of the three annular seal models was chosen to simulate the annular seal flow according to the state of rotor systems. The objective was to obtain a transient response of rotor systems under the influence of fluid-induced forces generated by annular seal flow. This method overcomes some shortcomings of the traditional FSI method by improving the data transfer process between two domains. Calculated results were in good agreement with the experimental results. The annular seal was shown to have a supportive effect on rotor systems. Furthermore, decreasing the seal clearance would enhance this supportive effect. In the transient process, vibration amplitude and critical speed largely changed when the acceleration of the rotor system increased.

  13. Multiple sample flow through immunomagnetic separator for concentrating pathogenic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Rotariu, Ovidiu [School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen (United Kingdom); Ogden, Iain D [Department of Medical Microbiology, University of Aberdeen, Aberdeen (United Kingdom); MacRae, Marion [Department of Medical Microbiology, University of Aberdeen, Aberdeen (United Kingdom); Udrea, Laura Elena [National Institute of R-D for Technical Physics I.F.T. Iasi, Mangeron 47 Blvd., Iasi (Romania); Strachan, Norval J C [School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen (United Kingdom)

    2005-06-21

    The standard method of immunomagnetic separation for isolating pathogenic bacteria from food and environmental matrices processes 1 ml volumes. Pathogens present at low levels (<0.5 pathogenic bacteria/g) will not be consistently detected by this method. Here a multiple sample flow through immunomagnetic separator has been designed and tested to process large volume samples (50 to 250 ml). Preliminary results show >97% recovery of polydisperse magnetic particles (diameter range 1 to 8 {mu}m) containing 29-33% w/w Fe{sub 3}O{sub 4} content. Between 70 and 130 times more of the pathogenic bacteria Escherichia coli O157 is recovered from PBS compared with the standard 1 ml method. Also, the recovery of E. coli O157 from beef mince homogenates, after a 4 h incubation at 42 deg. C, is between 80 and 180 times higher than the standard 1 ml method.

  14. Assessment of Average Tracer Concentration Approach for Flow Rate Measurement and Field Calibration

    Directory of Open Access Journals (Sweden)

    P. Sidauruk

    2015-12-01

    Full Text Available Tracer method is one of the methods available for open channel flow rate measurements such as in irrigation canals. Average tracer concentration approach is an instantaneous injection method that based on the average tracer concentrations value at the sampling point. If the procedures are correct and scientific considerations are justified, tracer method will give relatively high accuracy of measurements. The accuracy of the average tracer concentration approach has been assessed both in laboratory and field. The results of accuracy tests of open channel flow that has been conducted at the Center for Application Isotopes and Radiation Laboratory-BATAN showed that the accuracy level of average concentrations approach method was higher than 90% compared to the true value (volumetric flow rate. The accuracy of average tracer concentration approach was also assessed during the application of the method to measure flow rate of Mrican irrigation canals as an effort to perform field calibration of existing weirs. Both average tracer concentration approach and weirs can predict the trend of the flow correctly. However, it was observed that flow discrepancies between weirs measurement and average tracer concentration approach predictions were as high as 27%. The discrepancies might be due to the downgrading performances of the weirs because of previous floods and high sediment contents of the flow

  15. Comparison of whole saliva flow rates and mucin concentrations in healthy Caucasian young and aged adults.

    Science.gov (United States)

    Navazesh, M; Mulligan, R A; Kipnis, V; Denny, P A; Denny, P C

    1992-06-01

    Unstimulated and chewing-stimulated whole saliva samples were obtained from 42 healthy Caucasians; 21 were between 18 and 35 years of age, and 21 between 65 and 83 years of age. The unstimulated salivary flow rate was significantly lower in the aged group, but the stimulated flow rate was significantly higher in the aged than in the young group. Both groups showed significantly increased flow during salivary stimulation. MG1 and MG2 concentrations in unstimulated and stimulated saliva samples were significantly lower in the aged group. There were no significant correlations between salivary flow rates and MG1 and MG2 concentrations.

  16. Techniques to measure volumetric flow and particulate concentration in stacks with cyclonic flow

    Science.gov (United States)

    Sterrett, J. D.; Barbin, A. R.; Reece, J. W.; Carter, W. G.; Ferguson, B. B.

    1982-08-01

    It was determined that an in stack venturi can accurately measure volumetric flow in stacks with a severe cyclonic flow profile. The design requirements of the venturi are described. Also described was a low head loss, egg crate shaped device that effectively straightens cyclonic flow. Installation of such a device after a tangential inlet to a tall stack can result in considerable energy savings because it takes less fan power to push the straightened flow. Results to determine the particulate distribution downstream of the egg crate were inconclusive.

  17. Experimental Study on Convective Boiling Heat Transfer in Vertical Narrow Gap Annular Tube

    Institute of Scientific and Technical Information of China (English)

    Li Bin; He Anding; Wang Yueshe; Zhou Fangde

    2001-01-01

    Experiments are conducted to investigate the characteristics of single-phase forced-flow convection and boiling heat transfer of R113 flowing through annular tube with gap of 1, 1.5 and 2.5 mm, and also the visualization test are carried out to get two-phase flow regime. The data show that the Nusselt numbers for the narrow-gap are higher than those predicted by traditional large channel correlation and boiling heat transfer is enhanced. Based on the data obtained in this investigation, correlations for single-phase, forced convection and flow boiling in annular tube of different gap size has been developed.

  18. Hydraulic forces caused by annular pressure seals in centrifugal pumps

    Science.gov (United States)

    Iino, T.; Kaneko, H.

    1980-01-01

    The hydraulic forces caused by annular pressure seals were investigated. The measured inlet and exit loss coefficients of the flow through the seals were much smaller than the conventional values. The results indicate that the damping coefficient and the inertia coefficient of the fluid film in the seal are not affected much by the rotational speed or the eccentricity of the rotor, though the stiffness coefficient seemed to be influenced by the eccentricity.

  19. Cultivation of Spirulina maxima in an annular photochemical reactor

    Energy Technology Data Exchange (ETDEWEB)

    Leduy, A.; Therien, N.

    1979-08-01

    An 8-L annular photochemical reactor has been designed and built for the cultivation of micro- or semi-microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO/sub 2/ and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue-green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day/sup -1/, the optimal productivity was 0.91 g/L-day for biomass or 0.55 g/L-day for protein. This is equivalent to 14.5 g/m/sup 2/-day for biomass or 8.7 g/m/sup 2/-day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.

  20. Point and planar LIF for velocity-concentration correlations in a jet in cross flow

    DEFF Research Database (Denmark)

    Meyer, Knud Erik; Özcan, Oktay; Larsen, Poul Scheel

    2002-01-01

    (LDA). The flow considered is the mixing of a jet in a fully developed cross flow in a square duct with a width of 10 jet diameters. Both a laminar flow case, Re=675, and a turbulent flow case, Re=33750, are presented . For both flows, the ratio jet-to-duct mean velocities was R=3.3. Result of mean...... velocities, mean concentration and Reynolds fluxes in the symmetry plane of the jet are presented for PIV and PLIF measurements. The LIF measurements performed with the LDA equipment was in general in good agreement with the PIV/PLIF measurements. The cross sections selected for comparison are challenging...

  1. A Reconfigurable Radiation Pattern Annular Slot Antenna

    OpenAIRE

    Aziz, NA; Radhi, A; Nilavalan, R

    2016-01-01

    This paper contemplate a theoretical analysis of a pattern reconfigurable antenna using annular slot antenna operating in low frequency. A shorting pin is inserted to allow the annular slot antenna to have an omnidirectional radiation pattern like a monopole antenna. The reconfigurable antenna consists of numerous metal cylinders arranged around the annular slot antenna. By controlling pin diodes associated with the metal cylinders, the antenna is capable of working up in different dire...

  2. KINETIC MODELING OF CONSTITUTIVE RELATIONS FOR PARTICLE MOTION IN LOW TO MODERATELY CONCENTRATED FLOWS

    Institute of Scientific and Technical Information of China (English)

    Guangqian WANG; Xudong FU; Xingkui WANG

    2005-01-01

    Formulating underlying mechanisms of concentrated solid-liquid flows is essential for simulation of various industrial processes and natural phenomena. A generalized constitutive model for particle motion in flows with low to moderate solids concentrations is developed. This generalized model facilitates characterization of inelastic collisions, particle-fluid interactions, and shearing effects.Moderately concentrated simple shear flows of a sand-water mixture are analyzed, and comparisons of model predictions and experimental data are in good agreement. This model exhibits sound performance in characterizing particle motion for wide ranges of concentration and shear rate, and may supply a reasonable and competent alternative to previous models developed for dilute and rapid-granular flows when applied to moderately concentrated situations. The concentration approaches zero (C → 0) asymptote is observed at a relatively high shear rate in model predictions.Assumption of low collisional dissipation of the particle phase as C → 0 is more reasonable for this observation, compared to that without the interstitial fluid effect. Accurately modeling energy dissipation is important for characterizing the stability of dilute simple shear flows of solid-liquid mixtures. Incorporating friction forces will also facilitate improvement of the applicability of this generalized model to flows at extremely high concentrations.

  3. Modeling flow for modified concentric cylinder rheometer geometry

    Science.gov (United States)

    Ekeruche, Karen; Connelly, Kelly; Kavehpour, H. Pirouz

    2016-11-01

    Rheology experiments on biological fluids can be difficult when samples are limited in volume, sensitive to degradation, and delicate to extract from tissues. A probe-like geometry has been developed to perform shear creep experiments on biological fluids and to use the creep response to characterize fluid material properties. This probe geometry is a modified concentric cylinder setup, where the gap is large and we assume the inner cylinder rotates in an infinite fluid. To validate this assumption we perform shear creep tests with the designed probe on Newtonian and non-Newtonian fluids and vary the outer cylinder container diameter. We have also created a numerical model based on the probe geometry setup to compare with experimental results at different outer cylinder diameters. A creep test is modeled by applying rotation to the inner cylinder and solving for the deformation of the fluid throughout the gap. Steady state viscosity values are calculated from creep compliance curves and compared between experimental and numerical results.

  4. Calculation of watershed flow concentration based on the grid drop concept

    Directory of Open Access Journals (Sweden)

    Rui Xiaofang

    2008-03-01

    Full Text Available The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershed are obtained using a digital elevation model (DEM. Regarding the slope as an uneven carpet through which the grid drop passes, a formula for overland flow velocity differing from Manning’s formula for stream flow as well as Darcy's formula for pore flow is proposed. Compared with the commonly used unit hydrograph and isochronal methods, this new methodology has outstanding advantages in that it considers the influences of the slope velocity field and the heterogeneity of spatial distribution of rainfall on the flow concentration process, and includes only one parameter that needs to be calibrated. This method can also be effectively applied to the prediction of hydrologic processes in un-gauged basins.

  5. Calculation of watershed flow concentration based on the grid drop concept

    Institute of Scientific and Technical Information of China (English)

    Rui Xiaofang; Yu Mei; Liu Fanggui; Gong Xinglong

    2008-01-01

    The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershed are obtained using a digital elevation model (DEM). Regarding the slope as an uneven carpet through which the grid drop passes, a formula for overland flow velocity differing from Manning's formula for stream flow as well as Darcy's formula for pore flow is proposed. Compared with the commonly used unit hydrograph and isochronal methods, this new methodology has outstanding advantages in that it considers the influences of the slope velocity field and the heterogeneity of spatial distribution of rainfall on the flow concentration process, and includes only one parameter that needs to be calibrated. This method can also be effectively applied to the prediction of hydrologic processes in un-gauged basins.

  6. analysis of flow in a concentric annulus using finite element method

    African Journals Online (AJOL)

    user

    ABSTRACT. This work presents the computational modelling of the velocity distribution of an incompressible fluid flowing in a ... concentric annulus with center body rotation. [9] used .... pipe at a glance with a very high accuracy compared to.

  7. Shear-induced particle diffusion and its effects on the flow of concentrated suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Acrivos, A. [City College of CUNY, New York, NY (United States)

    1996-12-31

    The mechanism underlying shear-induced particle diffusion in concentrated suspensions is clarified. Examples are then presented where this diffusion process plays a crucial role in determining the manner by which such suspensions flow under laminar conditions.

  8. Simulation and validation of concentrated subsurface lateral flow paths in an agricultural landscape

    Directory of Open Access Journals (Sweden)

    Q. Zhu

    2009-08-01

    Full Text Available The importance of soil water flow paths to the transport of nutrients and contaminants has long been recognized. However, effective means of detecting concentrated subsurface flow paths in a large landscape are still lacking. The flow direction and accumulation algorithm based on single-direction flow algorithm (D8 in GIS hydrologic modeling is a cost-effective way to simulate potential concentrated flow paths over a large area once relevant data are collected. This study tested the D8 algorithm for simulating concentrated lateral flow paths at three interfaces in soil profiles in a 19.5-ha agricultural landscape in central Pennsylvania, USA. These interfaces were (1 the interface between surface plowed layers of Ap1 and Ap2 horizons, (2 the interface with subsoil water-restricting clay layer where clay content increased to over 40%, and (3 the soil-bedrock interface. The simulated flow paths were validated through soil hydrologic monitoring, geophysical surveys, and observable soil morphological features. The results confirmed that concentrated subsurface lateral flow occurred at the interfaces with the clay layer and the underlying bedrock. At these two interfaces, the soils on the simulated flow paths were closer to saturation and showed more temporally unstable moisture dynamics than those off the simulated flow paths. Apparent electrical conductivity in the soil on the simulated flow paths was elevated and temporally unstable as compared to those outside the simulated paths. The soil cores collected from the simulated flow paths showed significantly higher Mn content at these interfaces than those away from the simulated paths. These results suggest that (1 the D8 algorithm is useful in simulating possible concentrated subsurface lateral flow paths if used with appropriate threshold value of contributing area and sufficiently detailed digital elevation model (DEM; (2 repeated electromagnetic surveys can reflect the temporal change of soil

  9. Impulsively started, steady and pulsated annular inflows

    Science.gov (United States)

    Abdel-Raouf, Emad; Sharif, Muhammad A. R.; Baker, John

    2017-04-01

    A computational investigation was carried out on low Reynolds number laminar inflow starting annular jets using multiple blocking ratios and atmospheric ambient conditions. The jet exit velocity conditions are imposed as steady, unit pulsed, and sinusoidal pulsed while the jet surroundings and the far-field jet inlet upstream conditions are left atmospheric. The reason is to examine the flow behavior in and around the jet inlet under these conditions. The pulsation mode behavior is analyzed based on the resultant of the momentum and pressure forces at the entry of the annulus, the circulation and vortex formation, and the propulsion efficiency of the inflow jets. The results show that under certain conditions, the net force of inflow jets (sinusoidal pulsed jets in particular) could point opposite to the flow direction due to the adverse pressure drops in the flow. The propulsion efficiency is also found to increase with pulsation frequency and the sinusoidal pulsed inflow jets are more efficient than the unit pulsed inflow jets. In addition, steady inflow jets did not trigger the formation of vortices, while unit and sinusoidal pulsed inflow jets triggered the formation of vortices under a certain range of frequencies.

  10. The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

    KAUST Repository

    Elbaz, Ayman M.

    2015-08-29

    The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

  11. Energy efficiency of a concentration gradient flow battery at elevated temperatures

    NARCIS (Netherlands)

    Egmond, van W.J.; Starke, U.K.; Saakes, M.; Buisman, C.J.N.; Hamelers, H.V.M.

    2017-01-01

    Fast growth of intermittent renewable energy generation introduces a need for large scale electricity storage. The Concentration Gradient Flow Battery (CGFB) is an emerging technology which combines Electrodialysis with Reverse Electrodialysis into a flow battery which is able to safely store

  12. Optimal design of bodies of revolution of annular jet flow surface and analysis of the drag reduction mechanism%旋成体环形射流表面优化设计与减阻机理分析

    Institute of Scientific and Technical Information of China (English)

    赵刚; 李芳; 臧东阳

    2014-01-01

    With a focus on the problem of bionic jet drag reduction , a bionic jet surface model is presented by using the jet flow of shark cheeks as the prototype .Based on the orthogonal test design method , this paper goes into detail about numerical simulations by making a comparison between bodies of revolution of a bionic annular jet flow sur -face ( BRBAJFS ) and smooth bodies of revolution with the SST k-ωturbulence model .The results prove that BRBAJFS has obvious drag-reduction and energy-saving effects .The highest energy saving efficiency can be 262 and the corresponding rate of drag reduction is 27.74%.The jet velocity has the most important impact on energy saving efficiency and it has a linear relation with the energy saving efficiency , i.e., the energy saving efficiency will decrease with an increase in the jet velocity .Furthermore, the position of the jet hole has the greatest impact on the total resistance .When the jet hole is far away from the bottom of the bodies of revolution , the drag reduction effi-ciency will increase and BRBAJFS decreases the viscous friction resistance by decreasing the velocity gradient of the wall and increasing the area of counterblows .There can also be a decrease in the pressure drag resulting from the jet fluid complementing the bottom of the bodies of revolution fluid .%针对仿生射流表面减阻问题,以鲨鱼鳃部射流为原型,建立仿生射流表面模型,采用正交试验设计法,利用SST k-ω湍流模型对仿生环形射流表面旋成体与光滑旋成体进行数值模拟。结果表明:旋成体环形射流表面具有减阻节能效果,最高节能效率达262,此时的减阻率为27.74%;射流速度对节能效率影响最大,射流速度与节能效率呈线性关系,随着射流速度增大,节能效率减小,射流孔位置对总阻力的影响最大,随着射流孔远离旋成体底部,减阻率增大。旋成体环形射流表面通过减小壁面的速度梯

  13. Production of annular flat-topped vortex beams

    Institute of Scientific and Technical Information of China (English)

    Jiannong Chen; Yongjiang Yu; Feifei Wang

    2011-01-01

    @@ A model of an annular flat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.%A model of an annular fiat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.

  14. Bacterial Concentration and Diversity within Repetitive Aliquots Collected from Replicate Continuous-Flow Bioreactor Cultures.

    Science.gov (United States)

    Crippen, Tawni L; Sheffield, Cynthia L; Andrews, Kathleen; Bongaerts, Roy; Nisbet, David J

    2008-01-01

    The aim of this study was to determine the reproducibility of small volume repeat sampling from replicate bioreactors with stabilized continuous-flow chicken cecal bacterial communities. Bacterial concentration and diversity were analyzed by phenotypic, biochemical and ribotype analysis. Significant differences in concentrations and variations in diversity were found in replicate bioreactors.

  15. Concentration Dependence of VO2+ Crossover of Nafion for Vanadium Redox Flow Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, Jamie [University of Tennessee, Knoxville (UTK); Jones, Amanda [University of Tennessee, Knoxville (UTK); Zawodzinski, Thomas A [ORNL

    2013-01-01

    The VO2+ crossover, or permeability, through Nafion in a vanadium redox flow battery (VRFB) was monitored as a function of sulfuric acid concentration and VO2+ concentration. A vanadium rich solution was flowed on one side of the membrane through a flow field while symmetrically on the other side a blank or vanadium deficit solution was flowed. The blank solution was flowed through an electron paramagnetic resonance (EPR) cavity and the VO2+ concentration was determined from the intensity of the EPR signal. Concentration values were fit using a solution of Fick s law that allows for the effect of concentration change on the vanadium rich side. The fits resulted in permeability values of VO2+ ions across the membrane. Viscosity measurements of many VO2+ and H2SO4 solutions were made at 30 60 C. These viscosity values were then used to determine the effect of the viscosity of the flowing solution on the permeability of the ion. 2013 The Electrochemical Society. [DOI: 10.1149/2.004306jes] All rights reserved.

  16. TWO-PHASE FLOW OF HIGHLY CONCENTRATED SLURRY IN A PIPELINE

    Institute of Scientific and Technical Information of China (English)

    NI Fu-sheng; ZHAO Li-juan; MATOUSEK V.; VLASBLOM W. J.; ZWARTBOL A.

    2004-01-01

    Hydraulic transport of sand is one of the key processes in river, lake, harbor and waterway dredging engineering. Understanding the flow resistance, solid distribution, flow stratification, transport economy, etc., in the two-phase flow of sand-water mixture through a pipeline is crucial to the design and operation of power drives of a dredger, and to the construction of a dredging project. This paper presents the intensive laboratory experimental data and physical and numerical analyses on the highly concentrated slurry flow under an extended large range of slurry mean velocities for three narrow-graded sands of different sizes. The investigation indicates that the solids concentration and particle size strongly affect the slurry flow characteristics.

  17. Soliton bunching in annular Josephson junctions

    DEFF Research Database (Denmark)

    Vernik, I.V; Lazarides, Nickos; Sørensen, Mads Peter

    1996-01-01

    By studying soliton (fluxon) motion in long annular Josephson junctions it is possible to avoid the influence of the boundaries and soliton-soliton collisions present in linear junctions. A new experimental design consisting of a niobium coil placed on top of an annular junction has been used...

  18. Comparison between a steady-state and a transient flow model and related radionuclide concentration predictions

    Science.gov (United States)

    Gedeon, M.; Mallants, D.

    2012-04-01

    Radionuclide concentration predictions in aquifers play an important role in estimating impact of planned surface disposal of radioactive waste in Belgium, developed by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF), who also coordinates and leads the corresponding research. Long-term concentration predictions are based on a steady-state flow solution obtained by a cascade of multi-scale models from the catchment to the detailed (site) scale performed in MODFLOW. To test the concept and accuracy of the groundwater flow solution and conservativeness of the concentration predictions obtained therewith, a transient model, considered more realistic, was set up in a sub-domain of the intermediate scale steady-state model. Besides the modelling domain reduction, the transient model was and exact copy of the steady-state model, having the infiltration as the only time-varying parameter. The transient model was run for a twenty-year period, whereas the results were compared to the steady-state results based on infiltration value and observations averaged over the same period. The comparison of the steady-state and transient flow solutions includes the analyses of the goodness of fit, the parameter sensitivities, relative importance of the individual observations and one-percent sensitivity maps. The steady-state and transient flow solutions were subsequently translated into a site-scale transport model, used to predict the radionuclide concentrations in a hypothetical well in the aquifers. The translation of the flow solutions between the models of distinct scales was performed using the Local grid refinement method available in MODFLOW. In the site-scale models, MT3DMS transport simulations were performed to obtain respective concentration predictions in a hypothetical well, situated at 70 meters from the disposal tumuli. The equilibrium concentrations based on a constant source flux achieved using a steady-state solution were then

  19. Energy harvesting through charged nanochannels using external flows of different salt concentrations

    Science.gov (United States)

    Chanda, Sourayon; Tsai, Peichun Amy

    2016-11-01

    Renewable electricity may be generated by mixing of two solutions of different salt concentrations through charged nanochannels or pores, by leveraging ion-selective effect of the nano-confinements. We numerically investigate such a continuous power generation system using reverse electrodialysis (RED) with external flows. In the simulation model, two reservoirs are connected using a nanochannel of constant surface charge density. Solutions of high and low concentrations flow through the two reservoirs at a constant velocity. We examine the effects of (salt) concentration gradients and nanochannel dimensions on the power generation. Moreover, the effect of external flow velocity on the process is analyzed. Our results show that the maximum surface charge density, open circuit voltage, channel resistance, and energy conversion efficiency of the process are significantly affected by the difference of the high and low concentrations and the nanochannel dimension ratio.

  20. [Generalized granuloma annulare or diffuse dermal histiocytosis?].

    Science.gov (United States)

    Kretzschmar, L; Biel, K; Luger, T A; Goerdt, S

    1995-08-01

    Generalized granuloma annulare is a rare variant of granuloma annulare affecting the trunk and extremities with a multitude of lesions. In contrast to localized granuloma annulare, generalized granuloma annulare occurs in older patients, shows a stronger association with diabetes, and is characteristically chronic. Like our 55-year-old patient, most patients present with papules and annular plaques; less often, macular or non-annular lesions may be encountered. Histology often fails to show necrobiotic or necrotic connective tissue changes demarcated by a palisading granuloma. Instead, there are diffuse dermal, band-like or nodular aggregations of histiocytes intermingled with some multinucleated giant cells and a predominantly lymphocytic infiltrate in the periphery. Because of its special characteristics, it has been suggested that generalized granuloma annulare might constitute a separate disease entity and that it should be classed among the primary cutaneous histiocytoses as a diffuse dermal histiocytosis. Using immunohistochemistry to determine the macrophage phenotype of the lesional histiocytes, we have shown that generalized granuloma annulare is not a cutaneous histiocytosis. Neither MS-1 high-molecular-weight protein, a new specific marker for cutaneous non-Langerhans cell histiocytoses, nor CD1a, the well-known marker for Langerhans cells and Langerhans cell histiocytoses, is expressed by the lesional histiocytes of our patient. In contrast, the antigen expression pattern was diagnostic for non-infectious granulomas and was highly similar to that in localized granuloma annulare. In contrast to the successful treatment of localized granuloma annulare reported with intralesional interferon beta-1, systemic treatment with interferon alpha-2b (9 x 10(6) units three times a week) was ineffective.

  1. Modeling and Numerical Simulation of Yield Viscoplastic Fluid Flow in Concentric and Eccentric Annuli

    Institute of Scientific and Technical Information of China (English)

    毛在砂; 杨超; Vassilios C. Kelessidis

    2012-01-01

    Numerical solution of yield viscoplastic fluid flow is hindered by the singularity inherent to the Herschel-Bulkley model. A finite difference method over the boundary-fitted orthogonal coordinate system is util- ized to investigate numerically the fully developed steady flow of non-Newtonian yield viscoplastic fluid through concentric and eccentric annuli. The fluid rheology is described with the Herschel-Bulkley model. The numerical simulation based on a continuous viscoplastic approach to the Herschel-Bulkley model is found in poor accordance with the experimental data on volumetric flow rate of a bentonite suspension. A strict mathematical model for Herschel-Bulkley fluid flow is established and the corresponding numerical procedures are proposed. However, only the case of flow of a Herschel-Bulkley fluid in a concentric annulus is resolved based on the presumed flow stnicture by using the common optimization technique. Possible flow structures in an eccentric afinulus are presumed, and further challenges in numerical simulation of the Herschel-Bulkley fluid flow are suggested.

  2. Simulations of Flow Circulations and Atrazine Concentrations in a Midwest U.S. Reservoir

    Science.gov (United States)

    Zhao, Xianggui; Gu, Roy R.; Guo, Chuling; Wang, Kui; Li, Shijie

    Atrazine is the most commonly used herbicide in the spring for pre-emergent weed control in the corn cropping area in the Midwestern United States. A frequent high level of herbicide concentrations in reservoirs is a great concern for public health and aquatic ecosystems. In this study, a two-dimensional hydrodynamics and toxic contaminant transport model was applied to Saylorville Reservoir, Iowa, USA. The model simulates physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. Model results were validated by measured temperatures and atrazine concentrations. Simulated flow velocities, water temperatures, and chemical concentrations demonstrated that the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation patterns in the reservoir. In particular, the simulated fate and transport of atrazine showed the effect of flow circulation on spatial distribution of atrazine during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A thorough understanding of the fate and transport of atrazine in the reservoir can assist in developing operation and pollution prevention strategies with respect to timing, amount, and depth of withdrawal. The responses of atrazine transport to various boundary conditions provide useful information in assessing environmental impact of alternative upstream watershed management practices on the quality of reservoir water.

  3. Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

    Science.gov (United States)

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

    2017-07-01

    Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

  4. BIAS ERRORS INDUCED BY CONCENTRATION GRADIENT IN SEDIMENT-LADEN FLOW MEASUREMENT WITH PTV

    Institute of Scientific and Technical Information of China (English)

    LI Dan-xun; LIN Qiu-sheng; ZHONG Qiang; WANG Xing-kui

    2012-01-01

    Sediment-laden flow measurement with Particle Tracking Velocimetry (PTV) introduces a series of finite-sized sampling bins along the vertical of the flow.Instantaneous velocities are collected at each bin and a significantly large sample is established to evaluate mean and root mean square (rms) velocities of the flow.Due to the presence of concentration gradient,the established sample for the solid phase inv(o)lves more data from the lower part of the sampling bin than from the upper part.The concentration effect causes bias errors in the measured mean and rms velocities when velocity varies across the bin.These bias errors are analytically quantified in this study based on simplified linear velocity and concentration distributions.Typical bulk flow characteristics from sediment-laden flow measurements are used to demonstrate rough estimation of the error magnitude.Results indicate that the mean velocity is underestimated while the rms velocity is overestimated in the ensemble-averaged measurement.The extent of deviation is commensurate with the bin size and the rate of concentration gradient.Procedures are proposed to assist determining an appropriate sampling bin size in certain error limits.

  5. The concentration of the large-scale solar magnetic field by a meridional surface flow

    Science.gov (United States)

    Devore, C. R.; Boris, J. P.; Sheeley, N. R., Jr.

    1984-01-01

    Analytical and numerical solutions to the magnetic flux transport equation in the absence of new bipolar sources of flux are calculated for several meridional flow profiles and a range of peak flow speeds. It is found that a poleward flow with a broad profile and a nominal 10 m/s maximum speed concentrates the large-scale field into very small caps of less than 15 deg half-angle, with average field strengths of several tens of gauss, contrary to observations. A flow which reaches its peak speed at a relatively low latitude and then decreases rapidly to zero at higher latitudes leads to a large-scale field pattern which is consistent with observations. For such a flow, only lower latitude sunspot groups can contribute to interhemispheric flux annihilation and the resulting decay and reversal of the polar magnetic fields.

  6. On the peculiarities of LDA method in two-phase flows with high concentrations of particles

    Science.gov (United States)

    Poplavski, S. V.; Boiko, V. M.; Nesterov, A. U.

    2016-10-01

    Popular applications of laser Doppler anemometry (LDA) in gas dynamics are reviewed. It is shown that the most popular method cannot be used in supersonic flows and two-phase flows with high concentrations of particles. A new approach to implementation of the known LDA method based on direct spectral analysis, which offers better prospects for such problems, is presented. It is demonstrated that the method is suitable for gas-liquid jets. Owing to the progress in laser engineering, digital recording of spectra, and computer processing of data, the method is implemented at a higher technical level and provides new prospects of diagnostics of high-velocity dense two-phase flows.

  7. Large concentration changes due to thermal diffusion effects in gas flow microsystems with temperature gradients

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Johannessen, Tue; Jensen, Søren;

    Thermal diffusion, or Sorét diffusion, is shown to cause significant concentration changes and transients in gas flow microsystems with temperature gradients. In a silicon microsystem, a temperature gradient of about 100 oC/mm is measured to produce concentration transients of up to 13.......7 % in an argon/helium mixture, when the flow is abruptly changed from a high value to a low value. Finite element simulations of the thermal diffusion in a geometry similar to the experimental setup reproduce the measurements....

  8. Domain-adaptive finite difference methods for collapsing annular liquid jets

    Science.gov (United States)

    Ramos, J. I.

    1993-01-01

    A domain-adaptive technique which maps a time-dependent, curvilinear geometry into a unit square is used to determine the steady state mass absorption rate and the collapse of annular liquid jets. A method of lines is used to solve the one-dimensional fluid dynamics equations written in weak conservation-law form, and upwind differences are employed to evaluate the axial convective fluxes. The unknown, time-dependent, axial location of the downstream boundary is determined from the solution of an ordinary differential equation which is nonlinearly coupled to the fluid dynamics and gas concentration equations. The equation for the gas concentration in the annular liquid jet is written in strong conservation-law form and solved by means of a method of lines at high Peclet numbers and a line Gauss-Seidel method at low Peclet numbers. The effects of the number of grid points along and across the annular jet, time step, and discretization of the radial convective fluxes on both the steady state mass absorption rate and the jet's collapse rate have been analyzed on staggered and non-staggered grids. The steady state mass absorption rate and the collapse of annular liquid jets are determined as a function of the Froude, Peclet and Weber numbers, annular jet's thickness-to-radius ratio at the nozzle exit, initial pressure difference across the annular jet, nozzle exit angle, temperature of the gas enclosed by the annular jet, pressure of the gas surrounding the jet, solubilities at the inner and outer interfaces of the annular jet, and gas concentration at the nozzle exit. It is shown that the steady state mass absorption rate is proportional to the inverse square root of the Peclet number except for low values of this parameter, and that the possible mathematical incompatibilities in the concentration field at the nozzle exit exert a great influence on the steady state mass absorption rate and on the jet collapse. It is also shown that the steady state mass absorption

  9. Use of flow cytometry and monochlorobimane to quantitate intracellular glutathione concentrations in feline leukocytes.

    Science.gov (United States)

    Webb, Craig; Bedwell, Cathy; Guth, Amanda; Avery, Paul; Dow, Steven

    2006-08-15

    Oxidative stress and abnormal glutathione metabolism is thought to play an important role in various diseases of cats. However, current assays for the reduced form of glutathione (GSH) are time-consuming and semi-quantitative and do not allow assessment of GSH concentrations in individual cell populations. Therefore, we developed a flow cytometric assay for rapid determination of intracellular GSH concentrations in feline blood leukocytes. The assay was based on the ability of the non-fluorescent substrate monochlorobimane (mBCl) to form fluorescent adducts with GSH in a reaction catalyzed by the enzyme glutathione-S-transferase. Using flow cytometry, we found that mBCl was sensitive and specific for intracellular detection of the reduced form of GSH in feline leukocytes. Intracellular GSH concentrations were also stable for at least 24h in EDTA preserved whole blood samples stored at 4 degrees C. Neutrophils and monocytes from normal cats had significantly higher intracellular concentrations of GSH than T cells and B cells. The effects of FIV infection on intracellular GSH concentrations in cats were assessed using flow cytometry. We found that neutrophils from FIV-infected cats had significantly increased GSH concentrations, whereas intracellular GSH concentrations were significantly decreased in CD4(+) and CD8(+) lymphocytes from FIV-infected cats, compared to age-matched control animals. We conclude that a flow cytometric assay based on mBCl may be used to accurately and rapidly assess the effects of various disease states and treatments on GSH concentration in cat leukocytes and to help assess intracellular oxidative stress.

  10. Solar cycle modulation of Southern Annular Mode

    Science.gov (United States)

    Kuroda, Yuhji

    2016-04-01

    Climate is known to be affected by various factors, including oceanic changes and volcanic eruptions. 11-year solar cycle change is one of such important factors. Observational analysis shows that the winter-mean North Atlantic Oscillation (NAO) and late-winter/spring Southern Annular Mode (SAM) show structural modulation associated with 11-year solar cycle. In fact, these signals tend to extend from surface to upper stratosphere and persistent longer period only in the High Solar (HS) years. In the present study, we used 35-year record of ERA-Interim reanalysis data and performed wave-energy and momentum analysis on the solar-cycle modulation of the SAM to examine key factors to create such solar-SAM relationship. It is found that enhanced wave-mean flow interaction tends to take place in the middle stratosphere in association with enhanced energy input from diabatic heating on September only in HS years. The result suggests atmospheric and solar conditions on September are keys to create solar-SAM relationship.

  11. Impingement of a radial jet with an annular jet. 3rd Report. Curved properties of main jet with pressure field; Hoshajo funryu to kanjo funryu no shototsu ni kansuru kenkyu. 3. Atsuryokuba ni yoru shufunryu no wankyoku tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, T.; Kozato, Y.; Tanaka, E. [Gifu University, Gifu (Japan). Faculty of Engineering; Kariya, M. [Meidensha Corp., Tokyo (Japan)

    1994-12-25

    Annular jets (control flows) flowing out from a columnar nozzle and a concentrically circular annular nozzle were impinged perpendicularly to a main jet flowing radially from the columnar nozzle. Then, an investigation was given on pressure in a recirculation flow region, bending of the main jet, and reattachment characteristics of the main jet onto a side wall face when the deflection of the main jet and its reattachment phenomenon onto the side wall face are controlled. The experiment was performed under the conditions of a nozzle width of 6 mm, an inter-nozzle distance of 4, a control flow rate (a ratio of a flow-out rate of the control flow to that of the main jet) from 0 to 0.6, with the step height varied. Investigations were made on change of static pressure distribution in jets in the downstream direction, change of static pressure on the side wall face in the downstream direction, and the relationship between the reattachment position on the side wall and the average static pressure in the recirculation flow region. The relationship of the reattachment position of the main jet on the side wall with the average side wall static pressure and the average static pressure in the recirculation flow region is expressed by one curve. The reattachment position gets closer to the nozzle outlet as the pressure decreases in the recirculation flow region. 9 refs., 14 figs., 1 tab.

  12. Divergent Field Annular Ion Engine Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed work investigates an approach that would allow an annular ion engine geometry to achieve ion beam currents approaching the Child-Langmuir limit. In this...

  13. A clinical study of annular cyclitis

    Directory of Open Access Journals (Sweden)

    Marilita Michael Moschos

    2009-02-01

    Full Text Available Marilita Michael Moschos1, Yan Guex-Crosier2, Ioannis Margetis1, Leonidas Zografos21Department of Ophthalmology, University of Athens, Greece; 2Jules Gonin Eye Hospital, University of Lausanne, SwitzerlandPurpose: To investigate six cases of annular cyclitis.Methods: All patients with impairment of visual acuity underwent complete ophthalmologic examination, color fundus photography, laboratory tests and fluorescein angiography. Indocyanine green (ICG angiography and B-scan ultrasonography were also performed in three cases in order to diagnose the disease.Results: All patients presented a unilateral or bilateral granulomatous uveitis, associated with inflammatory annular cyclitis. They had a shallow anterior chamber, a mildly elevated intraocular pressure (under 25 mm Hg and an annular serous retinal detachment. A resolution was observed after specific therapy associated with systemic prednisolone therapy and antiglaucomatous drops.Conclusion: This is the first description of an observational study of six patients with inflammatory annular cyclitis.Keywords: cyclitis, uveitis, malignant glaucoma

  14. CONTRIBUTION OF RADON FLOWS AND RADON SOURCES TO THE RADON CONCENTRATION IN A DWELLING

    NARCIS (Netherlands)

    DEMEIJER, RJ; STOOP, P; PUT, LW

    1992-01-01

    In this paper a model is presented for analysis of the radon concentrations in a compartment in terms of contributions from transport by flows of air between compartments and from radon sources in the compartment. Measurements were made to study the effect of increased natural ventilation of the cra

  15. Measurements of solids concentration and axial solids velocity in gas-solid two-phase flows.

    NARCIS (Netherlands)

    Nieuwland, J.J.; Meijer, R.; Kuipers, J.A.M.; Swaaij, van W.P.M.

    1996-01-01

    Several techniques reported in the literature for measuring solids concentration and solids velocity in (dense) gas-solid two-phase flow have been briefly reviewed. An optical measuring system, based on detection of light reflected by the suspended particles, has been developed to measure local soli

  16. Laboratory Investigation of Rill Erosion on Compost Blankets under Concentrated Flow Conditions

    Science.gov (United States)

    A flume study was conducted using a soil, yard waste compost, and an erosion control compost to investigate the response to concentrated flow and determine if the shear stress model could be used to describe the response. Yard waste compost (YWC) and the bare Cecil soil (CS) cont...

  17. Two methods for calculating regional cerebral blood flow from emission computed tomography of inert gas concentrations

    DEFF Research Database (Denmark)

    Kanno, I; Lassen, N A

    1979-01-01

    Two methods are described for calculation of regional cerebral blood flow from completed tomographic data of radioactive inert gas distribution in a slice of brain tissue. It is assumed that the tomographic picture gives the average inert gas concentration in each pixel over data collection periods...

  18. Sediment suspension in oscillatory flow: measurements of instantaneous concentration at high shear

    DEFF Research Database (Denmark)

    Staub, Carsten; Jonsson, Ivar G; Svendsen, Ib A.

    1996-01-01

    Different syphon type suspended load probes were used together with a specially developed ''carousel'' sampler for measurements of the instantaneous sediment concentration in turbulent oscillatory flow over a sand bed, Shields parameters were well above the ripple/flat bed transition region, resu...

  19. Laboratory Investigation of Rill Erosion on Compost Blankets under Concentrated Flow Conditions

    Science.gov (United States)

    A flume study was conducted using a soil, yard waste compost, and an erosion control compost to investigate the response to concentrated flow and determine if the shear stress model could be used to describe the response. Yard waste compost (YWC) and the bare Cecil soil (CS) cont...

  20. Entraining Flow of a Concentrated Benthic Suspension: Computations with the Prandtl Mixing-Length Model

    NARCIS (Netherlands)

    Kranenburg, C.

    1999-01-01

    The Prandtl mixing-length model of turbulent exchange of mass and momentum is applied to calculate the entrainment of overlying water into a layer of suspended fine sediment at a horizontal bed. In the field the flow and turbulence in such a concentrated benthic suspension (CBS) are driven by a

  1. Highly sensitive contactless conductivity microchips based on concentric electrodes for flow analysis.

    Science.gov (United States)

    Lima, Renato S; Piazzetta, Maria H O; Gobbi, Angelo L; Segato, Thiago P; Cabral, Murilo F; Machado, Sergio A S; Carrilho, Emanuel

    2013-12-18

    In this communication, we describe for the first time the integration of concentric electrodes (wrapping around the microchannel) in microchips. The use of such electrodes has been shown to be effective towards improvement of the sensitivity and detectability in pressure-driven flow platforms incorporating C(4)D.

  2. CONTRIBUTION OF RADON FLOWS AND RADON SOURCES TO THE RADON CONCENTRATION IN A DWELLING

    NARCIS (Netherlands)

    DEMEIJER, RJ; STOOP, P; PUT, LW

    1992-01-01

    In this paper a model is presented for analysis of the radon concentrations in a compartment in terms of contributions from transport by flows of air between compartments and from radon sources in the compartment. Measurements were made to study the effect of increased natural ventilation of the cra

  3. Numerical simulation of dissolved oxygen concentration in water flow over stepped spillways.

    Science.gov (United States)

    Cheng, Xiangju; Chen, Xuewei

    2013-05-01

    This study developed an improved Eulerian model for the simulation of an air-water flow field over stepped spillways. The improved drag model applied different drag coefficients for bubbles and for free surface flows or gas cavities. Void fraction and turbulence correction were used in determining the bubble drag coefficient. The calculated air entrainment and air-water velocity could be adapted using these parameters. With the improved drag model, the Eulerian simulations predicted the location of the inception point, the distributions of air void fraction, velocity distributions, and pressure distributions. The change in the dissolved oxygen (DO) concentration from upstream of the stepped spillways, to downstream, was simulated based on the improved computational fluid dynamics model and the transport equation for DO transferring. The numerical DO concentration coincided with the experimental results. Therefore, the improved CFD model and the numerical methods presented here can provide possible optimization tools for strong air entrainment flows.

  4. The Effect of Flow Distribution on the Concentration of NO Produced by Pulsed Arc Discharge

    Institute of Scientific and Technical Information of China (English)

    HU Hui; BAO Bin; WANG He-li; LIANG Hai-yan; HE Jun-jia; HE Zheng-hao; LI Jin

    2007-01-01

    As a new method to cure acute respiratory distress syndrome (ARDS),high blood pressure and some illnesses related to the lung,NO has recently received more attention.Thermal plasmas produced by arc discharge can create medical NO,but the concentration of NO2 produced by arc discharge must be controlled simultaneously.This paper investigates the characteristics and regulations of NO production at different flow distribution by pulsed arc discharge in dry air with a special pulsed power.The experimental results show that the flow distribution has a considerable effect on the NO concentration,the stabilization of NO.The production of NO2 could be controlled and the ratio of NO2/NO was decreased to about 10% in the arc discharge.Therefore,the arc discharge could produce stable inhaled NO for medical treatment by changing the flow distribution.

  5. Magnetic resonance imaging (MRI: a technique to study flow an microstructure of concentrated emulsions

    Directory of Open Access Journals (Sweden)

    M. A. d'Avila

    2005-03-01

    Full Text Available Nuclear magnetic resonance (NMR and magnetic resonance imaging (MRI have recently been recognized as important techniques for R&D of products and processes, as is attested by several successful applications in different areas of chemical engineering in recent years. In this article we present new experimental methods based on MRI to study flow and microstructure of concentrated emulsions. The objective is to present the unique features of this noninvasive technique to accurately measure different properties of flowing particulate opaque systems. Experimental results of velocity profiles, spatial distribution of droplet sizes and spatial homogeneity of an oil-in-water dispersion in a horizontal, concentric cylinder geometry using different pulse sequences are presented. The application of these techniques allowed probing important information on flow and microstructure of multiphase systems of interest in chemical engineering and food science.

  6. Adaptive optics scanning ophthalmoscopy with annular pupils.

    Science.gov (United States)

    Sulai, Yusufu N; Dubra, Alfredo

    2012-07-01

    Annular apodization of the illumination and/or imaging pupils of an adaptive optics scanning light ophthalmoscope (AOSLO) for improving transverse resolution was evaluated using three different normalized inner radii (0.26, 0.39 and 0.52). In vivo imaging of the human photoreceptor mosaic at 0.5 and 10° from fixation indicates that the use of an annular illumination pupil and a circular imaging pupil provides the most benefit of all configurations when using a one Airy disk diameter pinhole, in agreement with the paraxial confocal microscopy theory. Annular illumination pupils with 0.26 and 0.39 normalized inner radii performed best in terms of the narrowing of the autocorrelation central lobe (between 7 and 12%), and the increase in manual and automated photoreceptor counts (8 to 20% more cones and 11 to 29% more rods). It was observed that the use of annular pupils with large inner radii can result in multi-modal cone photoreceptor intensity profiles. The effect of the annular masks on the average photoreceptor intensity is consistent with the Stiles-Crawford effect (SCE). This indicates that combinations of images of the same photoreceptors with different apodization configurations and/or annular masks can be used to distinguish cones from rods, even when the former have complex multi-modal intensity profiles. In addition to narrowing the point spread function transversally, the use of annular apodizing masks also elongates it axially, a fact that can be used for extending the depth of focus of techniques such as adaptive optics optical coherence tomography (AOOCT). Finally, the positive results from this work suggest that annular pupil apodization could be used in refractive or catadioptric adaptive optics ophthalmoscopes to mitigate undesired back-reflections.

  7. Renal blood flow, early distal sodium, and plasma renin concentrations during osmotic diuresis

    DEFF Research Database (Denmark)

    Leyssac, P P; Holstein-Rathlou, N H; Skøtt, O

    2000-01-01

    .6 mmHg. Urine flow increased 10-fold, and sodium excretion increased by 177%. Plasma renin concentration (PRC) increased by 58%. Renal blood flow and glomerular filtration rate decreased, however end-proximal flow remained unchanged. After a similar volume of hypotonic glucose (152 mM), ED......(NaCl) increased by 3.6 mM, (P sodium excretion rate, or PRC. Infusion of 300 micromol NaCl in a smaller volume caused ED(NaCl) to increase by 6.4 mM without significant changes in PRC. Urine flow and sodium excretion increased significantly....... There was a significant inverse relationship between superficial nephron ED(NaCl) and PRC. We conclude that ED(Na) decreases during osmotic diuresis, suggesting that the increase in PRC was mediated by the macula densa. The results suggest that the natriuresis during osmotic diuresis is a result of impaired sodium...

  8. Estimation of Collection Efficiency Depended on Feed Particle Concentration for Axial Flow Cyclone Dust Collector

    Institute of Scientific and Technical Information of China (English)

    AkiraOgawa

    1999-01-01

    A cyclone dust collector is applied in many industries.Especially the axial flow cyclone is the most simple construction and if keeps high reliability for maintenance.On the other hand,the collection efficiency of the cyclone depends not only on the inlet gas velocity but also on the feed particle concentration.The collection efficiency increases with increasing feed particle concentration.However until now the problem of how to estimate the collection efficiency depended on the feed particle concentration is remained except the investigation by Muschelknautz & Brunner[6],Therefore in this paper one of the estimate method for the collection efficiency of the axial flow cyclones is proposed .The application to the geometrically similar type of cyclone of the body diameters D1=30,50,69and 99mm showed in good agreement with the experimental results of the collection efficiencies which were described in detail in the paper by ogawa & Sugiyama[8].

  9. New Method of Online Measurement of Oil and Suspended Material Concentration In Flowing Waste Water

    Science.gov (United States)

    Liao, Hongwei; Xu, Guobing; Xu, Xinqiang; Zhou, Fangde

    2007-06-01

    At present, the most of the measurements of oil and suspended material concentration in waste water measuring are not online surveys. A new method of online measurement of oil and suspended material concentration in flowing waste water is presented. The room experiments and field tests showed that it is suitable to waste water treatment on line. After sampling, It needed to measure immediately the concentration in first time. Then let sample to be in still in 10 - 20 seconds. After that the bulk concentration was measured in second time. Because of the suspended solids having heavy density, they would be dropped from waster water. During ultrasonic operation, emulsify the oil in waster water, the oil and suspended solid would be depart. After that the third time measurement was done. In thus way the concentrations of oil and suspended solids can be measured. At present there are two on-site equipments operating in the Changqing oilfield, and the results are pretty well.

  10. Analysis of Cold Flowfield of Multi—Annular Opposed Jets

    Institute of Scientific and Technical Information of China (English)

    H.F.Zhao; G.C.Benelli

    1992-01-01

    The technique of the use of multi-annular opposed jets as different from using swirl and bluff body creates an excellent recirculation zone with desired size in a large space.The size of ecirculation,the magnitude of reverse velocity and turbulence intensity are much greater than those formed by bluff body.Factors affecting the flowfield include the velocity ration of the opposed jets to the primary air J.the diameter and construction of the opposed jet ring,secondary air velocity and configuration,and confined or unconfined flow condition and so on.This method is a promising way for flame stabilization in combustion technology.

  11. Heat transfer and pressure drop in an annular channel with downflow

    Science.gov (United States)

    Dolan, F. X.; Crowley, C. J.; Qureshi, Z. H.

    The onset of a flow instability (OFI) determines the minimum flow rate for cooling in the flow channels of a nuclear fuel assembly. A test facility was constructed with full-scale models (length and diameter) of annular flow channels incorporating many instruments to measure heat transfer and pressure drop with downflow in the annulus. Tests were performed both with and without axial centering ribs at prototypical values of pressure, flow rate and uniform wall heat flux. The axial ribs have the effect of subdividing the annulus into quadrants, so the problem becomes one of parallel channel flow, unlike previous experiments in tubes (upflow and downflow). Other tests were performed to determine the effects if any of asymmetric and non-uniform circumferential wall heating, operating pressure level and dissolved gas concentration. Data from the tests are compared with models for channel heat transfer and pressure drop profiles in several regimes of wall heating from single-phase forced convection through partially and fully developed nucleate boiling. Minimum stable flow rates were experimentally determined as a function of wall heat flux and heat distribution and compared with the model for the transition to fully developed boiling which is a key criterion in determining the OFI condition in the channel. The heat transfer results in the channel without ribs are in excellent agreement with predictions from a computer model of the flow in the annulus and with empirical correlations developed from similar tests. The test results with centering ribs show that geometrical variations between the channels can lead to differences in subchannel behavior which can make the effect of the ribs and the geometry an important factor when assessing the power level at which the fuel assembly (and the reactor) can be operated to prevent overheating in the event of a loss-of-coolant-accident (LOCA).

  12. Measurement of Concentration Distribution of Hydrogen Gas Flow by Measuring the Intensity of Raman Scattering Light

    Science.gov (United States)

    Asahi, Ippei; Ninomiya, Hideki

    An experimental study to visualize and measure the concentration distribution of hydrogen gas flow using the Raman scattering was performed. A Nd:YAG laser of wavelength at 355 nm was used, and the beam pattern was transformed into a rectangle and a sheet beam was formed. The Raman scattered light was observed at a right angle with respect to the laser beam axis using a gated ICCD camera and an interference filter. Shadowgraph images were obtained at the same condition. The Raman scattering light image from atmospheric nitrogen was first acquired and the function of Raman scattering light acquisition and the background light suppression was confirmed. Next, images of the Raman scattering light image and shadowgraph of hydrogen gas discharged from a nozzle into the atmosphere were acquired. The two obtained Raman images were compared and the spatial concentration distribution of the flow of the hydrogen gas at different flow rates was calculated. This method is effective for visualizing the gas flow and measuring the concentration distribution of the Raman active molecules, such as hydrogen gas.

  13. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    Energy Technology Data Exchange (ETDEWEB)

    Prasetyaningrum, A., E-mail: ajiprasetyaningrum@gmail.com; Ratnawati,; Jos, B. [Department of Chemical Engineering, Faculty of Engineering, Diponegoro University Jl. Prof. H. Soedarto Tembalang, Semarang, Central Java, Indonesia, 50276 (Indonesia)

    2015-12-29

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  14. Sediment transport capacity of concentrated flows on steep loessial slope with erodible beds.

    Science.gov (United States)

    Xiao, Hai; Liu, Gang; Liu, Puling; Zheng, Fenli; Zhang, Jiaqiong; Hu, Feinan

    2017-05-24

    Previous research on sediment transport capacity has been inadequate and incomplete in describing the detachment and transport process of concentrated flows on slope farmlands during rill development. An indoor concentrated flow scouring experiment was carried out on steep loessial soil slope with erodible bed to investigate the sediment transport capacity under different flow rates and slope gradients. The results indicated that the sediment transport capacity increases with increasing flow rate and slope gradient, and these relationships can be described by power functions and exponential functions, respectively. Multivariate, nonlinear regression analysis showed that sediment transport capacity was more sensitive to slope gradient than to flow rate, and it was more sensitive to unit discharge per unit width than to slope gradient for sediment transport capacity in this study. When similar soil was used, the results were similar to those of previous research conducted under both erodible and non-erodible bed conditions. However, the equation derived from previous research under non-erodible bed conditions with for river bed sand tends to overestimate sediment transport capacity in our experiment.

  15. Periodic dislocation dynamics in two-dimensional concentrated emulsion flowing in a tapered microchannel

    Science.gov (United States)

    Gai, Ya; Leong, Chia Min; Cai, Wei; Tang, Sindy K. Y.

    2016-11-01

    Here we report a surprising order in concentrated emulsion when flowing as a monolayer in a tapered microfluidic channel. The flow of droplets in micro-channels can be non-trivial, and may lead to unexpected phenomena such as long-period oscillations and chaos. Previously, there have been studies on concentrated emulsions in straight channels and channels with bends. The dynamics of how drops flow and rearrange in a tapered geometry has not yet been characterized. At sufficiently slow flow rates, the drops arrange into a hexagonal lattice. At a given x-position, the time-averaged droplet velocities are uniform. The instantaneous drop velocities, however, reveal a different, wave-like pattern. Within the rearrangement zone where the number of rows of drops decreases from N to N-1, there is always a drop moved faster than the others. Close examination reveals the anomalous velocity profile arises from a series of dislocations that are both spatial and temporal periodic. To our knowledge, such reproducible dislocation motion has not been reported before. Our results are useful in novel flow control and mixing strategies in droplet microfluidics as well as modeling crystal plasticity in low-dimensional nanomaterials.

  16. Purification and concentration of influenza inactivated viruses by continuous-flow zonal centrifugation.

    Science.gov (United States)

    Mistretta, A P; Crovari-Cuneo, P; Giacometti, G; Sacchi, G; Strozzi, F

    1975-01-01

    A mathod is described for the purification, on an industrial scale, of influenza viruses grown in allantoic cavity of embryonated eggs. The mehtod consists of combining continuous-flow centrifugation with zonal centrifugation in a sucrose (36.6 per cent-52.5 per cent w/v) density gradient. The sample flow rate is approximately 3.7 litres/h and the volumes treated vary between 3 and 33 litres of allantoic fluid. Both the recovery of the virus and the degree of concentration and purification result satisfactory.

  17. Influence of Droplet Size on Exergy Destruction in Flow of Concentrated Non-Newtonian Emulsions

    Directory of Open Access Journals (Sweden)

    Rajinder Pal

    2016-04-01

    Full Text Available The influence of droplet size on exergy destruction rate in flow of highly concentrated oil-in-water emulsions was investigated experimentally in a cone and plate geometry. The oil concentration was fixed at 74.5% by volume. At this dispersed-phase (oil concentration, two different droplet size emulsions were prepared: fine and coarse emulsions. The fine and coarse emulsions were mixed in different proportions to vary the droplet size distribution. Although the dispersed and matrix phases of the emulsions were Newtonian in nature, the emulsions exhibited a non-Newtonian (shear-thinning behavior due to the high droplet concentration. The shear stress—shear rate data of the emulsions could be described adequately by a power law model. At low shear rates, the exergy destruction rate per unit volume of emulsion exhibited a minimum at a fine emulsion proportion of 35%. The results from the cone and plate geometry were used to simulate exergy loss in pipeline flow of emulsions. The pumping of emulsions becomes more efficient thermodynamically upon mixing of fine and coarse emulsions provided that the flow regime is maintained to be laminar and that the Reynolds number is kept at a low to moderate value. In the turbulent regime, the exergy loss generally increases upon mixing the fine and coarse emulsions.

  18. Harvesting Energy from Salinity Differences Using Battery Electrodes in a Concentration Flow Cell.

    Science.gov (United States)

    Kim, Taeyoung; Rahimi, Mohammad; Logan, Bruce E; Gorski, Christopher A

    2016-09-06

    Salinity-gradient energy (SGE) technologies produce carbon-neutral and renewable electricity from salinity differences between seawater and freshwater. Capacitive mixing (CapMix) is a promising class of SGE technologies that captures energy using capacitive or battery electrodes, but CapMix devices have produced relatively low power densities and often require expensive materials. Here, we combined existing CapMix approaches to develop a concentration flow cell that can overcome these limitations. In this system, two identical battery (i.e., faradaic) electrodes composed of copper hexacyanoferrate (CuHCF) were simultaneously exposed to either high (0.513 M) or low (0.017 M) concentration NaCl solutions in channels separated by a filtration membrane. The average power density produced was 411 ± 14 mW m(-2) (normalized to membrane area), which was twice as high as previously reported values for CapMix devices. Power production was continuous (i.e., it did not require a charging period and did not vary during each step of a cycle) and was stable for 20 cycles of switching the solutions in each channel. The concentration flow cell only used inexpensive materials and did not require ion-selective membranes or precious metals. The results demonstrate that the concentration flow cell is a promising approach for efficiently harvesting energy from salinity differences.

  19. Geometry optimization of linear and annular plasma synthetic jet actuators

    Science.gov (United States)

    Neretti, G.; Seri, P.; Taglioli, M.; Shaw, A.; Iza, F.; Borghi, C. A.

    2017-01-01

    The electrohydrodynamic (EHD) interaction induced in atmospheric air pressure by a surface dielectric barrier discharge (DBD) actuator has been experimentally investigated. Plasma synthetic jet actuators (PSJAs) are DBD actuators able to induce an air stream perpendicular to the actuator surface. These devices can be used in the field of aerodynamics to prevent or induce flow separation, modify the laminar to turbulent transition inside the boundary layer, and stabilize or mix air flows. They can also be used to enhance indirect plasma treatment effects, increasing the reactive species delivery rate onto surfaces and liquids. This can play a major role in plasma processing and chemical kinetics modelling, where often only diffusive mechanisms are considered. This paper reports on the importance that different electrode geometries can have on the performance of different PSJAs. A series of DBD aerodynamic actuators designed to produce perpendicular jets has been fabricated on two-layer printed circuit boards (PCBs). Both linear and annular geometries were considered, testing different upper electrode distances in the linear case and different diameters in the annular one. An AC voltage supplied at a peak of 11.5 kV and a frequency of 5 kHz was used. Lower electrodes were connected to the ground and buried in epoxy resin to avoid undesired plasma generation on the lower actuator surface. Voltage and current measurements were carried out to evaluate the active power delivered to the discharges. Schlieren imaging allowed the induced jets to be visualized and gave an estimate of their evolution and geometry. Pitot tube measurements were performed to obtain the velocity profiles of the PSJAs and to estimate the mechanical power delivered to the fluid. The optimal values of the inter-electrode distance and diameter were found in order to maximize jet velocity, mechanical power or efficiency. Annular geometries were found to achieve the best performance.

  20. Thermal and concentration stratifications effects in radiative flow of Jeffrey fluid over a stretching sheet.

    Science.gov (United States)

    Hayat, T; Hussain, Tariq; Shehzad, S A; Alsaedi, A

    2014-01-01

    In this article we investigate the heat and mass transfer analysis in mixed convective radiative flow of Jeffrey fluid over a moving surface. The effects of thermal and concentration stratifications are also taken into consideration. Rosseland's approximations are utilized for thermal radiation. The nonlinear boundary layer partial differential equations are converted into nonlinear ordinary differential equations via suitable dimensionless variables. The solutions of nonlinear ordinary differential equations are developed by homotopic procedure. Convergence of homotopic solutions is examined graphically and numerically. Graphical results of dimensionless velocity, temperature and concentration are presented and discussed in detail. Values of the skin-friction coefficient, the local Nusselt and the local Sherwood numbers are analyzed numerically. Temperature and concentration profiles are decreased when the values of thermal and concentration stratifications parameters increase. Larger values of radiation parameter lead to the higher temperature and thicker thermal boundary layer thickness.

  1. ON THE CONCENTRATION GRADIENT ACROSS A SPHERICAL SOURCE WASHED BY SLOW FLOW.

    Science.gov (United States)

    JAFFE, L

    1965-03-01

    A model has been numerically analyzed to help interpret the orienting effects of flow upon cells. The model is a sphere steadily and uniformly emitting a diffusible stuff into a medium otherwise free of it and moving past with Stokes flow. Its properties depend primarily upon the Peclet number, Pe, equal to a . v(infinity)/D, i.e., the sphere's radius, a, times the free stream speed, v(infinity), over the stuff's diffusion constant, D. As Pe rises, and washing becomes more effective, the average surface concentration, C(s a) falls (Figs. 2 and 5) and the residual material becomes relatively concentrated on the sphere's lee pole (Figs. 2 and 4). Specifically, as Pe rises from 0.1 to 1, the relative concentration gradient, G, rises from 0.7 to 5.0 per cent and to the point where it is rising at about 8 per cent per decade; by Pe 1000, G = 22.1 per cent. From Pe 1 through 1000, G/(1 - C(s a)), or the gradient per concentration deficiency remains at about 26 per cent suggesting that G approaches a ceiling of about 26 per cent. Also from Pe 1 through 1000, the average mass transfer co-efficient nearly equals that previously calculated for spheres maintaining constant surface concentration instead of flux. The complete differential equation without approximations, the Gauss-Seidel method, and an approximation for the outer boundary condition were used.

  2. [Estimation of average traffic emission factor based on synchronized incremental traffic flow and air pollutant concentration].

    Science.gov (United States)

    Li, Run-Kui; Zhao, Tong; Li, Zhi-Peng; Ding, Wen-Jun; Cui, Xiao-Yong; Xu, Qun; Song, Xian-Feng

    2014-04-01

    On-road vehicle emissions have become the main source of urban air pollution and attracted broad attentions. Vehicle emission factor is a basic parameter to reflect the status of vehicle emissions, but the measured emission factor is difficult to obtain, and the simulated emission factor is not localized in China. Based on the synchronized increments of traffic flow and concentration of air pollutants in the morning rush hour period, while meteorological condition and background air pollution concentration retain relatively stable, the relationship between the increase of traffic and the increase of air pollution concentration close to a road is established. Infinite line source Gaussian dispersion model was transformed for the inversion of average vehicle emission factors. A case study was conducted on a main road in Beijing. Traffic flow, meteorological data and carbon monoxide (CO) concentration were collected to estimate average vehicle emission factors of CO. The results were compared with simulated emission factors of COPERT4 model. Results showed that the average emission factors estimated by the proposed approach and COPERT4 in August were 2.0 g x km(-1) and 1.2 g x km(-1), respectively, and in December were 5.5 g x km(-1) and 5.2 g x km(-1), respectively. The emission factors from the proposed approach and COPERT4 showed close values and similar seasonal trends. The proposed method for average emission factor estimation eliminates the disturbance of background concentrations and potentially provides real-time access to vehicle fleet emission factors.

  3. Attenuation of concentration fluctuations of water vapor and other trace gases in turbulent tube flow

    DEFF Research Database (Denmark)

    Massman, W.J.; Ibrom, Andreas

    2008-01-01

    Recent studies with closed-path eddy covariance (EC) systems have indicated that the attenuation of fluctuations of water vapor concentration is dependent upon ambient relative humidity, presumably due to sorption/desorption of water molecules at the interior surface of the tube. Previous studies...... of EC-related tube attenuation effects have either not considered this issue at all or have only examined it superficially. Nonetheless, the attenuation of water vapor fluctuations is clearly much greater than might be expected from a passive tracer in turbulent tube flow. This study reexamines...... the turbulent tube flow issue for both passive and sorbing tracers with the intent of developing a physically-based semi-empirical model that describes the attenuation associated with water vapor fluctuations. Toward this end, we develop a new model of tube flow dynamics (radial profiles of the turbulent...

  4. Humic acid transport in saturated porous media:Influence of flow velocity and influent concentration

    Institute of Scientific and Technical Information of China (English)

    Xiaorong Wei; Mingan Shao; Lina Du; Robert Horton

    2014-01-01

    Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces.A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations.Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients,which resulted in an increased fraction of HA being retained in columns.Consequently,retardation factors were increased and the transport of HA through the columns was delayed.These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix.Accordingly,this attachment should be considered in studies of HA behavior in porous media.

  5. Modeling Particle Concentration In Slurry Flows Using Shear-Induced Migration: Theory vs. Experiments

    Science.gov (United States)

    Lin, Kanhui; Latterman, Paul; Koch, Trystan; Hu, Vincent; Ho, Joyce; Mata, Matthew; Murisic, Nebojsa; Bertozzi, Andrea

    2009-11-01

    Different flow regimes observed in our experimental study of particle-laden thin film flows are characterized by differing particle concentration profiles. We develop a theoretical model for particle concentration in order to capture our experimental observations. Our model is based on equilibrium assumption and it incorporates all relevant physical mechanisms, including shear-induced particle migration and settling due to gravity. It leads to a coupled system of ordinary differential equations for particle volume fraction and shear, which are solved numerically for various parameter sets. We find excellent agreement between our numerical results and experimental data. Our model is not only successful in reproducing the experimentally observed regimes, but also in capturing the connection between these regimes and the experimental parameters.

  6. Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

    Science.gov (United States)

    Wei, Xiaorong; Shao, Mingan; Du, Lina; Horton, Robert

    2014-12-01

    Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

  7. Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Sierra, Raymond G.; Gati, Cornelius; Laksmono, Hartawan; Dao, E. Han; Gul, Sheraz; Fuller, Franklin; Kern, Jan; Chatterjee, Ruchira; Ibrahim, Mohamed; Brewster, Aaron S.; Young, Iris D.; Michels-Clark, Tara; Aquila, Andrew; Liang, Mengning; Hunter, Mark S.; Koglin, Jason E.; Boutet, Sébastien; Junco, Elia A.; Hayes, Brandon; Bogan, Michael J.; Hampton, Christina Y.; Puglisi, Elisabetta V.; Sauter, Nicholas K.; Stan, Claudiu A.; Zouni, Athina; Yano, Junko; Yachandra, Vittal K.; Soltis, S. Michael; Puglisi, Joseph D.; DeMirci, Hasan

    2015-11-30

    We describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. We used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

  8. Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II.

    Science.gov (United States)

    Sierra, Raymond G; Gati, Cornelius; Laksmono, Hartawan; Dao, E Han; Gul, Sheraz; Fuller, Franklin; Kern, Jan; Chatterjee, Ruchira; Ibrahim, Mohamed; Brewster, Aaron S; Young, Iris D; Michels-Clark, Tara; Aquila, Andrew; Liang, Mengning; Hunter, Mark S; Koglin, Jason E; Boutet, Sébastien; Junco, Elia A; Hayes, Brandon; Bogan, Michael J; Hampton, Christina Y; Puglisi, Elisabetta V; Sauter, Nicholas K; Stan, Claudiu A; Zouni, Athina; Yano, Junko; Yachandra, Vittal K; Soltis, S Michael; Puglisi, Joseph D; DeMirci, Hasan

    2016-01-01

    We describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. We used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

  9. Flow patterns at the stenosed carotid bifurcation: effect of concentric versus eccentric stenosis.

    Science.gov (United States)

    Steinman, D A; Poepping, T L; Tambasco, M; Rankin, R N; Holdsworth, D W

    2000-04-01

    Carotid stenosis severity is a commonly used indicator for assessing risk of stroke. However, the majority of individuals with severe carotid artery disease never suffer a stroke, and strokes can occur even with only mild or moderate stenosis. This suggests local factors (other than stenosis severity) at or near the carotid artery bifurcation may be important in determining stroke risk. In this paper we investigate the effect of stenosis geometry on flow patterns in the stenosed carotid bifurcation, using concentrically and eccentrically stenosed anthropomorphic carotid bifurcation models having identical stenosis severity. Computational simulations and experimental flow visualizations both demonstrate marked differences in flow patterns of concentric and eccentric stenosis models for moderately and severely stenosed cases, respectively. In particular, we identify post-stenotic recirculation zone size and location, and spatial extent of elevated wall shear stress as key factors differing between the two geometries. As these are also rotid plaque more vulnerable to cerebral embolus prokey biophysical factors promoting thrombogenesis, we propose that the stenosed carotid bifurcation geometry--or the induced flow patterns themselves--may provide more specific indicators for those plaques that are vulnerable to enhanced thromboembolic potential, and hence, increased risk of ischemic stroke.

  10. Elliptic annular Josephson tunnel junctions in an external magnetic field: the statics

    DEFF Research Database (Denmark)

    Monaco, Roberto; Granata, Carmine; Vettoliere, Antonio

    2015-01-01

    symmetric electrodes a transverse magnetic field is equivalent to an in-plane field applied in the direction of the current flow. Varying the ellipse eccentricity we reproduce all known results for linear and ring-shaped JTJs. Experimental data on high-quality Nb/Al-AlOx/Nb elliptic annular junctions...... or in the perpendicular direction. We report a detailed study of both short and long elliptic annular junctions having different eccentricities. For junctions having a normalized perimeter less than one the threshold curves are derived and computed even in the case with one trapped Josephson vortex. For longer junctions...

  11. An improved experimental method for simulating erosion processes by concentrated channel flow.

    Science.gov (United States)

    Chen, Xiao-Yan; Zhao, Yu; Mo, Bin; Mi, Hong-Xing

    2014-01-01

    Rill erosion is an important process that occurs on hill slopes, including sloped farmland. Laboratory simulations have been vital to understanding rill erosion. Previous experiments obtained sediment yields using rills of various lengths to get the sedimentation process, which disrupted the continuity of the rill erosion process and was time-consuming. In this study, an improved experimental method was used to measure the rill erosion processes by concentrated channel flow. By using this method, a laboratory platform, 12 m long and 3 m wide, was used to construct rills of 0.1 m wide and 12 m long for experiments under five slope gradients (5, 10, 15, 20, and 25 degrees) and three flow rates (2, 4, and 8 L min(-1)). Sediment laden water was simultaneously sampled along the rill at locations 0.5 m, 1 m, 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 10 m, and 12 m from the water inlet to determine the sediment concentration distribution. The rill erosion process measured by the method used in this study and that by previous experimental methods are approximately the same. The experimental data indicated that sediment concentrations increase with slope gradient and flow rate, which highlights the hydraulic impact on rill erosion. Sediment concentration increased rapidly at the initial section of the rill, and the rate of increase in sediment concentration reduced with the rill length. Overall, both experimental methods are feasible and applicable. However, the method proposed in this study is more efficient and easier to operate. This improved method will be useful in related research.

  12. Modeling Flows and Concentrations of Nine Engineered Nanomaterials in the Danish Environment

    Directory of Open Access Journals (Sweden)

    Fadri Gottschalk

    2015-05-01

    Full Text Available Predictions of environmental concentrations of engineered nanomaterials (ENM are needed for their environmental risk assessment. Because analytical data on ENM-concentrations in the environment are not yet available, exposure modeling represents the only source of information on ENM exposure in the environment. This work provides material flow data and environmental concentrations of nine ENM in Denmark. It represents the first study that distinguishes between photostable TiO2 (as used in sunscreens and photocatalytic TiO2 (as used in self-cleaning surfaces. It also provides first exposure estimates for quantum dots, carbon black and CuCO3. Other ENM that are covered are ZnO, Ag, CNT and CeO2. The modeling is based for all ENM on probability distributions of production, use, environmental release and transfer between compartments, always considering the complete life-cycle of products containing the ENM. The magnitude of flows and concentrations of the various ENM depends on the one hand on the production volume but also on the type of products they are used in and the life-cycles of these products and their potential for release. The results reveal that in aquatic systems the highest concentrations are expected for carbon black and photostable TiO2, followed by CuCO3 (under the assumption that the use as wood preservative becomes important. In sludge-treated soil highest concentrations are expected for CeO2 and TiO2. Transformation during water treatments results in extremely low concentrations of ZnO and Ag in the environment. The results of this study provide valuable environmental exposure information for future risk assessments of these ENM.

  13. Measurement of Microsphere Concentration Using a Flow Cytometer with Volumetric Sample Delivery.

    Science.gov (United States)

    Wang, Lili; Zhang, Yu-Zhong; Choquette, Steven; Gaigalas, A K

    2014-01-01

    Microsphere concentrations are needed to assign equivalent reference fluorophores (ERF) units to microspheres used in quantitative flow cytometry. A flow cytometer with a syringe based sample delivery system was evaluated for the measurement of the concentration of microspheres contained in a vial of lyophilized microspheres certified by BD Biosciences to contain 50,600 microspheres. The concentration was measured by counting the number of microspheres contained in the volume delivered by the flow cytometer and dividing the number by the volume. The syringe volume was calibrated both in the delivery and draw modes, and the results of the volume calibration were summarized by two calibration lines. The delivered volume was obtained by dividing the number of recorded events by the concentration of microsphere count standard in the sample tube. The draw volume was obtained by weighting the sample tube before and after the draw. The slope of the draw volume calibration line was equal to 1.00 with an offset of -13 µL. The slope of the delivered volume calibration was 0.93 suggesting a systematic volume-dependent bias, which can be rationalized as an effect of suspension flow in capillaries. When the sample volume was set to values between 150 µL and 300 µL, both calibration curves gave similar results suggesting that a good estimate of the true delivered volume can be obtained by subtracting 13 µL from the delivered volume indicated by the syringe settings. The number of microspheres in the volume was obtained by passing the suspension contained in the volume through a laser beam and counting the number of events in which the signals from the scattering and fluorescence detectors exceeded threshold values. Measurements were performed with the lyophilized microspheres made by BD Biosciences and fluorescein microspheres (expired reference material RM 8640) in three buffers: a phosphate buffer saline (PBS), a buffer containing PBS and 0.05 % BSA (bovine serum albumin

  14. Temperature-dependent transformation thermotics for unsteady states: Switchable concentrator for transient heat flow

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ying, E-mail: 13110290008@fudan.edu.cn [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China); Shen, Xiangying, E-mail: 13110190068@fudan.edu.cn [Department of Physics, State Key Laboratory of Surface Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Huang, Jiping, E-mail: jphuang@fudan.edu.cn [Department of Physics, State Key Laboratory of Surface Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Ni, Yushan, E-mail: niyushan@fudan.edu.cn [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China)

    2016-04-22

    For manipulating heat flow efficiently, recently we established a theory of temperature-dependent transformation thermotics which holds for steady-state cases. Here, we develop the theory to unsteady-state cases by considering the generalized Fourier's law for transient thermal conduction. As a result, we are allowed to propose a new class of intelligent thermal metamaterial — switchable concentrator, which is made of inhomogeneous anisotropic materials. When environmental temperature is below or above a critical value, the concentrator is automatically switched on, namely, it helps to focus heat flux in a specific region. However, the focusing does not affect the distribution pattern of temperature outside the concentrator. We also perform finite-element simulations to confirm the switching effect according to the effective medium theory by assembling homogeneous isotropic materials, which bring more convenience for experimental fabrication than inhomogeneous anisotropic materials. This work may help to figure out new intelligent thermal devices, which provide more flexibility in controlling heat flow, and it may also be useful in other fields that are sensitive to temperature gradient, such as the Seebeck effect. - Highlights: • Established the unsteady-state temperature dependent transformation thermotics. • A thermal concentrator with switchable functionality. • An effective-medium design for experimental realization.

  15. A non-intrusive measurement technique applying CARS for concentration measurement in a gas mixing flow

    CERN Document Server

    Yamamoto, Ken; Moriya, Madoka; Kuriyama, Reiko; Sato, Yohei

    2015-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscope system was built and applied to a non-intrusive gas concentration measurement of a mixing flow in a millimeter-scale channel. Carbon dioxide and nitrogen were chosen as test fluids and CARS signals from the fluids were generated by adjusting the wavelengths of the Pump and the Stokes beams. The generated CARS signals, whose wavelengths are different from those of the Pump and the Stokes beams, were captured by an EM-CCD camera after filtering out the excitation beams. A calibration experiment was performed in order to confirm the applicability of the built-up CARS system by measuring the intensity of the CARS signal from known concentrations of the samples. After confirming that the measured CARS intensity was proportional to the second power of the concentrations as was theoretically predicted, the CARS intensities in the gas mixing flow channel were measured. Ten different measurement points were set and concentrations of both carbon dioxide and nitrog...

  16. Through an Annular Turbine Nozzle

    Directory of Open Access Journals (Sweden)

    Rainer Kurz

    1995-01-01

    is located in the gas turbine. The experiments were performed using total pressure probes and wall static pressure taps. The pitch variation modifies the flow field both upstream and downstream of the nozzle, although the experiments show that the effect is localized to the immediate neighborhood of the involved blades. The effects on the wakes and on the inviscid flow are discussed separately. The mean velocities show a strong sensitivity to the changes of the pitch, which is due to a potential flow effect rather than a viscous effect.

  17. Stitching algorithm for annular subaperture interferometry

    Institute of Scientific and Technical Information of China (English)

    Xi Hou; Fan Wu; Li Yang; Shibin Wu; Qiang Chen

    2006-01-01

    @@ Annular subaperture interferometry (ASI) has been developed for low cost and flexible test of rotationally symmetric aspheric surfaces, in which accurately combining the subaperture measurement data corrupted by misalignments and noise into a complete surface figure is the key problem. By introducing the Zernike annular polynomials which are orthogonal over annulus, a method that eliminates the coupling problem in the earlier algorithm based on Zernike circle polynomials is proposed. Vector-matrix notation is used to simplify the description and calculations. The performance of this reduction method is evaluated by numerical simulation. The results prove this method with high precision and good anti-noise capability.

  18. Annular, erythematous skin lesions in a neonate

    Directory of Open Access Journals (Sweden)

    Aparna Palit

    2012-01-01

    Full Text Available A 7-day-old premature female infant presented with rapidly progressive, erythematous, annular skin lesions from the 5 th day of life. She was diagnosed provisionally as a case of neonatal lupus erythematosus and was investigated accordingly. Histopathological examination of the skin biopsy specimen revealed presence of hyphae of dermatophytes in the stratum corneum, and the diagnosis was changed to tinea corporis. Differential diagnosis of the annular erythema of infancy has been discussed and the importance of scraping a scaly lesion for KOH preparation in the diagnostic work-up of such a patient has been highlighted.

  19. Optimal Thrust Vectoring for an Annular Aerospike Nozzle Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Recent success of an annular aerospike flight test by NASA Dryden has prompted keen interest in providing thrust vector capability to the annular aerospike nozzle...

  20. A compactly integrated flow cell with a chemiluminescent FIA system for determining lactate concentration in serum.

    Science.gov (United States)

    Nakamura, H; Murakami, Y; Yokoyama, K; Tamiya, E; Karube, I; Suda, M; Uchiyama, S

    2001-01-15

    We have fabricated an integrated flow cell as a total microanalysis system (microTAS). This flow cell (size, 15 x 20 mm; total inner volume, 12.2 microL) was designed for a rational analyzing system of lactate determination for serum. This cell was made by micromachining techniques and consisted of two hollows of a lactate oxidase (LOD) reactor and a mixing cell, a spiral groove, and three penetrated holes. To form the reactor and capillary, these patterns, etched on a silicon wafer, were attached to a glass plate by the anodic bonding method. A photodiode was put under part of the spiral capillary. The compactly accumulated devices were integrated into a flow injection analysis (FIA) system. In the flow cell, lactate was catalyzed to pyruvate and hydrogen peroxide at the LOD reactor; subsequently, hydrogen peroxide reacted with the luminol-ferricyanic reagent at the mixing cell. The resulting chemiluminescent light was detected by the photodiode. Using the miniaturized flow cell, the sample volume for one measurement was greatly reduced to 0.2 microL. The response to lactate was obtained within 30 s and was linear between 0.5 and 5.0 mM (4.5 and 45 mg/dL) lactate with excellent correlative variances of 3.2% (average of three measurements at 5.0 mM). For practical application, the lactate concentration in control human serum was determined using this system. The results showed a good correlation coefficient (r = 0.979) with the results obtained by the spectrophotometric reference method. No difference in sera (normal or pathological) was found. Consequently, this integrated flow cell shows potential as a clinical device for lactate determination in serum. In this article, the effect of the design on the chemiluminescent FIA system is also described.

  1. Entropy Generation in Flow of Highly Concentrated Non-Newtonian Emulsions in Smooth Tubes

    Directory of Open Access Journals (Sweden)

    Rajinder Pal

    2014-10-01

    Full Text Available Entropy generation in adiabatic flow of highly concentrated non-Newtonian emulsions in smooth tubes of five different diameters (7.15–26.54 mm was investigated experimentally. The emulsions were of oil-in-water type with dispersed-phase concentration (Φ ranging from 59.61–72.21% vol. The emulsions exhibited shear-thinning behavior in that the viscosity decreased with the increase in shear rate. The shear-stress (τ versus shear rate (˙γ data of emulsions could be described well by the power-law model: τ=K˙γn. The flow behavior index n was less than 1 and it decreased sharply with the increase in Φ whereas the consistency index K increased rapidly with the increase in Φ . For a given emulsion and tube diameter, the entropy generation rate per unit tube length increased linearly with the increase in the generalized Reynolds number ( Re_n on a log-log scale. For emulsions with Φ ≤65.15 % vol., the entropy generation rate decreased with the increase in tube diameter. A reverse trend in diameter-dependence was observed for the emulsion with Φ of 72.21% vol. New models are developed for the prediction of entropy generation rate in flow of power-law emulsions in smooth tubes. The experimental data shows good agreement with the proposed models.

  2. CFD Modeling of Flow, Temperature, and Concentration Fields in a Pilot-Scale Rotary Hearth Furnace

    Science.gov (United States)

    Liu, Ying; Su, Fu-Yong; Wen, Zhi; Li, Zhi; Yong, Hai-Quan; Feng, Xiao-Hong

    2014-01-01

    A three-dimensional mathematical model for simulation of flow, temperature, and concentration fields in a pilot-scale rotary hearth furnace (RHF) has been developed using a commercial computational fluid dynamics software, FLUENT. The layer of composite pellets under the hearth is assumed to be a porous media layer with CO source and energy sink calculated by an independent mathematical model. User-defined functions are developed and linked to FLUENT to process the reduction process of the layer of composite pellets. The standard k-ɛ turbulence model in combination with standard wall functions is used for modeling of gas flow. Turbulence-chemistry interaction is taken into account through the eddy-dissipation model. The discrete ordinates model is used for modeling of radiative heat transfer. A comparison is made between the predictions of the present model and the data from a test of the pilot-scale RHF, and a reasonable agreement is found. Finally, flow field, temperature, and CO concentration fields in the furnace are investigated by the model.

  3. Magnetohydrodynamic mixed convection flow in vertical concentric annuli with time periodic boundary condition: Steady periodic regime

    Indian Academy of Sciences (India)

    BASANT K JHA; BABATUNDE AINA

    2016-08-01

    This work reports an analytical solution for fully developed mixed convection flow of viscous,incompressible, electrically conducting fluid in vertical concentric annuli under the influence of a transverse magnetic field, where the outer surface of inner cylinder is heated sinusoidally and the inner surface of outercylinder is kept at a constant temperature. The analysis is carried out for fully developed parallel flow and steady-periodic regime. The governing dimensionless momentum and energy equations are separated into steadyand periodic parts and solved analytically. Closed form solutions are expressed in terms of modified Bessel function of first and second kind. The influence of each governing parameters such as magnetic field parameter,Prandtl number and the dimensionless frequency of heating on flow formation and thermal behaviour are discussed with the aid of graphs. During the course of investigation, it is found that the oscillation amplitude of the friction factor is maximized at a resonance frequency near the surface of the concentric annuli where there is periodic heating. Furthermore, increasing transverse magnetic field decreases the oscillation amplitude of the friction factor.

  4. Evaluation of a portable oxygen concentrator to provide fresh gas flow to dogs undergoing anesthesia.

    Science.gov (United States)

    Burn, Jessica; Caulkett, Nigel A; Gunn, Marta; Cooney, Claire; Kutz, Susan J; Boysen, Søren R

    2016-06-01

    This study evaluated the ability of a portable oxygen concentrator (POC) to provide fresh gas to an anesthetic machine via an Ayre's T-piece or a Bain circuit. Fraction of inspired oxygen (FiO2) was compared at flows of 0.5 to 3.0 L/min. Measured FiO2 was 96% at flow rates ≥ 1 L/min. Mean battery life at 1.0, 2.0, and 3.0 L/min was 4.21 ± 0.45, 2.62 ± 0.37 and 1.5 ± 0.07 hours, respectively. The POC proved to be useful and effective during 2 power outages. The POC was sufficient to prevent rebreathing in 70% of dogs using a T-piece circuit and 20% of dogs with a Bain circuit. A significant negative correlation between inspired CO2 and O2 flow rates was noted. A significant positive correlation between inspired CO2 and ETCO2 was documented. The occurrence of hypercarbia was associated with low O2 flow. Battery back-up was essential during power outages. The POC can be effectively used for delivery of anesthesia.

  5. Effect of flow velocity, substrate concentration and hydraulic cleaning on biofouling of reverse osmosis feed channels

    KAUST Repository

    Radu, Andrea I.

    2012-04-01

    A two-dimensional mathematical model coupling fluid dynamics, salt and substrate transport and biofilm development in time was used to investigate the effects of cross-flow velocity and substrate availability on biofouling in reverse osmosis (RO)/nanofiltration (NF) feed channels. Simulations performed in channels with or without spacer filaments describe how higher liquid velocities lead to less overall biomass amount in the channel by increasing the shear stress. In all studied cases at constant feed flow rate, biomass accumulation in the channel reached a steady state. Replicate simulation runs prove that the stochastic biomass attachment model does not affect the stationary biomass level achieved and has only a slight influence on the dynamics of biomass accumulation. Biofilm removal strategies based on velocity variations are evaluated. Numerical results indicate that sudden velocity increase could lead to biomass sloughing, followed however by biomass re-growth when returning to initial operating conditions. Simulations show particularities of substrate availability in membrane devices used for water treatment, e.g., the accumulation of rejected substrates at the membrane surface due to concentration polarization. Interestingly, with an increased biofilm thickness, the overall substrate consumption rate dominates over accumulation due to substrate concentration polarization, eventually leading to decreased substrate concentrations in the biofilm compared to bulk liquid. © 2012 Elsevier B.V.

  6. Application of flow-injection potentiometric system for determination of total concentration of aliphatic carboxylic acids.

    Science.gov (United States)

    Mroczkiewicz, Monika; Górski, Łukasz; Zamojska-Jaroszewicz, Anna; Szewczyk, Krzysztof W; Malinowska, Elżbieta

    2011-09-30

    In this work, flow-injection system with potentiometric detection was tested for determination of total carboxylic acid concentration. Detection part of the examined system consists of ion-selective electrodes (ISEs) with polymer membranes of different compositions. First electrode is based on Zr(IV)-tetraphenylporphyrin as ionophore selective towards carboxylic acid anions, the membrane of second one contains only liphophilic anion exchanger - tridodecylmethylammonium chloride. Final response of the system is a result of combination of EMF signals from both electrodes. Combination of two detectors enables significant decrease of differences between potentiometric signals induced by mixtures of studied anions of various concentrations as compared to results obtained only with metalloporphyrin-based ISE. The use of anion-exchanger based detector allows for elimination of the influence of aliphatic carboxylic acids lipophilicity. Proposed potentiometric flow-injection system was employed for determination of short-chain aliphatic carboxylic acids (so-called VFA - volatile fatty acids) in samples originating from an anaerobic digester. Results obtained for these relatively complicated samples are in good agreement with results obtained with the use of reference colorimetric method. Linear response towards carboxylic acids was observed in the concentration range of 10(-4) to 10(-2)mold m(-3), with the slopes in the range of -110 to -150 mV dec(-1) (for acetate(-) and butyrate(-), respectively). System enables for determination of about 6 samples per hour. Life time of ISEs average about 2 months.

  7. A Leaf-Inspired Luminescent Solar Concentrator for Energy-Efficient Continuous-Flow Photochemistry.

    Science.gov (United States)

    Cambié, Dario; Zhao, Fang; Hessel, Volker; Debije, Michael G; Noël, Timothy

    2017-01-19

    The use of solar light to promote chemical reactions holds significant potential with regard to sustainable energy solutions. While the number of visible light-induced transformations has increased significantly, the use of abundant solar light has been extremely limited. We report a leaf-inspired photomicroreactor that constitutes a merger between luminescent solar concentrators (LSCs) and flow photochemistry to enable green and efficient reactions powered by solar irradiation. This device based on fluorescent dye-doped polydimethylsiloxane collects sunlight, focuses the energy to a narrow wavelength region, and then transports that energy to embedded microchannels where the flowing reactants are converted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Contributions and Concerns of Concentrated Flow Erosion and Assessment Technologies in Watershed Systems

    Science.gov (United States)

    Bingner, R. L.; Momm, H. G.; Wells, R. R.; Dabney, S. M.

    2012-04-01

    Concentrated runoff increases erosion and efficiently transfers sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on cropland in the U.S. may contribute 40% of the sediment delivered to the edge of the field. Typically, conservation practices developed for sheet and rill erosion are also expected to treat ephemeral gully erosion, but technology and tools do not exist to account for the separate benefits and effects of practices on various sediment sources. Practices specifically developed to treat ephemeral gully erosion need further testing, when used in conjunction with sheet and rill erosion control practices. Without improved research studies, subjective observations will continue to be used to satisfy quality criteria in lieu of scientifically defensible, quantitative methods to estimate the impact of gully erosion. Some of the more important limiting components are the identification of and relationships for: (1) ephemeral gully width; (2) soil resistance to gully erosion including a definition for non-erosive layers; (3) the effect of root mass and above ground vegetation on erosion resistance; (4) ephemeral gully networks; and (5) the effect of subsurface flow on ephemeral gullies. Currently, these components are represented through widely divergent to non-existent algorithms. The U.S. Department of Agriculture's AnnAGNPS pollutant loading model has been developed to determine the effects of conservation management plans and provide sediment tracking from all sources within the watershed, including ephemeral gullies. Enhanced technology is also needed to identify where ephemeral gullies may form in the watershed using remote sensing technology. Developing enhanced technology and research for concentrated flow assessments is critical for developing and testing conservation practices specifically designed for gully erosion control. This study will describe the current state of concentrated flow assessment and

  9. [The concentration of viruses in water using the tangential flow ultrafiltration. Recovery effectiveness in experimental conditions].

    Science.gov (United States)

    Bigliardi, L; Cesari, C; Zoni, R; Sansebastiano, G E

    2004-01-01

    Poliovirus 1 concentration tests were carried out in artificially contaminated water by tangential flow ultrafiltration with Polisulfone filters 100000 MWCO. The tests were performed in 1 and in 20 liters of waters. The filters were conditioned and eluted respectively with Beef extract 3% and with glicina 1% at pH 7 and pH 9. The recovery mean using Beef extract resulted properly good, about the 83% and comparable to percentages we obtained in previous works with filters in cellulose nitrate and Virosorb filters. The viral recovery was low using the glicina for conditioning and eluting the filters.

  10. Non-Newtonian flow between concentric cylinders calculated from thermophysical properties obtained from simulations

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, A.P. [Univ. of Colorado, Boulder, CO (United States); Rainwater, J.C. [National Institute of Standards and Technology, Boulder, CO (United States); Hanley, H.J.M. [Univ. of Colorado, Boulder, CO (United States)]|[National Institute of Standards and Technology, Boulder, CO (United States)

    1995-03-01

    A study of the Weissenberg effect (rod climbing in a stirred system) based on nonequilibrium molecular dynamics (NEMD) is reported. Simulation results from a soft-sphere fluid are used to obtain a self-consistent free-surface profile of the fluid of finite compressibility undergoing Couette flow between concentric cylinders. A numerical procedure is then applied to calculate the height profile for a hypothetical fluid with thermophysical properties of the soft-sphere liquid and of a dense colloidal suspension. The height profile calculated is identified with shear thickening and the forms of the viscometric functions. The maximum climb occurs between the cylinders rather than at the inner cylinder.

  11. Annular beam with segmented phase gradients

    Directory of Open Access Journals (Sweden)

    Shubo Cheng

    2016-08-01

    Full Text Available An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

  12. Fluxon Dynamics in Elliptic Annular Josephson Junctions

    DEFF Research Database (Denmark)

    Monaco, Roberto; Mygind, Jesper

    2016-01-01

    We analyze the dynamics of a magnetic flux quantum (current vortex) trapped in a current-biased long planar elliptic annular Josephson tunnel junction. The system is modeled by a perturbed sine-Gordon equation that determines the spatial and temporal behavior of the phase difference across the tu...

  13. Annular beam with segmented phase gradients

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Shubo; Wu, Liang [School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China); Tao, Shaohua, E-mail: eshtao@csu.edu.cn [School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China); Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083 (China)

    2016-08-15

    An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

  14. Annular lichenoid syphilis: A rare entity.

    Science.gov (United States)

    Khurana, Ananta; Singal, Archana; Gupta, Seema

    2014-01-01

    Syphilis is a disease known for centuries, but still continues to be a diagnostic challenge as the myriad manifestations of secondary syphilis can mimic a lot many dermatological disorders. Lichenoid syphilis is an uncommon entity, reported only occasionally in the penicillin era. We present the case of a 32-year-old woman presenting with localized annular lichenoid lesions on the neck.

  15. A New Annular Shear Piezoelectric Accelerometer

    DEFF Research Database (Denmark)

    Liu, Bin; Kriegbaum, B.

    2000-01-01

    This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...... interface for sensors including mixed-mode communication protocols and transducer electronic data sheet (TEDS)....

  16. Flow synthesis using gaseous ammonia in a Teflon AF-2400 tube-in-tube reactor: Paal-Knorr pyrrole formation and gas concentration measurement by inline flow titration.

    Science.gov (United States)

    Cranwell, Philippa B; O'Brien, Matthew; Browne, Duncan L; Koos, Peter; Polyzos, Anastasios; Peña-López, Miguel; Ley, Steven V

    2012-08-14

    Using a simple and accessible Teflon AF-2400 based tube-in-tube reactor, a series of pyrroles were synthesised in flow using the Paal-Knorr reaction of 1,4-diketones with gaseous ammonia. An inline flow titration technique allowed measurement of the ammonia concentration and its relationship to residence time and temperature.

  17. Temperature and Concentration Traces of Spray Flows During Motion in a Flame

    Directory of Open Access Journals (Sweden)

    Antonov Dmitry V.

    2016-01-01

    Full Text Available Heat and mass transfer models are developed on the base of experimental data and using Ansys Fluent software. These models allow prediction of the temperature and concentration traces of droplets. Transfer mechanisms of water droplets from different flames of flammable liquid (ethanol, kerosene И benzine with temperature gases 450–850 К are analyzed. The paper considers aerosol flows with droplets sizes of 0.04–0.4 mm and concentration of 3.8·10-5 –10.3·10-5 m3 of droplets/m3 of gas. The maximum gas temperature reduction in the trace of a moving liquid is ranged from 850 K to 600 K. The times of keeping the low temperature of the gas-vapor mixture in the droplets trace are from 13 s to 25 s relative to the initial gas temperature.

  18. Probability density function modeling of scalar mixing from concentrated sources in turbulent channel flow

    CERN Document Server

    Bakosi, J; Boybeyi, Z; 10.1063/1.2803348

    2010-01-01

    Dispersion of a passive scalar from concentrated sources in fully developed turbulent channel flow is studied with the probability density function (PDF) method. The joint PDF of velocity, turbulent frequency and scalar concentration is represented by a large number of Lagrangian particles. A stochastic near-wall PDF model combines the generalized Langevin model of Haworth & Pope with Durbin's method of elliptic relaxation to provide a mathematically exact treatment of convective and viscous transport with a non-local representation of the near-wall Reynolds stress anisotropy. The presence of walls is incorporated through the imposition of no-slip and impermeability conditions on particles without the use of damping or wall-functions. Information on the turbulent timescale is supplied by the gamma-distribution model of van Slooten et al. Two different micromixing models are compared that incorporate the effect of small scale mixing on the transported scalar: the widely used interaction by exchange with th...

  19. Design Attributes and Scale Up Testing of Annular Centrifugal Contactors

    Energy Technology Data Exchange (ETDEWEB)

    David H. Meikrantz; Jack D. Law

    2005-04-01

    Annular centrifugal contactors are being used for rapid yet efficient liquid- liquid processing in numerous industrial and government applications. Commercialization of this technology began eleven years ago and now units with throughputs ranging from 0.25 to 700 liters per minute are readily available. Separation, washing, and extraction processes all benefit from the use of this relatively new commercial tool. Processing advantages of this technology include: low in-process volume per stage, rapid mixing and separation in a single unit, connection-in-series for multi-stage use, and a wide operating range of input flow rates and phase ratios without adjustment. Recent design enhancements have been added to simplify maintenance, improve inspection ability, and provide increased reliability. Cartridge-style bearing and mechanical rotary seal assemblies that can include liquid-leak sensors are employed to enhance remote operations, minimize maintenance downtime, prevent equipment damage, and extend service life. Clean-in-place capability eliminates the need for disassembly, facilitates the use of contactors for feed clarification, and can be automated for continuous operation. In nuclear fuel cycle studies, aqueous based separations are being developed that efficiently partition uranium, actinides, and fission products via liquid-liquid solvent extraction. Thus, annular centrifugal contactors are destined to play a significant role in the design of such new processes. Laboratory scale studies using mini-contactors have demonstrated feasibility for many such separation processes but validation at an engineering scale is needed to support actual process design.

  20. DNBR Analysis of a Dual-Cooled Annular Fuel for the OPR1000 Application

    Energy Technology Data Exchange (ETDEWEB)

    Shin, C. H.; In, W. K.; Oh, D. S.; Chun, T. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    A dual-cooled annular fuel for a pressurized water reactor (PWR) has been introduced for a significant amount of reactor power uprate. The Korea Atomic Energy Research Institute (KAERI) has been performing a research to develop a dual-cooled annular fuel for the power uprate of 20% in an optimized PWR in Korea, OPR1000. Several thermal-hydraulic tasks exist for the application of the dual-cooled annular fuel to OPR1000. The primary task is the balance of the minimum DNBR (MDNBR) between the inner and outer channels since the coolant flows through the circular inner channel of annular fuel as well as the outer subchannels formed between the fuel rods. The MDNBR balance has been known to largely depend on the thermal conductance in the inner and outer gaps. Another task is to evaluate the operating condition that the inner coolant channel is partially blocked. This study calculated the MDNBR in the inner and outer channels depending on the thermal gap conductance, i.e., inner and outer gap width. The acceptable range of gap width is determined for the MDNBR not to exceed the DNBR limit during anticipated operational occurrences (AOOs) as well as normal operation. The limit for the flow blockage in the inner channel is also estimated based on the DNBR analysis

  1. Photosensitizer fluorescence dynamics at its diffusion in blood flow for different means of cells concentrations

    Science.gov (United States)

    Maryakhina, V. S.; Gun'kov, V. V.

    2016-04-01

    In the paper the mathematical model of kinetics of interaction of the injected compound with biological liquid flow has been described for different means of cells concentrations connected on packed cell volume. It is considered that biological liquid contains a three phases such as water, peptides and cells. At the time, the injected compound can interact with peptides and cells which are "trap" for him. The obtained distribution of the compound connects on changes of its fluorescence spectra. It is shown that fluorescence intensivity change is different at 560, 580 and 590 nm. The curves do not have monotonic nature. There is a sharp curves decline in the first few seconds, next, it are increasing. Curves inflection time slightly depends on the cells concentration and is 7-9 seconds. At the time stationary concentration significantly depends on this parameter in contrast to blood viscosity. As long s cells concentration is primarily mean of the packed cell volume, the model can be important for pharmacokinetics and preparations delivery. It can be also used for fluorescent biomedical diagnostics of cancer tumour.

  2. 幂律非牛顿流体在偏心圆环管中流动和传热的数值计算%Numerical calculation of flow and heat transfer for non-Newtonian fluid in eccentric annular channel

    Institute of Scientific and Technical Information of China (English)

    张钧波; 张敏

    2014-01-01

    This paper studies power-law non-Newtonian fluid where the shearing stress accords with the Ostwald-de Waele relational formula.It aims to solve the problem of the apparent viscosity changing with the shearing rates and the calculation which is different from Newtonian fluid.Cell-based central method is used for the non-linear viscosity coefficient discretization.It adopts FVM for flow and heat transfer numerical simulation of fully developed laminar in eccentric annular channel.The calculation results show that the power-law factor has a great impact on the fluid flow,but the impact on the heat transfer is influenced by the eccentricity .The eccentric-ity of annular channel can lead to the asymmetrical distribution of circumferential temperature and velocity.%以剪切应力符合Ostwald-de Waele关系式的幂律非牛顿流体为研究对象。针对幂律非牛顿流体的表观黏度随剪切速率变化且计算过程有别于牛顿流体的问题,运用基元中心法对非线性粘性系数进行离散。采用有限体积法对幂律非牛顿流体在偏心圆环管中的充分发展层流流动和传热进行数值计算。计算结果表明流体的幂律因子对流动的影响较大,但对传热的影响受到到偏心率的影响。流道偏心会引起圆环通道内速度和温度的周向分布不均匀,且偏心程度越严重,周向分布不均匀性越强烈。

  3. The Effects of Heterogeneity in Magma Water Concentration on the Development of Flow Banding and Spherulites in Rhyolitic Lava

    Energy Technology Data Exchange (ETDEWEB)

    Seaman, S.; Dyar, D; Marinkovic, N

    2009-01-01

    This study focuses on the origin of flow-banded rhyolites that consist of compositionally similar darker and lighter flow bands of contrasting texture and color. Infrared radiation was used to obtain Fourier transform infrared (FTIR) spectra from which water concentrations were calculated, and to map variations in water concentrations across zones of spherulites and glass from the 23 million year old Sycamore Canyon lava flow of southern Arizona. Lighter-colored, thicker flow bands consist of gray glass, fine-grained quartz, and large (1.0 to 1.5 mm) spherulites. Darker-colored, thinner flow bands consist of orange glass and smaller (0.1 to 0.2 mm) spherulites. The centers of both large and small spherulites are occupied by either (1) a quartz or sanidine crystal, (2) a granophyric intergrowth, or (3) a vesicle. Mapping of water concentration (dominantly OH- in glass and OH- and H2O in sanidine crystals) illustrates fluctuating water availability during quenching of the host melt. Textures of large spherulites in the lighter (gray) bands in some cases indicate complex quenching histories that suggest that local water concentration controlled the generation of glass versus crystals. Small spherulites in darker (orange) bands have only one generation of radiating crystal growth. Both the glass surrounding spherulites, and the crystals in the spherulites contain more water in the gray flow bands than in the orange flow bands. Flow banding in the Sycamore Canyon lava flow may have originated by the stretching of a magma that contained pre-existing zones (vesicles or proto-vesicles) of contrasting water concentration, as the magma flowed in the conduit and on the surface. Variation in the original water concentration in the alternating layers is interpreted to have resulted in differences in undercooling textures in spherulites in the lighter compared to the darker flow bands.

  4. A joint velocity-concentration PDF method for tracer flow in heterogeneous porous media

    Science.gov (United States)

    Meyer, Daniel W.; Jenny, Patrick; Tchelepi, Hamdi A.

    2010-12-01

    The probability density function (PDF) of the local concentration of a contaminant, or tracer, is an important component of risk assessment in applications that involve flow in heterogeneous subsurface formations. In this paper, a novel joint velocity-concentration PDF method for tracer flow in highly heterogeneous porous media is introduced. The PDF formalism accounts for advective transport, pore-scale dispersion (PSD), and molecular diffusion. Low-order approximations (LOAs), which are usually obtained using a perturbation expansion, typically lead to Gaussian one-point velocity PDFs. Moreover, LOAs provide reasonable approximations for small log conductivity variances (i.e., σY2 Caroni and Fiorotto (2005) for saturated transport in velocity fields, which are stationary in space and time, for domains with σY2 = 0.05, 1, and 2 and Péclet numbers ranging from 100 to 10,000. PSD is modeled using constant anisotropic dispersion coefficients in both the reference MC computations and our PDF method.

  5. Energy efficiency of a concentration gradient flow battery at elevated temperatures

    Science.gov (United States)

    van Egmond, W. J.; Starke, U. K.; Saakes, M.; Buisman, C. J. N.; Hamelers, H. V. M.

    2017-02-01

    Fast growth of intermittent renewable energy generation introduces a need for large scale electricity storage. The Concentration Gradient Flow Battery (CGFB) is an emerging technology which combines Electrodialysis with Reverse Electrodialysis into a flow battery which is able to safely store very large amounts of energy in environmental friendly NaCl solutions. In this work, (dis)charge efficiency, energy density and power density are both theoretically and experimentally investigated. Fifteen constant current experiments (-47.5 to +37.5 A m-2) are performed at 40 °C and two experiments (-32.5 and 15 A m-2) at 10 and 25 °C. The magnitudes of the three main energy dissipation sources (internal resistance, water transport and co-ion transport) are measured and mitigation strategies are proposed. The effect of current density, state of charge and temperature on the dissipation sources is analysed. Water transport is shown to cause hysteresis, lower (dis)charge efficiencies and lower energy capacity. At constant current and with increasing temperature, internal resistance is reduced but unwanted water transport is increased. This study reports charge efficiencies up to 58% and discharge efficiencies up to 72%. Full charge or discharge of the battery is shown inefficient. The optimal operating range is therefore introduced and identified (concentration difference Δm > 0.5 and energy efficiency η > 0.4).

  6. Multifold Laser Resonator for Annular Gain Media.

    Science.gov (United States)

    Duncan, Arlene

    Available from UMI in association with The British Library. A pair of spherical mirrors enclosing an off-axis beam in a hyperboloidal ray trajectory describes a Herriott Cell. Placed inside a linear Fabry Perot resonator, a multifold laser resonator is formed. By considering this resonator when coupled to a coaxial, annular geometry, RF discharge excited CO_2 gain media in a sealed-off configuration, this thesis aims to formulate the scaling laws and characterise the main features of these devices. To help establish a design baseline and to allow the determination of practical results, the scaling laws are developed with an (arbitrary) limit on the physical size of the laser module of 100 x 10 x 10cm. Within this size, design algorithms demonstrate the limitation on scaling power to about 460W. Output beam characteristics are investigated for a range of multifold lasers to determine the effects the choice of design parameters has and the predicted TEM _{00} output expected. All incongruities are found to be primarily dependent on whether or not the beam traverses the complete Herriott Cell, but more directly on the radial gain and refractive index variations present in the gain medium. In terms of polarization, image rotation and astigmatism, the Cell has been analysed to determine the non-planar influence. Theoretical and experimental results tie in with the conclusions from the previous observations. The use of tolerance equations and a study of deviations in beam spot positions on the mirrors under misalignments illustrates; dependence on electrode dimensions; greatest sensitivity to Cell mirror tilts; and a shift in the ray envelope cross-section from circular to elliptical on all resonator adjustments. At all stages results are compared with existing multifold lasers and other lasers with similar output powers. As a whole the thesis demonstrates the potential of these lasers in the medium power range as sealed-off devices with excellent mode quality. Increased

  7. Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

    Directory of Open Access Journals (Sweden)

    Krupička Jan

    2014-06-01

    Full Text Available Principles of gamma-ray-based measurement are summarized and their application is demonstrated on an operation of the radiometric facility installed in the test loop for slurry flows at the Institute of Hydrodynamics. The facility is able to measure vertical profiles of chord-averaged concentrations and concentration maps in the pipe cross section. A methodology of measurement is proposed including detection and quantification of random and systematic errors. Experimental results are discussed in the light of the proposed methodology. Experimentally determined vertical profiles of concentration are presented for slurry flows of four different fractions of glass beads. The tomographic application of the radiometric device is demonstrated on a measured concentration map and a suitable image reconstruction method is tested. High reliability of measured concentration distributions is proved except for regions near the pipe wall. The radiometric method is shown to be a useful tool for measurement of concentration distribution in slurry flow through a pipe.

  8. Water demand for ecosystem protection in rivers with hyper-concentrated sediment-laden flow

    Institute of Scientific and Technical Information of China (English)

    LUO Huaming; LI Tianhong; NI Jinren; WANG Yudong

    2004-01-01

    Sediment transport is one of the main concerns in a river system with hyper-concentrated flows. Therefore, the water use for sediment transport must be considered in study on the water demand for river ecosystem. The conventional methods for calculating the Minimum Water Demand for River Ecosystem (MWDRE) are not appropriate for rivers with high sediment concentration. This paper studied the MWDRE in wet season, dry season and the whole year under different water-and-sediment conditions in the Lower Yellow River, which is regarded as a typical river with sediment-laden flows. The characteristics of MWDRE in the river are analyzed. Firstly,the water demand for sediment transport (WDST) is much larger than the demands for other riverine functions, the WDST accounts for the absolute majority of the MWDRE.Secondly, in wet season when the WDST is satisfied, not only most of the annual incoming sediment can be transported downstream, but also the water demands for other river functions can be satisfied automatically, so that the MWDRE in wet season is identical to the WDST. Thirdly, in dry season, when the WDST is satisfied, the water demands for other river functions can also be satisfied, but the low sediment transport efficiency results in significant waste of water resources. According to these characteristics and aiming at decreasing sediment deposition in the riverbed and improving the utilization efficiency of water resources, hydrological engineering works can be used to regulate or control flow and sediment so that the sediment incoming in dry season can be accumulated and be transported downstream intensively and thus efficiently in wet season.

  9. Miniaturized, High Flow, Low Dead Volume Pre-Concentrator for Trace Contaminants in Water under Microgravity Conditions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. proposes to develop a miniaturized high flow, low dead-volume pre-concentrator for monitoring trace levels of contaminants in water under...

  10. Modeling of the Flow, Temperature and Concentration Fields in an Arc Plasma Reactor with Argon-Nitrogen Atmosphere

    National Research Council Canada - National Science Library

    Fudolig, Agustin M; Nogami, Hiroshi; Yagi, Jun-ichiro

    1996-01-01

    A mathematical formulation was developed for describing the flow behavior, temperature profile and concentration fields in pure or mixed argon and nitrogen arc plasmas impinging on a metal target inside a reactor...

  11. Electroactive liquid lens driven by an annular membrane.

    Science.gov (United States)

    Wei, Kang; Domicone, Nicholas Wade; Zhao, Yi

    2014-03-01

    Unlike traditional focalization that recruits multiple moving lens elements to adjust focus, liquid lenses deliver adaptive focusing by simply tuning the surface profile of liquid or the elastomer that encloses liquid. Its simple and compact configuration, low cost, and actuation efficiency promise wide industrial, medical, and consumer applications. Dielectric elastomers (DEs), one type of commercially available soft active material, have been a good fit for creating adaptive optics. In this Letter, we present an adaptive, membrane-sealed liquid lens hydrostatically coupled to a concentric annular DE actuator. Electric actuation deforms the annular DE, which induces fluid transmission between the lens part and the actuation part for lens actuation. The maximum measured focal range was from 25.4 to 105.2 mm within 1.0 kV, which significantly outperforms the existing DE-actuated liquid lenses and eliminates the need for prestraining. The lens also enables varied focal ranges by simply adjusting its initial surface sagitta, providing flexibility for practical imaging applications.

  12. Effect of swirling flow on platelet concentration distribution in small-caliber artificial grafts and end-to-end anastomoses

    Institute of Scientific and Technical Information of China (English)

    Fan Zhan; Yu-Bo Fan; Xiao-Yan Deng

    2011-01-01

    Platelet concentration near the blood vessel wall is one of the major factors in the adhesion of platelets to the wall.In our previous studies,it was found that swirling flows could suppress platelet adhesion in small-caliber artificial grafts and end-to-end anastomoses.In order to better understand the beneficial effect of the swirling flow,we numerically analyzed the near-wall concentration distribution of platelets in a straight tube and a sudden tubular expansion tube under both swirling flow and normal flow conditions.The numerical models were created based on our previous experimental studies.The simulation results revealed that when compared with the normal flow,the swirling flow could significantly reduce the near-wall concentration of platelets in both the straight tube and the expansion tube.The present numerical study therefore indicates that the reduction in platelet adhesion under swirling flow conditions in small-caliber arterial grafts,or in end-to-end anastomoses as observed in our previous experimental study,was possibly through a mechanism of platelet transport,in which the swirling flow reduced the near-wall concentration of platelets.

  13. Application of Cross-Flow Filtration Technique in Purification and Concentration of Juice from Vietnamese Fruits

    Directory of Open Access Journals (Sweden)

    Huynh Cang Mai

    2017-09-01

    Full Text Available This study is to offer a 1st insight in the use of membrane process for the purification and concentration of Vietnamese fruit juices: cashew apple (Anacardium occidentale Line., dragon fruit (Cactus hémiépiphytes, pineapple (Ananas comosus, pomelo (Citrus grandis L., and gac aril oil (Momordica cochinchinensis Spreng.. On a laboratory scale, the effect of different operating parameters such as trans-membrane pressures (TMP, temperature and membrane pore sizes on permeate flux was determined in order to optimize process conditions that would ensure acceptable flux with adequate juice quality. The quality of the samples coming from the ultrafiltration (UF process was evaluated in terms of: total soluble solids (TSS, suspended solids (SS, and vitamin C. For example, the purification process of cashew apple juice by cross-flow filtration was optimized at 0.5 μm membrane pore size, 2.5 bars TMP, and 60 min filtration time. Besides, this technique was applied to enhance carotenoids concentration from gac oil. Optimum conditions for a high permeate flux and a good carotenoids retention are 5 nm, 2 bars, and 40 °C of membrane pore size, TMP, and temperature, respectively. Carotenoids were concentrated higher than that in feeding oil.

  14. Predicting the Mean Liquid Film Thickness and Profile along the Annular Length of a Uniformly Heated Channel at Dryout

    Directory of Open Access Journals (Sweden)

    V.Y. Agbodemegbe

    2011-03-01

    Full Text Available The objective of this study was to predict the mean liquid film thickness and profile at high shear stress using a mechanistic approach. Knowledge of the liquid film thickness and its variation with two-phase flow parameters is critical for the estimation of safety parameters in the annular flow regime. The mean liquid film thickness and profile were predicted by the PLIFT code designed in Fortran 95 programming language using the PLATO FTN95 compiler. The film thickness was predicted within the annular flow regime for a flow boiling quality ranging from 40 to 80 % at high interfacial shear stress. Results obtained for a laminar liquid film flow were dumped into an excel file when the ratio of the actual predicted film thickness to the critical liquid film thickness lied within the range of 0.9 to unity. The film thickness was observed to decrease towards the exit of the annular regime at high flow boiling qualities and void fractions. The observation confirmed the effect of evaporation in decreasing the film thickness as quality is increased towards the exit of the annular regime.

  15. Mathematical Modeling of the Concentrated Energy Flow Effect on Metallic Materials

    Directory of Open Access Journals (Sweden)

    Sergey Konovalov

    2016-12-01

    Full Text Available Numerous processes take place in materials under the action of concentrated energy flows. The most important ones include heating together with the temperature misdistribution throughout the depth, probable vaporization on the surface layer, melting to a definite depth, and hydrodynamic flotation; generation of thermo-elastic waves; dissolution of heterogeneous matrix particles; and formation of nanolayers. The heat-based model is presented in an enthalpy statement involving changes in the boundary conditions, which makes it possible to consider melting and vaporization on the material surface. As a result, a linear dependence of penetration depth vs. energy density has been derived. The model of thermo-elastic wave generation is based on the system of equations on the uncoupled one-dimensional problem of dynamic thermo-elasticity for a layer with the finite thickness. This problem was solved analytically by the symbolic method. It has been revealed for the first time that the generated stress pulse comprises tension and compression zones, which are caused by increases and decreases in temperature on the boundary. The dissolution of alloying elements is modeled on the example of a titanium-carbon system in the process of electron beam action. The mathematical model is proposed to describe it, and a procedure is suggested to solve the problem of carbon distribution in titanium carbide and liquid titanium-carbide solution in terms of the state diagram and temperature changes caused by phase transitions. Carbon concentration vs. spatial values were calculated for various points of time at diverse initial temperatures of the cell. The dependence of carbon particle dissolution on initial temperature and radius of the particle were derived. A hydrodynamic model based on the evolution of Kelvin-Helmholtz instability in shear viscous flows has been proposed to specify the formation of nanostructures in materials subjected to the action of concentrated

  16. Fast High Capacity Annular Gas Puff Valve Design Concept

    Science.gov (United States)

    Ruden, Edward

    2000-10-01

    A fast opening gas valve design concept is presented that can theoretically inject a few grams of D2 gas radially outward into a coaxial annular vacuum region with a radius of about 10 cm in less that 100 μ s. The concept employs a single turn 20-30 T pulsed magnetic field coil that axially accelerates an Mg alloy ring, which seals a gas plenum, to high velocity, releasing the gas. Both coil and ring are profiled to minimize stress in the ring. Such a device could be used to supply the initial gas load for a proposed 5 MJ Dense Plasma Focus driven by AFRL's Shiva Star Capacitor bank. The intent here is keep the vacuum current feed insulator under high vacuum during the discharge to avoid surface breakdown. Alternatively, a high energy rep ratable plasma flow opening switch could be supplied with such a valve. This work is funded by the USAF.

  17. Bacterial screening of platelet concentrates on day 2 and 3 with flow cytometry: the optimal sampling time point?

    Science.gov (United States)

    Vollmer, Tanja; Schottstedt, Volkmar; Bux, Juergen; Walther-Wenke, Gabriele; Knabbe, Cornelius; Dreier, Jens

    2014-07-01

    There is growing concern on the residual risk of bacterial contamination of platelet concentrates in Germany, despite the reduction of the shelf-life of these concentrates and the introduction of bacterial screening. In this study, the applicability of the BactiFlow flow cytometric assay for bacterial screening of platelet concentrates on day 2 or 3 of their shelf-life was assessed in two German blood services. The results were used to evaluate currently implemented or newly discussed screening strategies. Two thousand and ten apheresis platelet concentrates were tested on day 2 or day 3 after donation using BactiFlow flow cytometry. Reactive samples were confirmed by the BacT/Alert culture system. Twenty-four of the 2,100 platelet concentrates tested were reactive in the first test by BactiFlow. Of these 24 platelet concentrates, 12 were false-positive and the other 12 were initially reactive. None of the microbiological cultures of the initially reactive samples was positive. Parallel examination of 1,026 platelet concentrates by culture revealed three positive platelet concentrates with bacteria detected only in the anaerobic culture bottle and identified as Staphylococcus species. Two platelet concentrates were confirmed positive for Staphylcoccus epidermidis by culture. Retrospective analysis of the growth kinetics of the bacteria indicated that the bacterial titres were most likely below the diagnostic sensitivity of the BactiFlow assay (screening of platelet concentrates independently of the testing day and the screening strategy. Although the optimal screening strategy could not be defined, this study provides further data to help achieve this goal.

  18. Dynamics of bouncing droplets in annular cavities

    Science.gov (United States)

    Lentz, Zachary Louis; Jalali, Mir Abbas; Alam, Mohammad-Reza

    2014-11-01

    In a cylindrical bath of silicon oil, vertically excited by a frequency of 45 Hz, we trace the motion of bouncing droplets as they fill an annular region. We compute the mean tangential and radial velocity components of the droplets and show that the maximum tangential velocity is larger than the maximum radial velocity by one order of magnitude. Velocity dispersions have almost equal levels in the radial and tangential directions, and their mean values are 1/4 times smaller than the mean tangential velocity. These results show that bouncing droplets undergo random motions within annular cavities determined by the interference patterns of self-induced circumferential waves. We derive analytical relations between the velocity dispersion and the wavelength of surface waves, and calculate the mean tangential velocity of droplets using the random kicks that they experience at the boundaries of the cavity by inward and outward traveling waves.

  19. Quantitative evaluation of concentrated flow erosion in a Mediterranean olive orchard microcatchment

    Science.gov (United States)

    Rebolledo, J.; Taguas, E. V.; Vanwalleghem, T.; Ayuso, J. L.; Gómez, J. A.

    2012-04-01

    Erosion due to rills, ephemeral gullies and gullies in cultivated areas in the Mediterranean area is known to contribute significantly to global soil loss and is one of the major processes of land degradation. This contribution may vary considerably according to the spatial scale, temporal scale and environmental controls, such as soil type, land use, climate and topography (Poesen et al., 2003). For instance, De Santiesteban et al. (2006), working in Navarre in a small catchment with winter cereals over a period of six years, found that ephemeral gullies accounted for 66% of the erosion and for 17% in another small catchment with vineyards over a period of two years. In the case of olive crops, most studies have dealt with quantifying sheet and rill erosion in plots (e.g. Gómez et al., 2008; Gómez et al. 2009). Measurements at larger scales than the plot scale, where the hydrological and erosive processes are more complex and more difficult to evaluate, are rare and data is scarce in the Mediterranean environment (de Vente and Poesen, 2005). Although plot studies and field surveys are essential, it is difficult to extract from them a full picture of the real erosive situation at other scales, especially when the erosive effects of concentrated flow are not measured. This work illustrates some rill features and presents a simple analysis of the contribution of concentrated flow (rills and ephemeral gullies) to the soil losses in an olive orchard microcatchment where tillage operations are usually applied. Rill and ephemeral gullies (shape, depth, width, lenght) formed during an inter-tillage period, were measured and analyzed as well as rainfall characteristics, runoff and sediment load measured in the catchment outlet for the same period (August 2009-March-2010). In the study period, the cumulative rainfall depth and the erosivity were 839 mm and 859.5 MJ Mm ha-1 h-1 respectively, distributed in 30 events. The approximate soil losses in the catchment were 18.7 t

  20. Thermal analysis of a reactive generalized Couette flow of power law fluids between concentric cylindrical pipes

    Science.gov (United States)

    Makinde, O. D.

    2014-12-01

    In this paper, the steady generalized axial Couette flow of Ostwald-de Waele power law reactive fluids between concentric cylindrical pipes is investigated. It is assumed that the outer cylinder is stationary and exchanges heat with the ambient surrounding following Newton's law of cooling, while the inner cylinder with isothermal surface is set in motion in the axial direction. The model nonlinear differential equations for the momentum and energy balance are obtained and tackled numerically using the shooting method coupled with the Runge-Kutta-Fehlberg integration technique. The effects of various embedded thermophysical parameters on the velocity and temperature fields including skin friction, Nusselt number and thermal criticality conditions are presented graphically and discussed quantitatively.

  1. Tangential Velocity Profile for Axial Flow Through Two Concentric Rotating Cylinders with Radial Magnetic Field

    Directory of Open Access Journals (Sweden)

    Girishwar Nath

    1970-10-01

    Full Text Available A closed form solution of the Navier-Stokes equations has been obtained in the case of steady axisymmetric flow of an incompressible electrically conducting viscous fluid between two concentric rotating cylinders composed of an insulating material under the influence of radial magnetic field. It has been found that the velocity components are less than those of the classical hydrodynamic case. In the presence of the magnetic field, the tangential velocity becomes fully developed in a smaller axial distance than in the absence of the magnetic field. For small Reynolds number, the fully developed tangential velocity is achieved in a small axial distance, but it requires greater axial distance for large Reynolds number.

  2. Numerical Analysis of General Trends in Single-Phase Natural Circulation in a 2D-Annular Loop

    Directory of Open Access Journals (Sweden)

    Gilles Desrayaud

    2008-01-01

    Full Text Available The aim of this paper is to address fluid flow behavior of natural circulation in a 2D-annular loop filled with water. A two-dimensional, numerical analysis of natural convection in a 2D-annular closed-loop thermosyphon has been performed for various radius ratios from 1.2 to 2.0, the loop being heated at a constant flux over the bottom half and cooled at a constant temperature over the top half. It has been numerically shown that natural convection in a 2D-annular closed-loop thermosyphon is capable of showing pseudoconductive regime at pitchfork bifurcation, stationary convective regimes without and with recirculating regions occurring at the entrance of the exchangers, oscillatory convection at Hopf bifurcation and Lorenz-like chaotic flow. The complexity of the dynamic properties experimentally encountered in toroidal or rectangular loops is thus also found here.

  3. Annular and Total Solar Eclipses of 2003

    Science.gov (United States)

    Espenak, Fred; Anderson, Jay

    2002-01-01

    On Saturday, 2003 May 31, an annular eclipse of the Sun will be visible from a broad corridor that traverses the North Atlantic. The path of the Moon's antumbral shadow begins in northern Scotland, crosses Iceland and central Greenland, and ends at sunrise in Baffin Bay (Canada). A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes most of Europe, the Middle East, central and northern Asia, and northwestern North America. The trajectory of the Moon's shadow is quite unusual during this event. The shadow axis passes to the far north where it barely grazes Earth's surface. In fact, the northern edge of the antumbra actually misses Earth so that one path limit is defined by the day/night terminator rather than by the shadow's upper edge. As a result, the track of annularity has a peculiar "D" shape that is nearly 1200 kilometers wide. Since the eclipse occurs just three weeks prior to the northern summer solstice, Earth's northern axis is pointed sunwards by 22.8 deg. As seen from the Sun, the antumbral shadow actually passes between the North Pole and the terminator. As a consequence of this extraordinary geometry, the path of annularity runs from east to west rather than the more typical west to east. The event transpires near the Moon's ascending node in Taurus five degrees north of Aldebaran. Since apogee occurs three days earlier (May 28 at 13 UT), the Moon's apparent diameter (29.6 arc-minutes) is still too small to completely cover the Sun (31.6 arc-minutes) resulting in an annular eclipse.

  4. Investigating the effects of transport on the preservation of soft-bodied organisms using an annular flume tank.

    Science.gov (United States)

    Bath Enright, Orla; Minter, Nicholas; Sumner, Esther; Mángano, Gabriela; Buatois, Luis

    2016-04-01

    Annular flume tank experiments offer unique opportunities to be able to investigate the effect of transport on a range of organisms; being able to create slow to fast sediment-laden flows that can be laminar to fully turbulent, and lasting over durations of minutes to hours. Understanding the effects of transport on the preservation potential of different organisms is fundamental to the study of palaeoecology. Despite this, the sedimentological processes leading up to fossil entombment remain largely overlooked. This is especially significant for fossil lagerstätte such as the Burgess Shale, whose exquisite fossil preservation has enabled insights into the anatomy of early soft-bodied organisms and their evolution during the Cambrian explosion. However there is still a fundamental debate with regards to the transport these organisms have undergone. Namely, whether they were living within or close to the environment of deposition, or could they have been transported from one environment to another? As such, does the Burgess Shale biota represent a palaeocommunity or not? To explore the limits of the effect of transport, initial experiments have been designed using an annular flume tank in order to test the influence of fully turbulent sandy suspensions (75-250μm) on organism preservation. This is a three factorial design where the three independent variables are transport duration, sediment concentration and grain angularity. In all experiments, flow velocity was kept constant along with controls on pH and salinity. The dependent variable, an index of "increasing state of damage" has been devised to classify the amount of destruction each organism exhibits after the experimental procedure. Results are presented here. From observations such as these, we can begin to set constraints on the amount of transport, if any, that these fossil organisms could have endured.

  5. Two dimensional analysis of low pressure flows in the annulus region between two concentric cylinders.

    Science.gov (United States)

    Al-Kouz, Wael; Alshare, Aiman; Alkhalidi, Ammar; Kiwan, Suhil

    2016-01-01

    A numerical simulation of the steady two-dimensional laminar natural convection heat transfer for the gaseous low-pressure flows in the annulus region between two concentric horizontal cylinders is carried out. This type of flow occurs in "evacuated" solar collectors and in the receivers of the solar parabolic trough collectors. A finite volume code is used to solve the coupled set of governing equations. Boussinesq approximation is utilized to model the buoyancy effect. A correlation for the thermal conductivity ratio (k r = k eff/k) in terms of Knudsen number and the modified Rayleigh number is proposed for Prandtl number (Pr = 0.701). It is found that as Knudsen number increases then the thermal conductivity ratio decreases for a given Rayleigh number. Also, it is shown that the thermal conductivity ratio k r increases as Rayleigh number increases. It appears that there is no consistent trend for varying the dimensionless gap spacing between the inner and the outer cylinder ([Formula: see text]) on the thermal conductivity ratio (k r) for the considered spacing range.

  6. In situ characterization by SAXS of concentration polarization layers during cross-flow ultrafiltration of Laponite dispersions.

    Science.gov (United States)

    Pignon, F; Abyan, M; David, C; Magnin, A; Sztucki, M

    2012-01-17

    The structural organization inside the concentration polarization layer during cross-flow membrane separation process of Laponite colloidal dispersions has been characterized for the first time by in situ time-resolved small-angle X-ray scattering (SAXS). Thanks to the development of new "SAXS cross-flow filtration cells", concentration profiles have been measured as a function of the distance z from the membrane surface with 50 μm accuracy and linked to the permeation flux, cross-flow, and transmembrane pressure registered simultaneously. Different rheological behaviors (thixotropic gel with a yield stress or shear thinning sol) have been explored by controlling the mutual interactions between the particles as a result on the addition of peptizer. The structural reversibility of the concentration polarization layer has been demonstrated being in agreement with permeation flux measurements. These observations were related to structure of the dispersions under flow and their osmotic pressure.

  7. Nanoporous separator and low fuel concentration to minimize crossover in direct methanol laminar flow fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Hollinger, A.S. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 Green Street, Urbana, IL 61801 (United States); Maloney, R.J.; Jayashree, R.S. [Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Matthews Avenue, Urbana, IL 61801 (United States); Natarajan, D.; Markoski, L.J. [INI Power Systems, 175 Southport Drive, Suite 100, Morrisville, NC 27560 (United States); Kenis, P.J.A. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 Green Street, Urbana, IL 61801 (United States); Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Matthews Avenue, Urbana, IL 61801 (United States)

    2010-06-01

    Laminar flow fuel cells (LFFCs) overcome some key issues - most notably fuel crossover and water management - that typically hamper conventional polymer electrolyte-based fuel cells. Here we report two methods to further minimize fuel crossover in LFFCs: (i) reducing the cross-sectional area between the fuel and electrolyte streams, and (ii) reducing the driving force of fuel crossover, i.e. the fuel concentration gradient. First, we integrated a nanoporous tracketch separator at the interface of the fuel and electrolyte streams in a single-channel LFFC to dramatically reduce the cross-sectional area across which methanol can diffuse. Maximum power densities of 48 and 70 mW cm{sup -2} were obtained without and with a separator, respectively, when using 1 M methanol. This simple design improvement reduces losses at the cathode leading to better performance and enables thinner cells, which is attractive in portable applications. Second, we demonstrated a multichannel cell that utilizes low methanol concentrations (<300 mM) to reduce the driving force for methanol diffusion to the cathode. Using 125 mM methanol as the fuel, a maximum power density of 90 mW cm{sup -2} was obtained. This multichannel cell further simplifies the LFFC design (one stream only) and its operation, thereby extending its potential for commercial application. (author)

  8. Carotenoids concentration of Gac (Momordica cochinchinensis Spreng.) fruit oil using cross-flow filtration technology.

    Science.gov (United States)

    Mai, Huỳnh Cang; Truong, Vinh; Debaste, Frédéric

    2014-11-01

    Gac (Momordica cochinchinensis Spreng.) fruit, a traditional fruit in Vietnam and other countries of eastern Asia, contains an oil rich in carotenoids, especially lycopene and β-carotene. Carotenoids in gac fruit oil were concentrated using cross-flow filtration. In total recycle mode, effect of membrane pore size, temperature, and transmembrane pressure (TMP) on permeate flux and on retention coefficients has been exploited. Resistance of membrane, polarization concentration, and fouling were also analyzed. Optimum conditions for a high permeate flux and a good carotenoids retention are 5 nm, 2 bars, and 40 °C of membrane pore size, TMP, and temperature, respectively. In batch mode, retentate was analyzed through index of acid, phospholipids, total carotenoids content (TCC), total antioxidant activity, total soluble solids, total solid content, color measurement, and viscosity. TCC in retentate is higher 8.6 times than that in feeding oil. Lipophilic antioxidant activities increase 6.8 times, while hydrophilic antioxidant activities reduce 40%. The major part of total resistance is due to polarization (55%) while fouling and intrinsic membrane contribute about 30% and 24%, respectively. © 2014 Institute of Food Technologists®

  9. Gas turbine structural mounting arrangement between combustion gas duct annular chamber and turbine vane carrier

    Energy Technology Data Exchange (ETDEWEB)

    Wiebe, David J.; Charron, Richard C.; Morrison, Jay A.

    2016-10-18

    A gas turbine engine ducting arrangement (10), including: an annular chamber (14) configured to receive a plurality of discrete flows of combustion gases originating in respective can combustors and to deliver the discrete flows to a turbine inlet annulus, wherein the annular chamber includes an inner diameter (52) and an outer diameter (60); an outer diameter mounting arrangement (34) configured to permit relative radial movement and to prevent relative axial and circumferential movement between the outer diameter and a turbine vane carrier (20); and an inner diameter mounting arrangement (36) including a bracket (64) secured to the turbine vane carrier, wherein the bracket is configured to permit the inner diameter to move radially with the outer diameter and prevent axial deflection of the inner diameter with respect to the outer diameter.

  10. Design of a small Annular Linear Induction Electromagnetic Pump - Simulation and Experiment

    OpenAIRE

    Yong-Lin, Ma; Yan-Jiang, Chen; Tao, Jiang; Shu-Qing, Xing

    2015-01-01

    International audience; An annular linear induction electromagnetic pump (ALIP) is used for pumping liquid tin alloy with a flow rate and developed pressure of 17l /min and 0.5bar respectively. The electromagnetic force, flux density and inducted current density are calculated using a by finite element method (FEM) the various design variables. The performance of ALIP is tested with liquid tin for various melting point temperatures. Results show that pressure increases as electromagnetic forc...

  11. Effect of gas diffusion layer and membrane properties in an annular proton exchange membrane fuel cell

    Science.gov (United States)

    Khazaee, I.; Ghazikhani, M.; Esfahani, M. Nasr

    2012-01-01

    A complete three-dimensional and single phase computational dynamics model for annular proton exchange membrane (PEM) fuel cell is used to investigate the effect of changing gas diffusion layer and membrane properties on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the two-dimensional mass, momentum and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC that cannot be investigated experimentally. The results show that by increasing the thickness and decreasing the porosity of GDL the performance of the cell enhances that it is different with planner PEM fuel cell. Also the results show that by decreasing the thickness of the membrane the performance of the cell increases.

  12. Limited Diffraction Maps for Pulsed Wave Annular Arrays

    OpenAIRE

    Fox, Paul D.

    2002-01-01

    A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained. Numerical examples are given in the context of a 10-ring annular array operating at a central frequency of 2.5 MHz in water.

  13. Monitoring of surface velocity of hyper-concentrated flow in a laboratory flume by means of fully-digital PIV

    Science.gov (United States)

    Termini, Donatella; Di Leonardo, Alice

    2016-04-01

    High flow conditions, which are generally characterized by high sediment concentrations, do not permit the use of traditional measurement equipment. Traditional techniques usually are based on the intrusive measure of the vertical profile of flow velocity and on the linking of water depth with the discharge through the rating curve. The major disadvantage of these measurement techniques is that they are difficult to use and not safe for operators especially in high flow conditions. The point is that, as literature shows (see as an example Moramarco and Termini, 2015), especially in such conditions, the measurement of surface velocity distribution is important to evaluate the mean flow velocity and, thus, the flow discharge. In the last decade, image-based techniques have been increasingly used for surface velocity measurements (among others Joeau et al., 2008). Experimental program has been recently conducted at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Materials Engineering (DICAM) - University of Palermo (Italy) in order to analyze the propagation phenomenon of hyper-concentrated flow in a defense channel. The experimental apparatus includes a high-precision camera and a system allowing the images recording. This paper investigates the utility and the efficiency of the digital image-technique for remote monitoring of surface velocity in hyper-concentrated flow by the aid of data collected during experiments conducted in the laboratory flume. In particular the present paper attention is focused on the estimation procedure of the velocity vectors and on their sensitivity with parameters (number of images, spatial resolution of interrogation area,) of the images processing procedure. References Jodeau M., A. Hauet, A. Paquier, Le Coz J., Dramais G., Application and evaluation of LS-PIV technique for the monitoring of river surface in high flow conditions, Flow Measurements and Instrumentation, Vol.19, No.2, 2008, pp.117

  14. Experimental critical parameters of enriched uranium solution in annular tank geometries

    Energy Technology Data Exchange (ETDEWEB)

    Rothe, R.E.

    1996-04-01

    A total of 61 critical configurations are reported for experiments involving various combinations of annular tanks into which enriched uranium solution was pumped. These experiments were performed at two widely separated times in the 1980s under two programs at the Rocky Flats Plant`s Critical Mass Laboratory. The uranyl nitrate solution contained about 370 g of uranium per liter, but this concentration varied a little over the duration of the studies. The uranium was enriched to about 93% [sup 235]U. All tanks were typical of sizes commonly found in nuclear production plants. They were about 2 m tall and ranged in diameter from 0.6 m to 1.5 m. Annular thicknesses and conditions of neutron reflection, moderation, and absorption were such that criticality would be achieved with these dimensions. Only 13 of the entire set of 74 experiments proved to be subcritical when tanks were completely filled with solution. Single tanks of several radial thicknesses were studied as well as small line arrays (1 x 2 and 1 x 3) of annular tanks. Many systems were reflected on four sides and the bottom by concrete, but none were reflected from above. Many experiments also contained materials within and outside the annular regions that contained strong neutron absorbers. One program had such a thick external moderator/absorber combination that no reflector was used at all.

  15. Optical monitoring of the concentration profile of submicron latex particles in flow through a translucent water-permeable tube: demonstration of flow-dependent concentration polarization of plasma proteins at a blood/endothelium boundary

    Science.gov (United States)

    Wada, Shigeo; Iwai, Toshiaki; Karino, Takeshi

    1999-05-01

    It is well accepted that hemodynamics plays an important role in atherogenesis in man. However, the precise mechanisms have not been elucidated yet. Recently, Karino and his coworkers hypothesized that flow-dependent concentration polarization of low-density lipoproteins (LDL: a carrier of cholesterol) may occur at a blood/endothelium boundary, leading to a high risk of atherogenesis in regions of slow flow and low wall shear rate where the concentration of LDL builds up. In this study, we attempted to confirm experimentally their predictions by measuring optically the concentration profile of polystyrene microspheres (used as a model of LDL) flowing in steady flow through a dialyses tube (used as a model of an artery) by transversing a laser beam across the tube and detecting the intensity of the transmitted light. It was found that surface concentration of the microsphere certainly increases with decreasing the flow rate (hence wall shear rate) and it occurs even under the conditions of a very low water filtration velocity encountered in normal arteries in vivo, thus giving a strong support to the hypothesis proposed by Karino et al.

  16. Granuloma annulare localized to the shaft of the penis

    DEFF Research Database (Denmark)

    Trap, R; Wiebe, B

    1993-01-01

    A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis.......A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis....

  17. Arcuate, annular, and polycyclic inflammatory and infectious lesions.

    Science.gov (United States)

    Sharma, Amit; Lambert, Phelps J; Maghari, Amin; Lambert, W Clark

    2011-01-01

    Common shapes encountered in dermatologic diseases include linear, nummular, annular, polycyclic, and arciform. The last three have a relatively restricted differential, which must be entirely explored. It is not uncommon for a single disease to present in annular, arciform or polycyclic configurations; moreover, the lesions may evolve from being arciform to annular and then become polycyclic. Regardless, recognizing the arrangement of the defect will undoubtedly help in making a diagnosis and guiding subsequent management. We explore diseases that often present in annular, arciform, and/or polycyclic forms.

  18. Granuloma annulare localized to the shaft of the penis

    DEFF Research Database (Denmark)

    Trap, R; Wiebe, B

    1993-01-01

    A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis.......A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis....

  19. Determining concentration fields of tracer plumes for layered porous media in flow-tank experiments

    Science.gov (United States)

    Yu, Zhongbo; Schwartz, Franklin W.

    In the laboratory, computer-assisted image analysis provides an accurate and efficient way to monitor tracer experiments. This paper describes the determination of detailed temporal concentration distributions of tracers in a flow-tank experiment by analyzing photographs of plumes of Rhodamine dye through the glass wall of the tank. The methodology developed for this purpose consists of four steps: (1) digitally scanning black and white negatives obtained from photographs of the flow-tank experiment; (2) calibrating and normalizing each digitized image to a standard optical-density scale by determining the relation between the optical density and pixel value for each image; (3) constructing standard curves relating the concentration in an optical density from five experimental runs with predetermined concentrations (2-97mg/L) and (4) converting the optical density to concentration. The spatial distribution of concentration for two photographs was determined by applying these calibration and conversion procedures to all pixels of the digitized images. This approach provides an efficient way to study patterns of plume evolution and transport mechanisms. Résumé Au laboratoire, l'analyse d'images assistée par ordinateur est un moyen précis et efficace pour suivre certaines expériences de traçage. Ce papier présente comment sont déterminées dans le détail les distributions temporelles de la concentration en traceur au cours d'une expérience d'écoulement en réservoir au moyen de l'analyse de photographies de panaches de rhodamine à travers la paroi de verre du réservoir. La méthodologie développée dans cette expérience suit quatre étapes: (1) digitalisation par balayage des négatifs noir et blanc des prises de vue de l'expérience d'écoulement en réservoir (2) calibration et normalisation de chaque image digitalisée par rapport à une échelle étalon de densité optique en déterminant la relation entre la densité optique et la valeur des pixels

  20. Comparison of instruments for investigation of microcirculatory blood flow and red blood cell concentration

    Science.gov (United States)

    O'Doherty, Jim; McNamara, Paul; Clancy, Neil T.; Enfield, Joey G.; Leahy, Martin J.

    2009-05-01

    The use of laser Doppler perfusion imaging (LDPI) and laser speckle perfusion imaging (LSPI) is well known in the noninvasive investigation of microcirculatory blood flow. This work compares the two techniques with the recently developed tissue viability (TiVi) imaging system, which is proposed as a useful tool to quantify red blood cell concentration in microcirculation. Three systems are evaluated with common skin tests such as the use of vasodilating and vasoconstricting drugs (methlynicotinate and clobetasol, respectively) and a reactive hyperaemia maneuver (using a sphygmomanometer). The devices investigated are the laser Doppler line scanner (LDLS), the laser speckle perfusion imager (FLPI)-both from Moor Instruments (Axminster, United Kingdom)-and the TiVi imaging system (WheelsBridge AB, Linköping, Sweden). Both imaging and point scanning by the devices are used to quantify the provoked reactions. Perfusion images of vasodilatation and vasoconstriction are acquired with both LDLS and FLPI, while TiVi images are acquired with the TiVi imager. Time acquisitions of an averaged region of interest are acquired for temporal studies such as the reactive hyperaemia. In contrast to the change in perfusion over time with pressure, the TiVi imager shows a different response due its measurement of blood concentration rather than perfusion. The responses can be explained by physiological understanding. Although the three devices sample different compartments of tissue, and output essentially different variables, comparisons can be seen between the three systems. The LDLS system proves to be suited to measurement of perfusion in deeper vessels, while FLPI and TiVi showed sensitivity to more superficial nutritional supply. LDLS and FLPI are insensitive to the action of the vasoconstrictor, while TiVi shows the clear boundaries of the reaction. Assessment of the resolution, penetration depth, and acquisition rate of each instrument show complimentary features that should

  1. Experimental investigation of gas turbine airfoil aerodynamic performance without and with film cooling in an annular sector cascade

    Energy Technology Data Exchange (ETDEWEB)

    Wiers, S.H.

    2002-02-01

    The steady growing of industrialization, the densification of the anthroposphere, the increasing concern over the effects of gas turbine cruise emissions on the atmosphere threaten the growth of air transportation, and the perception about the possible climatic impact of CO{sub 2} emissions causes a public distinctive sense of responsibility. The conventional energy production techniques, which are based on fossil fuel, will keep its central importance within the global energy production. Forecasts about the increasing air transportation give duplication in the next 10-15 years. The optimization of the specific fuel consumption is necessary to decrease the running costs and the pollution emissions in the atmosphere, which makes an increased process efficiency of stationary turbines as well as of jet engines essential. This leads to the necessity of an increased thermodynamic efficiency of the overall process and the optimization of the aerodynamic components. Due to the necessity of more detailed three-dimensional data on the behavior of film cooled blades an annular sector cascade turbine test facility has gone into service. The annular sector cascade facility is a relative cost efficient solution compared to a full annular facility to investigate three-dimensional effects on a non cooled and cooled turbine blade. The aerodynamic investigations on the annular sector cascade facility are part of a broad perspective where experimental data from a hot annular sector cascade facility and the cold annular sector facility are used to verify, calibrate and understand the physics for both internal and external calculation methods for flow and heat transfer prediction. The objective of the present study is the design and validation of a cold flow annular sector cascade facility, which meets the flow conditions in a modem turbine as close as possible, with emphasis on achieving periodic flow conditions. The first part of this study gives the necessary background on this

  2. An analytic solution and investigation of character of viscoelastic fluids in double-gap concentric cylinder rheometer

    Institute of Scientific and Technical Information of China (English)

    黄军旗; 刘慈群

    1995-01-01

    An analytical solution to annular pipe flow of the second fluid and Maxwell fluid is given using Weber integral transform. The formulas can be used to analyse the behavior of unsteady flow of viscoelastic fluid in annular pipe, especially to analyse the flow character of double-gap concentric cylinder rheometer. It is found by computation that when the outer cylinder is in simple periodic motion, there are step junctions along the history curve of Maxwell fluid’s velocity and shear stress, and at step junctions both amplitude and phase of oscillatory wave vary sharply; when the outer cylinder makes uniform rotation, the velocity and shear stress of Maxwell fluid exhibit rhombic wave oscillation, and its period is in close parabolic relation with material constant H.

  3. Use of horizontal subsurface flow constructed wetlands to treat reverse osmosis concentrate of rolling wastewater.

    Science.gov (United States)

    Xu, Jingcheng; Zhao, Gang; Huang, Xiangfeng; Guo, Haobo; Liu, Wei

    2017-03-04

    According to the characteristics of the reverse osmosis concentrate (ROC) generated from iron and steel company, we used three sets of parallel horizontal subsurface flow (HSF) constructed wetlands (CWs) with different plants and substrate layouts to treat the high-salinity wastewater. The plant growth and removal efficiencies under saline condition were evaluated. The evaluation was based entirely on routinely collected water quality data and the physical and chemical characteristics of the plants (Phragmites australis, Typha latifolia, Iris wilsonii, and Scirpus planiculmis). The principal parameters of concern in the effluent were chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP). The results showed that the CWs were able to remove COD, TN, and TP from ROC. S. planiculmis was not suitable for the treatment of high-saline wastewater. The sequence of metals accumulated in CW plants was K>Ca>Na>Mg>Zn>Cu. More than 70% of metals were accumulated in the aboveground of P. australis. The CW filled with gravel and manganese ore and planted with P. australis and T. latifolia had the best performance of pollutant removal, with average removal of 49.96%, 39.45%, and 72.01% for COD, TN, and TP, respectively. The effluent water quality met the regulation in China. These results suggested that HSF CW planted with P. australis and T. latifolia can be applied for ROC pollutants removal.

  4. Perceived enjoyment, concentration, intention, and speed violation behavior: Using flow theory and theory of planned behavior.

    Science.gov (United States)

    Atombo, Charles; Wu, Chaozhong; Zhang, Hui; Wemegah, Tina D

    2017-10-03

    Road accidents are an important public health concern, and speeding is a major contributor. Although flow theory (FLT) is a valid model for understanding behavior, currently the nature of the roles and interplay of FLT constructs within the theory of planned behavior (TPB) framework when attempting to explain the determinants of motivations for intention to speed and speeding behavior of car drivers is not yet known. The study aims to synthesize TPB and FLT in explaining drivers of advanced vehicles intentions to speed and speed violation behaviors and evaluate factors that are critical for explaining intention and behavior. The hypothesized model was validated using a sample collected from 354 fully licensed drivers of advanced vehicles, involving 278 males and 76 females on 2 occasions separated by a 3-month interval. During the first of the 2 occasions, participants completed questionnaire measures of TPB and FLT variables. Three months later, participants' speed violation behaviors were assessed. The study observed a significant positive relationship between the constructs. The proposed model accounted for 51 and 45% of the variance in intention to speed and speed violation behavior, respectively. The independent predictors of intention were enjoyment, attitude, and subjective norm. The independent predictors of speed violation behavior were enjoyment, concentration, intention, and perceived behavioral control. The findings suggest that safety interventions for preventing speed violation behaviors should be aimed at underlying beliefs influencing the speeding behaviors of drivers of advanced vehicles. Furthermore, perceived enjoyment is of equal importance to driver's intention, influencing speed violation behavior.

  5. Annular lupus vulgaris mimicking tinea cruris.

    Science.gov (United States)

    Heo, Young Soo; Shin, Won Woong; Kim, Yong Ju; Song, Hae Jun; Oh, Chil Hwan

    2010-05-01

    Cutaneous tuberculosis is an infrequent form of extrapulmonary tuberculosis. It is often clinically and histopathologically confused with various cutaneous disorders. A 36-year-old man attended our clinic with slowly progressive, asymptomatic, annular skin lesions on both the thighs and buttocks for 10 years. He consulted with many physicians and was improperly treated with an oral antifungal agent for several months under the diagnosis of tinea cruris, but no resolution of his condition was observed. A diagnosis of lupus vulgaris was made based on the histopathologic examination and the polymerase chain reaction assay. Anti-tuberculosis therapy was administered and the lesions started to regress.

  6. Wave turbulence in annular wave tank

    Science.gov (United States)

    Onorato, Miguel; Stramignoni, Ettore

    2014-05-01

    We perform experiments in an annular wind wave tank at the Dipartimento di Fisica, Universita' di Torino. The external diameter of the tank is 5 meters while the internal one is 1 meter. The tank is equipped by two air fans which can lead to a wind of maximum 5 m/s. The present set up is capable of studying the generation of waves and the development of wind wave spectra for large duration. We have performed different tests including different wind speeds. For large wind speed we observe the formation of spectra consistent with Kolmogorv-Zakharov predictions.

  7. Annular Lupus Vulgaris Mimicking Tinea Cruris

    Science.gov (United States)

    Heo, Young Soo; Shin, Won Woong; Kim, Yong Ju; Song, Hae Jun

    2010-01-01

    Cutaneous tuberculosis is an infrequent form of extrapulmonary tuberculosis. It is often clinically and histopathologically confused with various cutaneous disorders. A 36-year-old man attended our clinic with slowly progressive, asymptomatic, annular skin lesions on both the thighs and buttocks for 10 years. He consulted with many physicians and was improperly treated with an oral antifungal agent for several months under the diagnosis of tinea cruris, but no resolution of his condition was observed. A diagnosis of lupus vulgaris was made based on the histopathologic examination and the polymerase chain reaction assay. Anti-tuberculosis therapy was administered and the lesions started to regress. PMID:20548922

  8. Tank evaluation system shielded annular tank application

    Energy Technology Data Exchange (ETDEWEB)

    Freier, D.A.

    1988-10-04

    TEST (Tank Evaluation SysTem) is a research project utilizing neutron interrogation techniques to analyze the content of nuclear poisons and moderators in tank shielding. TEST experiments were performed on an experimental SAT (Shielded Annular Tank) at the Rocky Flats Plant. The purpose of these experiments was threefold: (1) to assess TEST application to SATs, (2) to determine if Nuclear Safety inspection criteria could be met, and (3) to perform a preliminary calibration of TEST for SATs. Several experiments were performed, including measurements of 11 tank shielding configurations, source-simulated holdup experiments, analysis of three detector modes, resolution studies, and TEST scanner geometry experiments. 1 ref., 21 figs., 4 tabs.

  9. Finite stretching of an annular plate.

    Science.gov (United States)

    Biricikoglu, V.; Kalnins, A.

    1971-01-01

    The problem of the finite stretching of an annular plate which is bonded to a rigid inclusion at its inner edge is considered. The material is assumed to be isotropic and incompressible with a Mooney-type constitutive law. It is shown that the inclusion of the effect of the transverse normal strain leads to a rapid variation in thickness which is confined to a narrow edge zone. The explicit solutions to the boundary layer equations, which govern the behavior of the plate near the edges, are presented.

  10. Flow speed alters the apparent size and concentration of particles measured using NanoSight nanoparticle tracking analysis.

    Science.gov (United States)

    Tong, M; Brown, O S; Stone, P R; Cree, L M; Chamley, L W

    2016-02-01

    Nanoparticle tracking analysis (NTA) is commonly used to count and size nano-sized particles. A sample loading pump can be used to analyse a larger sample volume, but it is unclear whether accuracy is affected. Using a NanoSight NS300 with the manufacturer-supplied pump, we examined synthetic silica and latex microspheres, liposomes and placental extracellular vesicles at different flow speeds. Analysis at flow speeds of 20 or 50 significantly reduced the measured concentration and mean/modal size of particles, particularly for mono-dispersed samples. We identify sample flow speed as a crucial instrument setting which should be reported in all studies that use NTA.

  11. Annular and semicircular lipoatrophies. Report of three cases and review of the literature.

    Science.gov (United States)

    Rongioletti, F; Rebora, A

    1989-03-01

    Two cases of semicircular lipoatrophy and one of annular lipoatrophy are presented. The reasons why semicircular lipoatrophy, annular lipoatrophy, and annular atrophy of the ankles seem to be different clinical entities are discussed.

  12. The Hydraulic Test Report for Non-instrumented Irradiation Test Rig of DUO-Cooled Annular Pellet

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae Ho; Lee, Kang Hee; Shin, Chang Hwan; Yang, Yong Sik; Kim, Sun Ki; Bang, Je Geon; Song, Kun Woo

    2007-08-15

    This report presents the results of pressure drop test and vibration test for non-instrumented rig of Advanced PWR DUO-Fuel Annular Pellet which were designed and fabricated by KAERI. From the pressure drop test results, it is noted that the flow velocity across the non-instrumented rig of Advanced PWR DUO-Fuel Annular Pellet corresponding to the pressure drop of 200 kPa is measured to be about 8.30 kg/sec. Vibration frequency results for the non-instrumented rig at the pump spin frequency ranges from 19.0 to 32.0 Hz, RMS(Root Mean Square) displacement for the non-instrumented rig of Advanced PWR DUO-Fuel Annular Pellet is less than 7.25 m, and the maximum displacement is less than 31.27 {mu}m. This test was performed at the FIVPET facility.

  13. 液层厚度比对环形腔内双层液体的热毛细对流稳定性的影响%Influence of liquid layer depth ratio on stability of thermocapillary flow in annular two-layer system with upper rigid wall

    Institute of Scientific and Technical Information of China (English)

    莫东鸣

    2015-01-01

    In order to understand the liquid layer depth ratio on the stability of two-layer system with upper rigid walls at the microgravity condition,a linear stability analysis of thermocapillary flow in the annular immiscible two-layer system of 5cSt silicone oil and HT-70 was carried out using Implicity Restarted Arnoldi Method (IRAM).Critical values of Marangoni number,wave number and phase velocity were obtained at different liquid layer depth ratios,different aspect ratios of the cavity and different radius rations.The thermofluid wave pattern at the liquid-liquid interface near the critical Marangoni number was also exhibited.%为了了解微重力条件下、水平温度梯度作用时,上部为固壁的环形腔内双层流体系统中液层厚度比对流动稳定性的影响,采用隐式重启 Arnoldi方法(IRAM)对环形池内5cSt 硅油/HT-70双层流体的热对流过程进行了线性稳定性分析,获得了不同液层厚度比下系统流动的临界 Marangoni 数、临界波数、临界相速度,并通过计算特征向量,得到了临界 Marangoni数附近液-液界面的热流体波形态。

  14. Experimental study on structural optimization of a supercritical circulating fluidized bed boiler with an annular furnace and six cyclones

    Science.gov (United States)

    Wang, Xiaofang; Shuai, Daping; Lyu, Qinggang

    2017-10-01

    Annular furnace CFBs with six cyclones represent new designs for large capacity CFB boilers over 660 MW. To investigate the gas-solid flow non-uniformity and its main influencing factors, an experimental study was carried out in the cold-test rig of an annular furnace CFB with six cyclones. The influence of furnace structure and cyclone arrangement on the non-uniformity of gas-solid flow was obtained. On the basis of these findings, the structure of the annular furnace CFB with six cyclones was optimized, and an optimal structure was obtained. The results show that for newly designed annular furnace CFBs, the non-uniformity of gas-solid flow among loops is no greater than that of traditional CFBs. In terms of uniformity, side cyclones rotating inward are superior to those rotating outward. The position of the side cyclones determines the basic solid circulating rate distribution trend and can dramatically improve flow non-uniformity. The middle cyclone positions and the symmetric modes of the cyclones do not determine the solid circulating rate distribution trend and have less effect on DEV Gs. Forty-five degree chamfers of outer ring walls can reduce wall erosion and the non-uniformity of gas-solid flow in the circulating fluidized bed. Regarding the operating and structural conditions in this work, the optimal structure of annular furnace CFBs is Type 6: side cyclones rotating inward and b = a/2, d = 0.1 c; the center of the middle cyclone inlet located at the centerline of the furnace cross-section; cyclones on the two sides of the furnace in an axisymmetric arrangement; and a furnace corner shape of 45° chamfers. Under the given operating conditions, the DEV Gs for the optimal structure are approximately 4.0% 10.3%.

  15. Investigation of empirical correlations on the determination of condensation heat transfer characteristics during downward annular flow of R134a inside a vertical smooth tube using artificial intelligence algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Balcilar, Muhammet; Dalkilic, Ahmet Selim; Bolat, Berna [Yildiz Technical University, Istanbul (Turkmenistan); Wongwises, Somchai [King Mongkut' s University of Technology Thonburi, Bangkok (Thailand)

    2011-10-15

    The heat transfer characteristics of R134a during downward condensation are investigated experimentally and numerically. While the convective heat transfer coefficient, two-phase multiplier and frictional pressure drop are considered to be the significant variables as output for the analysis, inputs of the computational numerical techniques include the important two-phase flow parameters such as equivalent Reynolds number, Prandtl number, Bond number, Froude number, Lockhart and Martinelli number. Genetic algorithm technique (GA), unconstrained nonlinear minimization algorithm-Nelder-Mead method (NM) and non-linear least squares error method (NLS) are applied for the optimization of these significant variables in this study. Regression analysis gave convincing correlations on the prediction of condensation heat transfer characteristics using {+-}30% deviation band for practical applications. The most suitable coefficients of the proposed correlations are depicted to be compatible with the large number of experimental data by means of the computational numerical methods. Validation process of the proposed correlations is accomplished by means of the comparison between the various correlations reported in the literature.

  16. Particle-in-cell simulation of electron trajectories and irradiation uniformity in an annular cathode high current pulsed electron beam source

    Science.gov (United States)

    Jiang, Wei; Wang, Langping; Zhou, Guangxue; Wang, Xiaofeng

    2017-02-01

    In order to study electron trajectories in an annular cathode high current pulsed electron beam (HCPEB) source based on carbon fiber bunches, the transmission process of electrons emitted from the annular cathode was simulated using a particle-in-cell model with Monte Carlo collisions (PIC-MCC). The simulation results show that the intense flow of the electrons emitted from the annular cathode are expanded during the transmission process, and the uniformity of the electron distribution is improved in the transportation process. The irradiation current decreases with the irradiation distance and the pressure, and increases with the negative voltage. In addition, when the irradiation distance and the cathode voltage are larger than 40 mm and -15 kV, respectively, a uniform irradiation current distribution along the circumference of the anode can be obtained. The simulation results show that good irradiation uniformity of circular components can be achieved by this annular cathode HCPEB source.

  17. Multiple paths of electron flow to current in microbial electrolysis cells fed with low and high concentrations of propionate.

    Science.gov (United States)

    Hari, Ananda Rao; Katuri, Krishna P; Gorron, Eduardo; Logan, Bruce E; Saikaly, Pascal E

    2016-07-01

    Microbial electrolysis cells (MECs) provide a viable approach for bioenergy generation from fermentable substrates such as propionate. However, the paths of electron flow during propionate oxidation in the anode of MECs are unknown. Here, the paths of electron flow involved in propionate oxidation in the anode of two-chambered MECs were examined at low (4.5 mM) and high (36 mM) propionate concentrations. Electron mass balances and microbial community analysis revealed that multiple paths of electron flow (via acetate/H2 or acetate/formate) to current could occur simultaneously during propionate oxidation regardless of the concentration tested. Current (57-96 %) was the largest electron sink and methane (0-2.3 %) production was relatively unimportant at both concentrations based on electron balances. At a low propionate concentration, reactors supplemented with 2-bromoethanesulfonate had slightly higher coulombic efficiencies than reactors lacking this methanogenesis inhibitor. However, an opposite trend was observed at high propionate concentration, where reactors supplemented with 2-bromoethanesulfonate had a lower coulombic efficiency and there was a greater percentage of electron loss (23.5 %) to undefined sinks compared to reactors without 2-bromoethanesulfonate (11.2 %). Propionate removal efficiencies were 98 % (low propionate concentration) and 78 % (high propionate concentration). Analysis of 16S rRNA gene pyrosequencing revealed the dominance of sequences most similar to Geobacter sulfurreducens PCA and G. sulfurreducens subsp. ethanolicus. Collectively, these results provide new insights on the paths of electron flow during propionate oxidation in the anode of MECs fed with low and high propionate concentrations.

  18. Unified theory to evaluate the effect of concentration difference and Peclet number on electroosmotic mobility error of micro electroosmotic flow

    KAUST Repository

    Wang, Wentao

    2012-03-01

    Both theoretical analysis and nonlinear 2D numerical simulations are used to study the concentration difference and Peclet number effect on the measurement error of electroosmotic mobility in microchannels. We propose a compact analytical model for this error as a function of normalized concentration difference and Peclet number in micro electroosmotic flow. The analytical predictions of the errors are consistent with the numerical simulations. © 2012 IEEE.

  19. Multiple paths of electron flow to current in microbial electrolysis cells fed with low and high concentrations of propionate

    KAUST Repository

    Rao, Hari Ananda

    2016-03-03

    Microbial electrolysis cells (MECs) provide a viable approach for bioenergy generation from fermentable substrates such as propionate. However, the paths of electron flow during propionate oxidation in the anode of MECs are unknown. Here, the paths of electron flow involved in propionate oxidation in the anode of two-chambered MECs were examined at low (4.5 mM) and high (36 mM) propionate concentrations. Electron mass balances and microbial community analysis revealed that multiple paths of electron flow (via acetate/H2 or acetate/formate) to current could occur simultaneously during propionate oxidation regardless of the concentration tested. Current (57–96 %) was the largest electron sink and methane (0–2.3 %) production was relatively unimportant at both concentrations based on electron balances. At a low propionate concentration, reactors supplemented with 2-bromoethanesulfonate had slightly higher coulombic efficiencies than reactors lacking this methanogenesis inhibitor. However, an opposite trend was observed at high propionate concentration, where reactors supplemented with 2-bromoethanesulfonate had a lower coulombic efficiency and there was a greater percentage of electron loss (23.5 %) to undefined sinks compared to reactors without 2-bromoethanesulfonate (11.2 %). Propionate removal efficiencies were 98 % (low propionate concentration) and 78 % (high propionate concentration). Analysis of 16S rRNA gene pyrosequencing revealed the dominance of sequences most similar to Geobacter sulfurreducens PCA and G. sulfurreducens subsp. ethanolicus. Collectively, these results provide new insights on the paths of electron flow during propionate oxidation in the anode of MECs fed with low and high propionate concentrations.

  20. Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

    OpenAIRE

    Krupička, Jan; Matoušek, Václav

    2014-01-01

    Principles of gamma-ray-based measurement are summarized and their application is demonstrated on an operation of the radiometric facility installed in the test loop for slurry flows at the Institute of Hydrodynamics. The facility is able to measure vertical profiles of chord-averaged concentrations and concentration maps in the pipe cross section. A methodology of measurement is proposed including detection and quantification of random and systematic errors. Experimental results are disc...

  1. Annular and Total Solar Eclipses of 2010

    Science.gov (United States)

    Espenak, Fred; Anderson, J.

    2008-01-01

    While most NASA eclipse bulletins cover a single eclipse, this publication presents predictions for two solar eclipses during 2010. This has required a different organization of the material into the following sections. Section 1 -- Eclipse Predictions: The section consists of a general discussion about the eclipse path maps, Besselian elements, shadow contacts, eclipse path tables, local circumstances tables, and the lunar limb profile. Section 2 -- Annular Solar Eclipse of 2010 Ja n 15: The section covers predictions and weather prospects for the annular eclipse. Section 3 -- Total Solar Eclipse of 2010 Jul 11: The se ction covers predictions and weather prospects for the total eclipse. Section 4 -- Observing Eclipses: The section provides information on eye safety, solar filters, eclipse photography, and making contact timings from the path limits. Section 5 -- Eclipse Resources: The final section contains a number of resources including information on the IAU Working Group on Eclipses, the Solar Eclipse Mailing List, the NASA eclipse bulletins on the Internet, Web sites for the two 2010 eclipses, and a summary identifying the algorithms, ephemerides, and paramete rs used in the eclipse predictions.

  2. Signatures of an annular Fermi sea

    Science.gov (United States)

    Jo, Insun; Liu, Yang; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.; Winkler, R.

    2017-01-01

    The concept of a Fermi surface, the constant-energy surface containing all the occupied electron states in momentum, or wave-vector (k ) , space plays a key role in determining electronic properties of conductors. In two-dimensional (2D) carrier systems, the Fermi surface becomes a contour which, in the simplest case, encircles the occupied states. In this case, the area enclosed by the contour, which we refer to as the Fermi sea (FS), is a simple disk. Here we report the observation of an FS with a new topology, namely, an FS in the shape of an annulus. Such an FS is expected in a variety of 2D systems where the energy band dispersion supports a ring of extrema at finite k , but its experimental observation has been elusive. Our study provides (1) theoretical evidence for the presence of an annular FS in 2D hole systems confined to wide GaAs quantum wells and (2) experimental signatures of the onset of its occupation as an abrupt rise in the sample resistance, accompanied by a sudden appearance of Shubnikov-de Haas oscillations at an unexpectedly high frequency whose value does not simply correspond to the (negligible) density of holes contained within the annular FS.

  3. Limited Diffraction Maps for Pulsed Wave Annular Arrays

    DEFF Research Database (Denmark)

    Fox, Paul D.

    2002-01-01

    A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained...

  4. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume II. Chapters 6-10)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  5. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume III. Chapters 11-14)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  6. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume IV. Chapters 15-19)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  7. Interfacial Area and Interfacial Transfer in Two-Phase Flow Systems (Volume I. Chapters 1-5)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, T.; Park, J.; Kojasoy, G.

    2003-03-15

    Experiments were performed on horizontal air-water bubbly two-phase flow, axial flow, stratified wavy flow, and annular flow. Theoretical studies were also undertaken on interfacial parameters for a horizontal two-phase flow.

  8. Annular core for Modular High-Temperature Gas-Cooled Reactor (MHTGR)

    Energy Technology Data Exchange (ETDEWEB)

    Turner, R.F.; Baxter, A.M.; Stansfield, O.M.; Vollman, R.E.

    1987-08-01

    The active core of the 350 MW(t) MHTGR is annular in configuration, shaped to provide a large external surface-to-volume ratio for the transport of heat radially to the reactor vessel in case of a loss of coolant flow. For a given fuel temperature limit, the annular core provides approximately 40% greater power output over a typical cylindrical configuration. The reactor core is made up of columns of hexagonal blocks, each 793-mm high and 360-mm wide. The active core is 3.5 m in o.d., 1.65 m in i.d., and 7.93-m tall. Fuel elements contain TRISO-coated microspheres of 19.8% enriched uranium oxycarbide and of fertile thorium oxide. The core is controlled by 30 control rods which enter the inner and outer side reflectors from above.

  9. Annular core for the Modular High-Temperature Gas-cooled Reactor (MHTGR)

    Energy Technology Data Exchange (ETDEWEB)

    Turner, R.F.; Baxter, A.M.; Stansfield, O.M.; Vollman, R.E.

    The active core of the 350 MW(t) MHTGR is annular in configuration, shaped to provide a large external surface-to-volume ratio for the transport of heat radially to the reactor vessel in case of a loss of coolant flow. For a given fuel temperature limit, the annular core provides approximately 40% greater power output over a typical cylindrical configuration. The reactor core is made up to columns of hexagonal blocks, each 793 mm high and 360 mm wide. The active core is 3.5 m in outside diameter, 1.65 m in inside diameter, and 7.93 m tall. Fuel elements contain TRISO-coated microspheres of 19.8% enriched uranium oxycarbide and of fertile thorium oxide. The core is controlled by 30 control rods which enter the inner and outer side reflectors from above.

  10. Fabrication of microfluidic architectures for optimal flow rate and concentration measurement for lab on chip application

    Science.gov (United States)

    Adam, Tijjani; Hashim, U.

    2017-03-01

    Optimum flow in micro channel for sensing purpose is challenging. In this study, The optimizations of the fluid sample flows are made through the design and characterization of the novel microfluidics' architectures to achieve the optimal flow rate in the micro channels. The biocompatibility of the Polydimetylsiloxane (Sylgard 184 silicon elastomer) polymer used to fabricate the device offers avenue for the device to be implemented as the universal fluidic delivery system for bio-molecules sensing in various bio-medical applications. The study uses the following methodological approaches, designing a novel microfluidics' architectures by integrating the devices on a single 4 inches silicon substrate, fabricating the designed microfluidic devices using low-cost solution soft lithography technique, characterizing and validating the flow throughput of urine samples in the micro channels by generating pressure gradients through the devices' inlets. The characterization on the urine samples flow in the micro channels have witnessed the constant flow throughout the devices.

  11. Concentration Polarization and Nonequilibrium Electro-osmotic Instability at an Ion-Selective Surface Admitting Normal Flow

    Science.gov (United States)

    Khair, Aditya

    2011-11-01

    We revisit and build upon on the prototypical problem of ion transport across a flat ideal ion-selective surface. Specifically, we examine the influence of imposed fluid flows on concentration polarization (CP) and electrokinetic instability at over-limiting currents. We consider an ion-selective surface, or membrane, that admits a uniform flow across itself. The membrane contacts an electrolyte, whose concentration is uniform in a well-mixed region at a prescribed distance from the membrane. A voltage across the system drives an ionic current, leading to CP in the ``unstirred layer'' between the membrane and well-mixed bulk. The CP reflects a balance between advection of ions with the ``normal flow'' and diffusion. A Peclet number, Pe, parameterizes their relative importance; note, Pe is signed, as the flow can be toward or away from the membrane. An asymptotic analysis for thin Debye layers reveals a nonlinear CP profile, in contrast to the familiar linear profile at Pe=0. Next, we consider over-limiting currents, wherein a non-equilibrium space-charge layer emerges near the membrane surface. Finally, we examine the instability of the quiescent concentration polarization due to second-kind electro-osmosis in the space-charge layer. A stability analysis shows that the imposed normal flow can enhance or retard the instability, depending on its direction.

  12. Effect of annular secondary conductor in a linear electromagnetic stirrer

    Indian Academy of Sciences (India)

    R Madhavan; V Ramanarayanan

    2008-10-01

    This paper presents the variation of average axial force density in the annular secondary conductor of a linear electromagnetic stirrer. Different geometries of secondaries are considered for numerical and experimental validation namely, 1. hollow annular ring, 2. annular ring with a solid cylinder and 3. solid cylinder. Experimental and numerical simulations are performed for a 2-pole in house built 15 kW linear electromagnetic stirrer (EMS). It is observed for a supply current of 200 A at 30 Hz the force densities in the hollow annular ring is 67% higher than the equivalent solid cylinder. The same values are 33% for annular ring with a solid cylinder. Force density variation with supply frequency and current are also reported. Numerical simulations using finite element model are validated with experimental results.

  13. Vortex beam based more stable annular laser guide star

    Science.gov (United States)

    Luo, Ruiyao; Cui, Wenda; Li, Lei; Sun, Quan; He, Yulong; Wang, Hongyan; Ning, Yu; Xu, Xiaojun

    2016-11-01

    We present an annular laser guide star (LGS) concept for large ground-based telescopes in this paper. The more stable annular LGS is generated by turbulence-resisted vortex beam. In the uplink, a vortex beam tends to wander more slightly than a Gaussian beam does in atmospheric turbulence. This may enable an annular LGS to wander more slightly than a traditional Gaussian beam generated LGS does, which would ease the burden of uplink tip-tilt mirror and benefit a dynamical closed-loop adaptive optics system. We conducted numerical simulation to validate the feasibility of this concept. And we have gotten 31% reduced variance of spot wandering of annular LGS. Besides, we set up a spatial light modulator based laser guide star simulator for beam propagation in turbulent atmosphere to experimentally test the annular LGS concept. Preliminary experimental results are given. To the best of our knowledge, it is the first time this concept is formulated.

  14. Microbubble moving in blood flow in microchannels: effect on the cell-free layer and cell local concentration.

    Science.gov (United States)

    Bento, David; Sousa, Lúcia; Yaginuma, Tomoko; Garcia, Valdemar; Lima, Rui; Miranda, João M

    2017-03-01

    Gas embolisms can hinder blood flow and lead to occlusion of the vessels and ischemia. Bubbles in microvessels circulate as tubular bubbles (Taylor bubbles) and can be trapped, blocking the normal flow of blood. To understand how Taylor bubbles flow in microcirculation, in particular, how bubbles disturb the blood flow at the scale of blood cells, experiments were performed in microchannels at a low Capillary number. Bubbles moving with a stream of in vitro blood were filmed with the help of a high-speed camera. Cell-free layers (CFLs) were observed downstream of the bubble, near the microchannel walls and along the centerline, and their thicknesses were quantified. Upstream to the bubble, the cell concentration is higher and CFLs are less clear. While just upstream of the bubble the maximum RBC concentration happens at positions closest to the wall, downstream the maximum is in an intermediate region between the centerline and the wall. Bubbles within microchannels promote complex spatio-temporal variations of the CFL thickness along the microchannel with significant relevance for local rheology and transport processes. The phenomenon is explained by the flow pattern characteristic of low Capillary number flows. Spatio-temporal variations of blood rheology may have an important role in bubble trapping and dislodging.

  15. Relationship between colour flow Doppler sonographic assessment of corpus luteum activity and progesterone concentrations in mares after embryo transfer

    NARCIS (Netherlands)

    Brogan, P. T.; Henning, H.; Stout, T. A E; de Ruijter-Villani, M.

    2016-01-01

    Colour-flow Doppler sonography has been described as a means of assessing corpus luteum (CL) function rapidly, because area of luteal blood vessels correlates well with circulating progesterone (P4) concentrations [P4] in oestrous cycling mares. The aim of this study was to assess the relationships

  16. Correction of edge-flame propagation speed in a counterflow, annular slot burner

    KAUST Repository

    Tran, Vu Manh

    2015-10-22

    To characterize the propagation modes of flames, flame propagation speed must be accurately calculated. The impact of propagating edge-flames on the flow fields of unburned gases is limited experimentally. Thus, few studies have evaluated true propagation speeds by subtracting the flow velocities of unburned gases from flame displacement speeds. Here, we present a counterflow, annular slot burner that provides an ideal one-dimensional strain rate and lengthwise zero flow velocity that allowed us to study the fundamental behaviors of edge-flames. In addition, our burner has easy optical access for detailed laser diagnostics. Flame displacement speeds were measured using a high-speed camera and related flow fields of unburned gases were visualized by particle image velocimetry. These techniques allowed us to identify significant modifications to the flow fields of unburned gases caused by thermal expansion of the propagating edges, which enabled us to calculate true flame propagation speeds that took into account the flow velocities of unburned gases.

  17. Morphologic features of spontaneous annular tears and disc degeneration in the aging sand rat (Psammomys obesus obesus).

    Science.gov (United States)

    Gruber, H E; Hanley, E N

    2017-08-11

    The sand rat, a member of the gerbil family, is a valuable small animal model in which intervertebral disc degeneration occurs spontaneously as the animal ages. Radiographic features of cervical and lumbar degeneration resemble those in human spines. We conducted a retrospective analysis of spines of 140 animals 3-41 months old focusing specifically on the presence of annular tears that are not visible by radiography and have not been described previously in the sand rat disc. During degeneration of the nucleus pulposus, notochordal cell death occurs and granular material, which stains with Alcian blue for proteoglycans, accumulates. Lamellar architecture also deteriorates and annular tears occur that are morphologically similar to the concentric, radiating and transdiscal annular tears in human discs. These tears contain granular material that provides a "marker" that can be used to distinguish the annular tears from artefactual separations during sectioning. We observed lamellar degeneration and separation in the annulus fibrosus at 4 months with associated tears that contained granular material in the nucleus. Tears that contained granular material and displacement of the degenerating nucleus were common in cervical and lumbar discs of animals older than 9 months; some specimens showed tears at 4 and 5 months. With advanced degeneration, granular globules were displaced dorsally adjacent to and into the spinal cord area and also ventrally into regions where osteophytes formed. We present morphologic data that expand the utility of this rodent model of spontaneous age-related disc degeneration and provide novel information on annular tears and disc degeneration.

  18. Numerical Study of an Annular Gas Turbine Combustor with Dump Diffuser

    Institute of Scientific and Technical Information of China (English)

    J.X.Zhao; Y.B.Lai

    1999-01-01

    A general numerical method is presented for calculating steady three-dimensional and two-phase turbulent reactive flows with a nonstaggered body-fitted coordinate system in an annular gas turbine combustor with the dump diffuser.The modified two-equation model and the EDC turbulent combustion model are used for the gas phase.The liquid phase equations are solved in a Lagrangian frame of reference by PSIC algorithm.The effect of different velocity profiles at the entry of the prediffuser on combustor flow characteristics is calculated.

  19. Assessment of impact of high particulate concentration on peak expiratory flow rate of lungs of sand stone quarry workers.

    Science.gov (United States)

    Singh, Suresh Kumar; Chowdhary, G R; Purohit, Gopal

    2006-12-01

    This study was designed to assess the impact of high particulate concentration on peak expiratory flow rate of lungs of sand stone quarry workers. The workers were engaged in different types of activities such as drilling, loading and dressing. These different working conditions had different concentrations of RSPM, leading to different exposure levels in workers. It was found that exposure duration and exposure concentrations were the main factors responsible for damage to the respiratory tracts of the workers. The particles were deposited at various areas of the respiratory system and reduced the peak flow rate. It was also revealed from the study that most of the workers suffered from silicosis if the exposure duration was more than 20 years.

  20. Trauma-related papular granuloma annular.

    Science.gov (United States)

    Hu, Stephanie W; Kaplan, Jennifer; Patel, Rishi R; Kamino, Hideko

    2013-12-16

    Granuloma annulare (GA) is a benign, granulomatous disease with several clinical manifestations, which include localized, generalized, perforating, subcutaneous, patch, papular, and linear forms. We report a case of papular GA of the dorsal aspects of the hands that arose after repeated, direct trauma to the site of subsequent involvement. Although multiple etiologies for GA have been proposed, which include ultraviolet light, arthropod bites, trauma, tuberculin skin tests, viral infections, and PUVA photochemotherapy, the underlying pathogenesis of the disorder remains unclear. However, owing to the key histopathologic findings of focal collagen and elastic fiber degeneration and mucin deosition in GA, it is not surprising that cutaneous trauma may have played a role in connective tissue injury, subsequent degeneration, and the production of a granulomatous response with increased mucin deposition.

  1. Annular nanoantenna on fibre micro-axicon.

    Science.gov (United States)

    Grosjean, T; Fahys, A; Suarez, M; Charraut, D; Salut, R; Courjon, D

    2008-02-01

    In this paper, we propose to extend the concept of loop antenna to the optical domain. The aim is to develop a new generation of optical nanocollectors that are sensitive to specific electric or magnetic vectorial field components. For validating our approach, a preliminary one-micron-diameter gold nanoring is micromachined on the apex of a cone lens obtained from a tapered optical fibre. It is shown that such a nano-object behaves as a nano-antenna able to detect the longitudinal electric field from a Bessel beam in radial polarization and the longitudinal magnetic component from a Bessel beam in azimuthal polarization. In the latter case, the annular nano-antenna exhibits the properties of an optical inductance.

  2. Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy

    Science.gov (United States)

    Liu, Shaohui; Sun, Lisa L.; Kavanaugh, A. Scott; Langford, Marlyn P.; Liang, Chanping

    2013-01-01

    We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP). Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients. PMID:24348402

  3. Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy

    Directory of Open Access Journals (Sweden)

    Shaohui Liu

    2013-10-01

    Full Text Available We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP. Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients.

  4. Flow Mode Magnetorheological Dampers with an Eccentric Gap

    OpenAIRE

    Choi, Young-Tai; Norman M. Wereley

    2014-01-01

    This paper analyzes flow mode magnetorheological (MR) dampers with an eccentric annular gap (i.e., a nonuniform annular gap). To this end, an MR damper analysis for an eccentric annular gap is constructed based on approximating the eccentric annular gap using a rectangular duct with a variable gap, as well as a Bingham-plastic constitutive model of the MR fluid. Performance of flow mode MR dampers with an eccentric gap was assessed analytically using both field-dependent damping force and dam...

  5. Diagnostics of two-phase flows with high concentration of a solid dispersed phase using fiber-optic sensors

    Science.gov (United States)

    Evseev, A. R.

    2016-10-01

    This paper is focused on the physical modeling of two-phase flows with high concentration of the dispersed phase. The fiber-optical sensors and their calibration procedure were developed for bubble concentration measurements in the fluidized bed apparatus (FB). Distributions of bubble concentration in the 2D and 3D FB apparatuses, which determine the quality of fluidization and local density of filling material, were obtained. The techniques of particle velocity and concentration measurements in the circulating fluidized bed (CFB) was developed using three-fiber sensor (the differential scheme of LDA) operated in backscattering regime. Sensor operation was analyzed and the main systematic measurement errors were determined; the original construction of the sensor was designed. The data on the velocity and concentration profiles of dispersed phase in a large-scale CFB apparatus were obtained for fluidization of particles by air. It was found that with increasing circulation velocity in the CFB apparatus, the particle concentration increases in the near-wall region much higher than in the flow core. The method of particle velocity measurements in a liquid was developed using the laser Doppler fiber anemometer (LDFA-1), operating in the backscattering regime. The signal to noise ratio was obtained for particles of different size and material in test measurements. The rates of consolidated precipitation of cryolite particles in a sedimentation apparatus with the inclined walls were measured.

  6. Characteristics of Electromagnetic Pulse Coupling into Annular Apertures

    Directory of Open Access Journals (Sweden)

    Yan-Peng Sun

    2013-11-01

    Full Text Available Electromagnetic pulse (EMP coupling into the annular apertures can disturb or damage much electronic equipment. To enhance electronic system’s  capability of anti-electromagnetic interference, the finite difference time domain method (FDTD was employed to study the characteristics of electromagnetic pulse coupling into the cavity enclosures with annular apertures. The coupling characteristics of annular apertures with different shapes (rectangle, square and circle were discussed. It shows that, in the case of the same aperture area, the coupling energy of electromagnetic pulse into the circular annular aperture is smaller than that into the rectangular and the square ones. To the rectangular annular aperture, while the polarization direction of the incident electromagnetic pulse is perpendicular to the long side of the rectangular annular aperture, the coupling energy is larger when the aspect ratio of the rectangular annular aperture is larger. The coupling effect of incident pulse with short pulse width is obviously better than the one with longer pulse width. The resonance phenomenon of the coupled waveform occurs in the cavity.

  7. Monitoring sand particle concentration in multiphase flow using acoustic emission technology

    OpenAIRE

    El-Alej, Mohamed Essid

    2014-01-01

    Multiphase flow is the simultaneous flow of two or several phases through a system such as a pipe. This common phenomenon can be found in the petroleum and chemical engineering industrial fields. Transport of sand particles in multiphase production has attracted considerable attention given sand production is a common problem especially to the oil and gas industry. The sand production causes loss of pipe wall thickness which can lead to expensive failures and loss of product...

  8. Biochemical and immunohistochemical comparison of collagen in granuloma annulare and skin sarcoidosis.

    Science.gov (United States)

    Oikarinen, A; Kinnunen, T; Kallioinen, M

    1989-01-01

    Collagen was studied by biochemical and immunohistochemical means in 5 patients with granuloma annulare (GA) and 3 with cutaneous sarcoidosis (SA). The solubility of collagen from the lesional skin in acetic acid was higher than that of collagen from unaffected skin from both patients and control subjects. Collagen concentration in the skin lesions, measured in terms of hydroxyproline content, was reduced in 3 patients with granuloma annulare and one with sarcoidosis, but the ratio of type III/I collagen was unchanged vis-à-vis non-affected skin. The collagen concentration in non-affected skin of both GA and SA-patients was also lower than in controls. The most typical immunohistochemical finding was the association of type III procollagen and fibronectin with granulomas in the lesional skin of both GA and SA cases. The activity of prolyl hydroxylase, a key enzyme in collagen biosynthesis, was markedly increased in the lesional skin, indicating that collagen synthesis in vivo was also increased. Surprisingly, collagen synthesis was not increased in cell culture studies. This could be due to cell selection as observed previously in scleroderma. Another possibility could be that various mediators released in vivo from inflammatory cells activate fibroblasts. However, when cells are subcultivated, this effect is not maintained. In conclusion, marked changes in collagen could be observed in granuloma annulare and skin sarcoidosis, reflecting increased turnover of collagen in vivo.

  9. MICROGRAVITY EXPERIMENTS OF TWO-PHASE FLOW PATTERNS ABOARD MIR SPACE STATION

    Institute of Scientific and Technical Information of China (English)

    赵建福; 解京昌; 林海; 胡文瑞; A.V. Ivanov; A.Yu. Belyaev

    2001-01-01

    A first experimental study on two-phase flow patterns at a long-term,steady microgravity condition was conducted on board the Russian Space Station "MIR" in August 1999. Carbogal and air are used as the liquid and the gas phase,respectively. Bubble, slug, slug-annular transitional, and annular flows are observed.A new region of annular flow with lower liquid superficial velocity is discovered,and the region of the slug-annular transitionalfiow is wider than that observed by experiments on board the parabolic aircraft. The main patterns are bubble, slug annular transitional and annular flows based on the experiments on board MIR space station. Some influences on the two-phase flow patterns in the present experiments are discussed.

  10. The Calculated Ratio of the Gas Flow in a Countercurrent Cyclone Dust Concentrator

    Directory of Open Access Journals (Sweden)

    Vasilevsky Michail

    2016-01-01

    Full Text Available There are numerous studies of the structure of swirling flow in a variety of devices in which the peculiarities of the parameters associated with the twist flow. The values of the local parameters of the twist of the axial direction are experimentally and connect them with a constructive twist parameter, which is built from the idealized repose of the gas flow in vortex distribution and speed at the exit of the swirl. For counter flow chamber is the equation for the input pulse in the radial direction and the twist parameter is provided in the radial direction. It allows us to estimate the maximum radius of the circumferential velocity not only near the outlet, but also near the end surface of the chamber. On a cylindrical surface with a radius of outlet cyclone tangential turbulent friction in the radial direction depends on the product of a circle and radial speeds. Compiled equation changes the flow of angular momentum in the axial zone, depending on the force of friction tangential flow on the surface with the radius of the outlet pipe of the cyclone. This equation allowed assessing the circulation of gas in the axial zone.

  11. HAMLET forms annular oligomers when deposited with phospholipid monolayers.

    Science.gov (United States)

    Baumann, Anne; Gjerde, Anja Underhaug; Ying, Ming; Svanborg, Catharina; Holmsen, Holm; Glomm, Wilhelm R; Martinez, Aurora; Halskau, Oyvind

    2012-04-20

    Recently, the anticancer activity of human α-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine α-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH-as observed by liposome content leakage and circular dichroism experiments-and the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing

    Directory of Open Access Journals (Sweden)

    Kozdera Michal

    2014-03-01

    Full Text Available The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the pressure energy. The sliding bearing is weighted down by axial force, which can be changed during the process. That´s why in front of the particular oil grooves control components adjusting pressure and flow size are located. This paper deals with a project of a hydraulic circuit for regulation of fluid layer in the annular hydrostatic thrust bearing and the testing equipment for measuring its physical properties. It will include the issue of measuring loading capacity and height of the fluid layer in the annular hydrostatic thrust bearing.

  13. Radiation and reflection acoustical fields of an annular phased array

    Institute of Scientific and Technical Information of China (English)

    LAI Puxiang; ZHANG Bixing; WANG Chenghao

    2007-01-01

    The characteristics of the radiation and reflection acoustical fields of an annular phased array are investigated. The effects of the element number, element radius, interelement spacing, centre frequency, focus position, and other parameters on the radiation acoustical field of the annular phased array is theoretically studied. In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experimental measurements are conducted. The radiation acoustical field and its reflection on a liquid-solid interface are theoretically and experimentally studied. The experimental result is in good agreement with the theoretical one.

  14. 几种环形翅片管通道内流体流动与换热特性的对比研究%Comparative Study on Fluid Flow and Heat Transfer Performance in the Channel of Annular Finned Tube

    Institute of Scientific and Technical Information of China (English)

    欧龙姣; 阴继翔; 武广剑; 杨宇伟; 阴勇光

    2016-01-01

    采用 Fluent软件,对基管相同的圆翅片管和5种椭圆翅片管用稳态RNGκ-ε模型进行三维数值模拟,5种椭圆翅片管Afin ,Amin ,De ,Per ,β分别与圆翅片(Cir )有相同的翅片面积、最小截面面积、翅片当量直径、翅片周长和翅化比.通过对不同雷诺数(Re)下流场及翅片表面局部努塞尔数(Nu)的分析比较,得到翅片管通道内流体流动及换热的特征,并提供了圆翅片管和5种椭圆翅片管的综合换热性能Nu/f 的结果.研究表明,圆翅片Cir的Nu大于椭圆翅片Afin ,De ,Per ,β,但小于椭圆翅片Amin .圆翅片的阻力系数f大于椭圆翅片Afin ,Per ,β的f ,且小于椭圆翅片Amin的f.椭圆翅片De 在Re 较小(Re≤8000)时与圆翅片Cir的f的差值较小,在Re较大(Re>8000)时与圆翅片Cir基本相同.椭圆翅片Amin的综合换热效果最好.%The three dimensional numerical simulation of circular finned tube and 5 kinds of elliptical fin tube is performed with the steady state RNGκ-εmodel by the Fluent software.The base pipes of the cir-cular finned tube and five elliptical finned tubes are same.Fluid field and local Nusselt number on fin surface are analyzed and compared for different Reynolds numbers (Re)to obtain fluid flow and heat transfer characteristics in the channel of annular finned tube,and the result of comprehensive heat trans-fer coefficient (Nu/f)on a circular finned tube and 5 elliptical finned tubes is also provided.The results show that the Nu of circular fin is biggest among elliptical fin Afin ,elliptical fin De ,elliptical fin Per and elliptical finβ,but it is smaller than elliptical fin Amin .The flow resistance coefficient of circular fin is biggest among elliptical fin Afin ,elliptical fin Per and elliptical finβ,but it is smaller than elliptical fin Amin .The results of Thermal Resistance is contrary to Nusselts.The difference of flow resistance coeffi-cient between elliptical fin De,and the circular fin is small when the

  15. On the exact analytical solution for the spatial moments of the cross-sectional average concentration in open channel flows

    Science.gov (United States)

    Pannone, Marilena

    2012-08-01

    This paper shows how an exact analytical solution for the transient-state spatial moments of the cross-sectional average tracer concentration in large open channel flows can be derived from the depth-averaged advection-diffusion equation resorting to the method of Green's functions, without any simplifying assumption about the regularity of the actual concentration field, the smallness of the fluctuations, or the large space-time scale of variation of the average concentration gradient (justifying the a priori localization of the problem), which were the basis of the classic Taylor dispersion theory. The results reveal that in agreement with the findings by Aris (1956) and later by others for flows within a conduit, there are an initial centroid displacement and a variance deficit dependent on the specific position and dimension of the initial injection. The second central moment asymptotically tends to the linearly increasing function predictable on the basis of Taylor's classic theory, and the skewness, which is constantly zero for the cross-sectionally uniform injection, in the case of nonuniform initial distributions tends to slowly vanish after having reached a maximum. Thus, the persistent asymmetry exhibited by the field concentration data, as well as the retardations and the accelerations in the peak trajectory, can be justified without making any a priori assumption about the physical mechanism underlying their appearance, like transient storage phenomena, just by rigorously solving the governing equation for the cross-sectional average concentration in the presence of nonuniform, asymmetrically located solute injections.

  16. Effects of detraining after blood flow-restricted low-intensity concentric or eccentric training on muscle size and strength.

    Science.gov (United States)

    Yasuda, Tomohiro; Loenneke, Jeremy P; Thiebaud, Robert S; Abe, Takashi

    2015-01-01

    We investigated the effects of 6 weeks of detraining on muscle size and strength in young men who had previously participated in 6 weeks (3 days/week) of 30 % of concentric one-repetition maximal (1-RM) dumbbell curl training [one arm: concentric blood flow restricted (BFR) exercise (CON-BFR); the other arm: eccentric BFR exercise (ECC-BFR)]. MRI-measured muscle cross-sectional area (CSA) at 10 cm above the elbow joint increased from pre to post (p hypertrophy.

  17. Flow regime, void fraction and interfacial area transport and characteristics of co-current downward two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Lokanathan, Manojkumar [School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088 (United States); Hibiki, Takashi [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017 (United States)

    2016-10-15

    are studied. Moreover, the interfacial area concentration and the bubble coalescence and breakup mechanisms are shown to vary in the axial direction as well as with flow rate, flow area and pressure drop. The liquid velocity field, bubble shape and shear stress are studied for a stationary slug bubble with downward liquid flow. Furthermore, the relationship between the plug and foam flow shape profiles, relative velocity, void fraction and gas slug velocity at an elevated pressure of 0.2 MPa studied by Sekoguchi et al. (1996) are also analyzed, together with the five plug flow sub-regime groups located in the low slip and high slip velocity regions. For the annular flow, the relationship between liquid film thickness, entrainment mechanisms, film velocity and shear stress are studied as well. Alike to plug flow, five sub-regimes in the annular flow are also examined along with the bubble and droplet entrainment mechanisms. The paper also discusses the pressure drop for bubbly, slug, foam, falling film and annular flow regimes, with a particular focus on the most accurate interfacial friction factor correlation for annular flow and its applicability for a wide range of pipe diameters. The flow instability of a system such as static and dynamic instability in the presence of a downcomer, for both single and parallel heated channels are examined too. Finally, the most accurate and versatile drift-flux correlation applicable to all downward flow regimes is highlighted and compared to drift-flux type correlations as it will be a stepping stone to attain a more accurate co-current downward flow transition model. Further experimental effort is essential to achieve a strong foothold in the understanding of co-current downward two-phase flow, as it is vital for nuclear engineering applications.

  18. The concentration gradient flow battery as electricity storage system: Technology potential and energy dissipation

    Science.gov (United States)

    van Egmond, W. J.; Saakes, M.; Porada, S.; Meuwissen, T.; Buisman, C. J. N.; Hamelers, H. V. M.

    2016-09-01

    Unlike traditional fossil fuel plants, the wind and the sun provide power only when the renewable resource is available. To accommodate large scale use of renewable energy sources for efficient power production and utilization, energy storage systems are necessary. Here, we introduce a scalable energy storage system which operates by performing cycles during which energy generated from renewable resource is first used to produce highly concentrated brine and diluate, followed up mixing these two solutions in order to generate power. In this work, we present theoretical results of the attainable energy density as function of salt type and concentration. A linearized Nernst-Planck model is used to describe water, salt and charge transport. We validate our model with experiments over wide range of sodium chloride concentrations (0.025-3 m) and current densities (-49 to +33 A m-2). We find that depending on current density, charge and discharge steps have significantly different thermodynamic efficiency. In addition, we show that at optimal current densities, mechanisms of energy dissipation change with salt concentration. We find the highest thermodynamic efficiency at low concentrate concentrations. When using salt concentrations above 1 m, water and co-ion transport contribute to high energy dissipation due to irreversible mixing.

  19. Lubricating grease shear flow and boundary layers in a concentric cylinder configuration

    NARCIS (Netherlands)

    Li, J.X.; Westerberg, L.G.; Höglund, E.; Lugt, P.M.; Baart, P.

    2014-01-01

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study,

  20. Lubricating grease shear flow and boundary layers in a concentric cylinder configuration

    NARCIS (Netherlands)

    Li, J.X.; Westerberg, L.G.; Höglund, E.; Lugt, Pieter Martin; Baart, P.

    2014-01-01

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study,

  1. A suspension flow model for hydrodynamics and concentration polarisation in crossflow microfiltration

    NARCIS (Netherlands)

    Kromkamp, J.; Bastiaanse, A.; Swarts, J.W.; Brans, G.B.P.W.; Sman, van der R.G.M.; Boom, R.M.

    2005-01-01

    A new computer simulation model is proposed for suspension flow in microfiltration systems. In this model, the diffusion of the suspended microparticles is governed by the mechanism of shear-induced migration. Using an Euler–Euler approach, hydrodynamics and convection–diffusion are simultaneously r

  2. A method for calculating regional cerebral blood flow from emission computed tomography of inert gas concentrations

    DEFF Research Database (Denmark)

    Celsis, P; Goldman, T; Henriksen, L

    1981-01-01

    to avoid loss of information in brain areas with low flow rates. It is based on linearizing and scaling the early isotope distribution picture (recorded from 0 to 2 min) in rCBF units of ml/100 g/min. This is done by calculating the time constant ki for pixels with high count rate using the entire sequence...

  3. Multiple Scattering: Dispersion, Temperature Dependence, and Annular Pistons

    CERN Document Server

    Milton, Kimball A; Parashar, Prachi; Cavero-Pelaez, Ines; Brevik, Iver; Ellingsen, Simen A

    2010-01-01

    We review various applications of the multiple scattering approach to the calculation of Casimir forces between separate bodies, including dispersion, wedge geometries, annular pistons, and temperature dependence. Exact results are obtained in many cases.

  4. Phased annular array transducers for ultrasonic guided wave applications

    Science.gov (United States)

    Yan, Fei; Borigo, Cody; Liang, Yue; Koduru, Jaya P.; Rose, Joseph L.

    2011-04-01

    Mode and frequency control always plays an important role in ultrasonic guided wave applications. In this paper, theoretical understanding of guided wave excitations of axisymmetric sources on plate structures is established. It is shown that a wave number spectrum can be used to investigate the guided wave excitations of an axisymmetric source. The wave number spectrum is calculated from a Hankel transform of the axial source loading profile. On the basis of the theoretical understanding, phased annular array transducers are developed as a powerful tool for guided wave mode and frequency control. By applying appropriate time delays to phase the multiple elements of an annular array transducer, guided wave mode and frequency tuning can be achieved fully electronically. The phased annular array transducers have been successfully used for various applications. Example applications presented in this paper include phased annular arrays for guided wave beamforming and a novel ultrasonic vibration modal analysis technique for damage detection.

  5. Virtual cathode microwave generator having annular anode slit

    Science.gov (United States)

    Kwan, Thomas J. T.; Snell, Charles M.

    1988-01-01

    A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit therethrough effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators.

  6. Polyharmonic functions of infinite order on annular regions

    OpenAIRE

    Kounchev, Ognyan; Render, Hermann

    2013-01-01

    Polyharmonic functions $f$ of infinite order and type $\\tau$ on annular regions are systematically studied. The first main result states that the Fourier-Laplace coefficients $f_{k,l}(r)$ of a polyharmonic function $f$ of infinite order and type $0$ can be extended to analytic functions on the complex plane cut along the negative semiaxis. The second main result gives a constructive procedure via Fourier-Laplace series for the analytic extension of a polyharmonic function on annular ...

  7. Experiments on soliton motion in annular Josephson junctions

    DEFF Research Database (Denmark)

    Davidson, A.; Dueholm, B.; Pedersen, Niels Falsig

    1986-01-01

    We report here the results of an extensive experimental investigation of soliton dynamics in Josephson junctions of different annular geometries. The annular geometry is unique in that it allows for the study of undisturbed soliton motion as well as soliton–antisoliton collisons, since there are ...... for a single trapped soliton, and evidence linking the stability of the soliton to surface damping. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  8. Experimental study of horizontal annular channels under non-developed conditions

    Energy Technology Data Exchange (ETDEWEB)

    Delgadino, G. [Rensselaer Polytechnic Institute, Troy, NY (United States); Balino, J.; Carrica, P. [Centro Atomico Bariloche e Instituto Balseriro (Argentina)

    1995-09-01

    In this work an experimental study of the two-phase air-water flow in a horizontal annular channel under non-developed conditions is presented. A conductive local probe was placed at the end of the channel to measure the local phase indication function under a wide range of gas and water flow rates. The signal was processed to obtain the void fraction and statistical distributions of liquid and gas residence times. From these data the topology of the flow could be inferred. A laser intermittence detector was also located close to the channel exit, in order to measure statistical parameters for intermittent flows by means of a two-probe method.

  9. Crossover of the thermal escape problem in annular spatially distributed systems.

    Science.gov (United States)

    Fedorov, Kirill G; Pankratov, Andrey L

    2009-12-31

    The computer simulations of fluctuational dynamics of an annular system governed by the sine-Gordon model with a white noise source are performed. It is demonstrated that the mean escape time (MET) of a phase string for an annular structure can be much larger than for a linear one and has a strongly pronounced maximum as a function of system's length. The location of the MET maximum roughly equals the size of the kink-antikink pair, which leads to evidence of a spatial crossover between two dynamical regimes: when the phase string escapes over the potential barrier as a whole and when the creation of kink-antikink pairs is the main mechanism of the escape process. For large lengths and in the limit of small noise intensity gamma, for both MET and inverse concentration of kinks, we observe the same dependence versus the kink energy E(k): approximately exp(2E(k)/gamma) for the annular structure and approximately exp(E(k)/gamma) for the linear one.

  10. Solution Concentration and Flow Rate of Fe3+-modified Porphyrin (Red Blood Model) on Giant Magnetoresistance (GMR) Sensor Efficiency

    Science.gov (United States)

    Aminudin, A.; Tjahyono, D. H.; Suprijadi; Djamal, M.; Zaen, R.; Nandiyanto, A. B. D.

    2017-03-01

    Red blood has been of great interest for scientists since it relates to human’ and living creature’s life sustainability. One of the important compounds in red blood is porphyrin. Here, the purpose of this study was to develop a method for detecting porphyrin concentration using the assistance of giant magnetoresistance. In short of the method, we added Fe3+ solution to the porphyrin, and the mixed solution was introduced to the magnetic field. Next, the magnetized solution was introduced to the magnetic sensor to indicate the existence of porphyrin in the solution. To confirm the effectiveness of our method in detecting porphyrin, we varied the flow rate and concentration of Fe3+-modified porphyrin solution. The result showed that the more concentration and the slower flow rate affected the higher sensitivity gained. Since this developed method is simple but effective for detecting porphyrin concentration, we believe that further development of this method will be benefit for many applications, specifically relating to the medical uses.

  11. Nitrate Loads and Concentrations in Surface-Water Base Flow and Shallow Groundwater for Selected Basins in the United States, Water Years 1990-2006

    Science.gov (United States)

    Spahr, Norman E.; Dubrovsky, Neil M.; Gronberg, JoAnn M.; Franke, O. Lehn; Wolock, David M.

    2010-01-01

    nutrient management practices designed to reduce nutrient transport to streams by runoff. Conversely, sites with potential for shallow or deep groundwater contribution (some combination of permeable soils or permeable bedrock) had significantly greater contributions of nitrate from base flow. Effective nutrient management strategies would consider groundwater nitrate contributions in these areas. Mean annual base-flow nitrate concentrations were compared to shallow-groundwater nitrate concentrations for 27 sites. Concentrations in groundwater tended to be greater than base-flow concentrations for this group of sites. Sites where groundwater concentrations were much greater than base-flow concentrations were found in areas of high infiltration and oxic groundwater conditions. The lack of correspondingly high concentrations in the base flow of the paired surface-water sites may have multiple causes. In some settings, there has not been sufficient time for enough high-nitrate shallow groundwater to migrate to the nearby stream. In these cases, the stream nitrate concentrations lag behind those in the shallow groundwater, and concentrations may increase in the future as more high-nitrate groundwater reaches the stream. Alternatively, some of these sites may have processes that rapidly remove nitrate as water moves from the aquifer into the stream channel. Partitioning streamflow and nitrate load between the quick-flow and base-flow portions of the hydrograph coupled with relative scales of soil permeability can infer the importance of surface water compared to groundwater nitrate sources. Study of the relation of nitrate concentrations to base-flow index and the comparison of groundwater nitrate concentrations to stream nitrate concentrations during times when base-flow index is high can provide evidence of potential nitrate transport mechanisms. Accounting for the surface-water and groundwater contributions of nitrate is crucial to effective management and remediat

  12. New mitral annular force transducer optimized to distinguish annular segments and multi-plane forces.

    Science.gov (United States)

    Skov, Søren Nielsen; Røpcke, Diana Mathilde; Ilkjær, Christine; Rasmussen, Jonas; Tjørnild, Marcell Juan; Jimenez, Jorge H; Yoganathan, Ajit P; Nygaard, Hans; Nielsen, Sten Lyager; Jensen, Morten Olgaard

    2016-03-21

    Limited knowledge exists about the forces acting on mitral valve annuloplasty repair devices. The aim of this study was to develop a new mitral annular force transducer to measure the forces acting on clinically used mitral valve annuloplasty devices. The design of an X-shaped transducer in the present study was optimized for simultaneous in- and out-of-plane force measurements. Each arm was mounted with strain gauges on four circumferential elements to measure out-of-plane forces, and the central parts of the X-arms were mounted with two strain gauges to measure in-plane forces. A dedicated calibration setup was developed to calibrate isolated forces with tension and compression for in- and out-of-plane measurements. With this setup, it was possible with linear equations to isolate and distinguish measured forces between the two planes and minimize transducer arm crosstalk. An in-vitro test was performed to verify the crosstalk elimination method and the assumptions behind it. The force transducer was implanted and evaluated in an 80kg porcine in-vivo model. Following crosstalk elimination, in-plane systolic force accumulation was found to be in average 4.0±0.1N and the out-of-plane annular segments experienced an average force of 1.4±0.4N. Directions of the systolic out-of-plane forces indicated movements towards a saddle shaped annulus, and the transducer was able to measure independent directional forces in individual annular segments. Further measurements with the new transducer coupled with clinical annuloplasty rings will provide a detailed insight into the biomechanical dynamics of these devices.

  13. Dissipative particle dynamics simulation of flow generated by two rotating concentric cylinders: boundary conditions.

    Science.gov (United States)

    Haber, S; Filipovic, N; Kojic, M; Tsuda, A

    2006-10-01

    The dissipative particle dynamics (DPD) method was used to simulate the flow in a system comprised of a fluid occupying the space between two cylinders rotating with equal angular velocities. The fluid, initially at rest, ultimately reaches a steady, linear velocity distribution (a rigid-body rotation). Since the induced flow field is solely associated with the no-slip boundary condition at the walls, we employed this system as a benchmark to examine the effect of bounce-back reflections, specular reflections, and Pivkin-Karniadakis no-slip boundary conditions, upon the steady-state velocity, density, and temperature distributions. An additional advantage of the foregoing system is that the fluid occupies inherently a finite bounded domain so that the results are affected by the prescribed no-slip boundary conditions only. Past benchmark systems such as Couette flow between two infinite parallel plates or Poiseuille flow in an infinitely long cylinder must employ artificial periodic boundary conditions at arbitrary upstream and downstream locations, a possible source of spurious effects. In addition, the effect of the foregoing boundary conditions on the time evolution of the simulated velocity profile was compared with that of the known, time-dependent analytical solution. It was shown that bounce-back reflection yields the best results for the velocity distributions with small fluctuations in density and temperature at the inner fluid domain and larger deviations near the walls. For the unsteady solutions a good fit is obtained if the DPD friction coefficient is proportional to the kinematic viscosity. Based on dimensional analysis and the numerical results a universal correlation is suggested between the friction coefficient and the kinematic viscosity.

  14. Accounting for Surface Concentrations Using a VOF Front Tracking Method in Multiphase Flow

    OpenAIRE

    Martin, David Warren

    2015-01-01

    In this dissertation, we present a numerical method for trackingsurfactants on an interface in multiphase flow, along withapplications of the method to two physical problems. We alsopresent an extension of our method to track charged droplets. Ourmethod combines a traditional volume of fluid (VOF) method withmarker tracking. After describing this method in detail, wepresent a series of tests we used to validate our method. Theapplications we consider are the coalescence of surfactant-ladendro...

  15. Effects of blood flow restricted low-intensity concentric or eccentric training on muscle size and strength.

    Science.gov (United States)

    Yasuda, Tomohiro; Loenneke, Jeremy P; Thiebaud, Robert S; Abe, Takashi

    2012-01-01

    We investigated the acute and chronic effects of low-intensity concentric or eccentric resistance training with blood flow restriction (BFR) on muscle size and strength. Ten young men performed 30% of concentric one repetition maximal dumbbell curl exercise (four sets, total 75 reps) 3 days/week for 6 weeks. One arm was randomly chosen for concentric BFR (CON-BFR) exercise only and the other arm performed eccentric BFR (ECC-BFR) exercise only at the same exercise load. During the exercise session, iEMG for biceps brachii muscles increased progressively during CON-BFR, which was greater (pexercise, muscle thickness (MTH) of the elbow flexors acutely increased (phypertrophy with BFR resistance training.

  16. A comparative study of friction factor correlations for high concentrate slurry flow in smooth pipes

    Directory of Open Access Journals (Sweden)

    Assefa K. M.

    2015-03-01

    Full Text Available A number of correlations for friction factor determinations in smooth pipes have been proposed in the past decades. The accuracy and applicability of these friction factor formulas should be examined. Based on this notion the paper is designed to provide a comparative study of friction factor correlations in smooth pipes for all flow regimes of Bingham fluids. Nine models were chosen. The comparisons of the selected equations with the existing experimental results, which are available in the literature, were expressed through MARE, MRE+, MRE-, RMSE, Ѳ, and S. The statistical comparisons were also carried out using MSC and AIC. The analyses show that the Wilson-Thomas (1985 and Morrison (2013 models are best fit models to the experimental data for the Reynolds number up to 40000. Within this range, both models can be used alternately. But beyond this Re value the discrepancy of the Wilson-Thomas model is higher than the Morrison model. In view of the fact that the Morrison model requires fewer calculations and parameters as well as a single equation is used to compute the friction factor for all flow regimes, it is the authors’ advice to use this model for friction factor estimation for the flow of Bingham fluids in smooth pipes as an alternative to the Moody chart and other implicit formulae.

  17. Coupling Discrete and Continuum Mechanics in Low Concentration, Particle-Laden Flows

    Science.gov (United States)

    Boyle, Paul; Houchens, Brent; Kim, Albert

    2008-11-01

    The study of particle-laden flow plays a critical role in pressure-driven membrane filtration such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Hydrodynamic and inter-particle interactions, coupled to the ambient crossflow field, are well documented in literature. Transport of particles is originated due to Brownian and shear-induced diffusion, and convection due to the axial crossflow and transverse permeate flow. These effects are modeled using Hydrodynamic Force Bias Monte Carlo (HFBMC) simulations to predict the deposition of the particles on the membrane surface. In addition, the particles in the simulation are also subject to electrostatic double layer repulsion and van der Waals attraction both between particles and between the particles and membrane surfaces. In conjunction with the hydrodynamics, the change in particle potential determines the transition probability that a proposed, random move of a particle will be accepted. In the current study, these discrete particle effects at the microscopic level are coupled to the continuum flow via an apparent local viscosity, yielding a quasi-steady-state velocity profile. This velocity profile is dynamically updated in order to refine the hydrodynamic interactions. The resulting simulation predicts the formation of a cake layer of deposited interacting particles on the membrane surface.

  18. Correlation between air flow rate and pollutant concentrations during two-stage oak log combustion in a 25 KW residential boiler

    Directory of Open Access Journals (Sweden)

    Juszczak Marek

    2016-09-01

    Full Text Available It can be expected that there is a considerable correlation between combustion air flow rate and the concentrations of carbon monoxide, hydrocarbons and nitrogen oxide in the flue gas. The influence of temperature and oxygen concentration in the combustion zone on the concentrations of carbon monoxide, hydrocarbons and nitrogen oxide in the flue gas, for high and low combustion air flow, was analysed. Oxygen concentration for which the concentration of carbon monoxide is the lowest was determined, as well as the mutual relation between carbon monoxide and nitrogen oxide concentration.

  19. Sonographic evaluation of digital annular pulley tears

    Energy Technology Data Exchange (ETDEWEB)

    Martinoli, C.; Derchi, L.E. [Istituto di Radiologia, Universita di Genova, Genoa (Italy); Bianchi, S.; Garcia, J.F. [Dept. de Radiologie, Hopital Cantonal Universitaire de Geneve (Switzerland); Nebiolo, M. [Reparto Pronto Soccorso Medico, Pietra Ligure (Italy)

    2000-07-01

    Objective. To evaluate the sonographic (US) appearance of digital annular pulley (DAP) tears in high-level rock climbers. Design and patients. We performed a retrospective analysis of the US examinations of 16 high-level rock climbers with clinical signs of DAP lesions. MRI and surgical evaluation were performed in five and three patients respectively. The normal US and MRI appearances of DAP were evaluated in 40 and three normal fingers respectively. Results. Nine of 16 patients presented a DAP tear. In eight subjects (seven with complete tears involving the fourth finger and one the fifth finger), US diagnosis was based on the indirect sign of volar bowstringing of the flexor tendons. Injured pulleys were not appreciated by US. Tears concerned the A2 and A3 in six patients and the A3 and A4 in two patients. A2 pulley thickening and hypoechogenicity compatible with a partial tear was demonstrated in one patient. MRI and surgical data correlated well with the US findings. Four patients had tenosynovitis of the flexor tendons but no evidence of pulley disruption. US examinations of three patients were normal. In the healthy subjects US demonstrated DAP in 16 of 40 digits. Conclusion. US can diagnose DAP tears and correlates with the MRI and surgical data. Because of its low cost and non-invasiveness we suggest US as the first imaging modality in the evaluation of injuries of the digital pulley. (orig.)

  20. Vibration of an eccentrically clamped annular plate

    Science.gov (United States)

    Tseng, J.-G.; Wickert, J. A.

    1994-04-01

    Small amplitude vibration of an eccentric annular plate, which is free along its outer edge and clamped along the interior, is investigated through experimental and analytical methods. A disk with this geometry, or a stacked array in which the clamping and symmetry axes of each disk are nominally coincident, is common in data storage and brake systems applications. In the present case, the geometric imperfections on the boundary can have important implications for the disk's dynamic response. Changes that occur in the natural frequency spectrum, the mode shapes, and the free response under eccentric mounting are studied through laboratory measurements and an approximate discrete model of the plate. The natural frequencies and modes are found through global discretization of the Kamke quotient for a classical thin plate. For the axisymmetric geometry, the natural frequencies of the sine and cosine vibration modes for a specified number of nodal diameters are repeated. With increasing eccentricity, on the other hand, each pair of repeated frequencies splits at a rate that depends on the number of nodal diameters. Over a range of clamping and eccentricity ratios, the model's predictions are compared to the measured results.