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Sample records for cstr flow pattern

  1. Relationship between first-order decay coefficients in ponds, for plug flow, CSTR and dispersed flow regimes.

    Science.gov (United States)

    von, Sperling M

    2002-01-01

    Adequate consideration of the hydraulic regime of a pond is essential in the analysis of BOD and coliform removal, and considerable divergence exists in the literature when reporting removal coefficients. This paper aims at integrating the existing approaches, by quantifying the relationship between the first-order removal coefficients K from the three main hydraulic regimes (CSTR, plug flow and dispersed flow) adopted in the design and performance evaluation of ponds. Based on theoretical considerations and statistical regression analyses, the relationship between the K values is investigated, quantified and modelled. Two tables are presented and two equations are proposed, which allow conversion of K values obtained for dispersed flow to (a) K for CSTR and (b) K for plug flow, based on the hydraulic detention time t and the dispersion number d. These coefficients, when applied in the CSTR or plug-flow equations, will give approximately the same prediction of the effluent concentration as that obtained when using the dispersed-flow model with its proper coefficient. With this approach designers can apply, and researchers can report, K values for the two idealised flow patterns (CSTR and plug flow).

  2. Multiple ranges of flow rate with bistability and limit cycles for Schlögl's mechanism in a CSTR

    Science.gov (United States)

    Escher, Claus; Ross, John

    1983-10-01

    Continuous flow stirred tank reactor (CSTR) conditions are imposed upon Schlögl's trimolecular reaction mechanism A+2X ⇄ 3X and X ⇄ B. A nonzero constant flow rate (=inverse residence time) rather than constant concentrations of A,B forces the system far away from equilibrium. This change in constraints leads to some surprisingly complex features; first the system has bistability for separate ranges of flow rates, under constraints of all other parameters being fixed including the concentration of the chemical species in the input. This phenomena occurs even if the input contains A alone. Secondly, there occur limit cycle oscillations, but in that case the input has to include B or X as well as A.

  3. Nonlinear dynamical behavior of the limited Explodator in a CSTR under square wave perturbation of the flow rate

    Science.gov (United States)

    Wu, Xiaomao; Schelly, Z. A.; Vastano, John A.

    1994-07-01

    Results of studies of the limited Explodator model in a continuous-flow stirred tank reactor (CSTR) under square wave perturbation of the flow rate are reported. The perturbation is applied in such a way that the system is alternately attracted to two different periodic attractors in the parameter region close the Hopf bifurcation point. The system is shown to display a variety of entrainment bands, birhythmicity, quasiperiodicity, resonance-like phenomenon, period doubling and intermittency routes to chaos, and a complicated window structure of the chaotic region. In addition, a novel phenomenon, “intermittent alternative laminar oscillations”, was observed in a chaotic regime sandwiched between two entrainment bands. Transient chaos occurs in one of the entrainment bands, which intimates chaos in the adjacent regime. Positive Lyapunov exponents were found to be associated with the chaotic behavior. The folding and stretching property of the chaotic attractors was analyzed through stroboscopic representations. The deterministic nature of the chaotic behavior was confirmed by the quadratic-like curve formed in the one-dimensional map.

  4. Serial CSTR digester configuration for improving biogas production from manure

    DEFF Research Database (Denmark)

    Boe, Kanokwan; Angelidaki, Irini

    2009-01-01

    A new configuration of manure digesters for improving biogas production has been investigated in laboratory scale. A single thermophilic continuous-flow stirred tank reactor (CSTR) operated with a hydraulic retention time (HRT) of 15 days was compared to a serial CSTR configuration with volume...... distribution ratio of 80/20 and 90/10, and total HRT of 15 days. The results showed that the serial CSTR could obtain 11% higher biogas yield compared to the single CSTR. The increased biogas yield in the serial CSTR was mainly from the second reactor, which accounted for 16% and 12% of total biogas yield...... in the 90/10 and 80/20 configuration, respectively. VFA concentration in the serial CSTR was high in the first reactor but very low in the second reactor. The results from organic pulse load test showed that the second reactor in serial CSTR helped utilizing VFA produced from overloading in the first...

  5. Serial CSTR digester configuration for improving biogas production from manure.

    Science.gov (United States)

    Boe, Kanokwan; Angelidaki, Irini

    2009-01-01

    A new configuration of manure digesters for improving biogas production has been investigated in laboratory scale. A single thermophilic continuous-flow stirred tank reactor (CSTR) operated with a hydraulic retention time (HRT) of 15 days was compared to a serial CSTR configuration with volume distribution ratio of 80/20 and 90/10, and total HRT of 15 days. The results showed that the serial CSTR could obtain 11% higher biogas yield compared to the single CSTR. The increased biogas yield in the serial CSTR was mainly from the second reactor, which accounted for 16% and 12% of total biogas yield in the 90/10 and 80/20 configuration, respectively. VFA concentration in the serial CSTR was high in the first reactor but very low in the second reactor. The results from organic pulse load test showed that the second reactor in serial CSTR helped utilizing VFA produced from overloading in the first reactor, which improved the effluent quality and conversion efficiency of the serial CSTR.

  6. Stochastic simulation of material flow in the CSTR reactor system%CSTR反应系统中物料流动的随机模拟

    Institute of Scientific and Technical Information of China (English)

    颜清; 彭小平

    2012-01-01

    Micelle flowing inside the material is ideally mixed CSTR single or multiple reaction system, and the status of the outflow of material micelle reaction system has the statistical characteristics of the flowing of tracer analog materials micelles in the reaction system,which is commonly used method. Tracers the number of micelles per unit time in the number of element is in line with the law of large numbers, a single tracer parcels in out of the reaction system to a random probability statistics. By using Excel tables, functions, features and VBA hybrid programming, they overcome the shortcomings of the other programming software to deal with the simulation data that is less satisfactory, and are very close to the simulation with the theoretical flow conditions of the material in the CSTR reactor system, in order to explore and reveal each class reactor flow characteristics and provides an effective solution.%对于器内物料微团的流动处于理想混合状态的单个或多个CSTR组成的反应系统,物料微团流出反应系统的状况具有统计特征,用示踪剂模拟物料微团在反应系统中流动特性是常用的方法.由于示踪剂微团数目和单位时间中的时间微元数目均符合大数定理,单个示踪剂微团的流出反应系统成为随机概率的统计问题.利用Excel表格、函数功能及VBA混合编程,克服了其他编程软件对处理模拟数据不太尽如人意的缺点,与理论推导十分接近的模拟了CSTR反应系统内物料的流动状况,为探索和揭示各类反应器流动特性提供了一种有效解决途径.

  7. Study of mixing behavior of cstr using CFD

    Directory of Open Access Journals (Sweden)

    D. Rajavathsavai

    2014-03-01

    Full Text Available The continuous stirred tank reactor (CSTR is a widely used equipment in chemical related industries. The flow behaviour of fluid inside the reactor may either change from dispersion to ideal or ideal to dispersion mixing state. It is studied using the computational fluid dynamics (CFD simulation software ANSYS Fluent. The mixing behaviour is predicted in terms of age distribution function, I (θ. For the CSTR without impeller and baffles, I (θ is found by the tracer injection method. It is measured and predicted by the impeller swept volume method for the CSTR in the presence of impeller and baffles. The predicted results are found to be in good agreement with the literature experimental data. Effect of rpm of the impeller, Reynolds number and viscosity of the process fluid on the mixing characteristics has been investigated.

  8. Effect of wall growth on the kinetic modeling of nitrite oxidation in a CSTR.

    Science.gov (United States)

    Dokianakis, Spiros N; Kornaros, Michael; Lyberatos, Gerasimos

    2006-03-05

    A simple kinetic model was developed for describing nitrite oxidation by autotrophic aerobic nitrifiers in a continuous stirred tank reactor (CSTR), in which mixed (suspended and attached) growth conditions prevail. The CSTR system was operated under conditions of constant nitrite feed concentration and varying volumetric flow rates. Experimental data from steady-state conditions in the CSTR system and from batch experiments were used for the determination of the model's kinetic parameters. Model predictions were verified against experimental data obtained under transient operating conditions, when volumetric flow rate and nitrite feed concentration disturbances were imposed on the CSTR. The presented kinetic modeling procedure is quite simple and general and therefore can also be applied to other mixed growth biological systems.

  9. Test Results for CSTR Test 4

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.D.

    2001-05-31

    One of the 3 technologies currently being developed for the Savannah River Salt Waste Processing Program is the Small-Tank Tetraphenylborate Process (STTP). This process uses sodium tetraphenylborate to precipitate and remove radioactive Cs from the waste and monosodium titanate to sorb and remove radioactive Sr and actinides. ORNL is demonstrating this process at the 1:4000 scale using a 20-liter continuous-flow stirred tank reactor (CSTR) system. The primary goal of Test 4 was to verify that the STTP process could achieve and maintain the necessary Cs decontamination while TPB was actively decomposing. Even with TPB being decomposed by the off-normal conditions of this test, the decontaimination factor for {sup 137}Cs obtained for the filtrate from the Slurry Concentrating Tank ranged from 47,000 to 646,000, exceeding the WAC standard.

  10. Test Results for CSTR Test 3

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.D.

    2000-10-12

    The goal of the Savannah River Salt Waste Processing Program (SPP) is to evaluate and select the most effective technology for the treatment of the high-level waste salt solutions currently being stored in underground storage tanks at the U.S. Department of Energy Savannah River Site (SRS) in Aiken, South Carolina. One of the three technologies currently being developed for this application is the Small-Tank Tetraphenylborate Process (STTP). This process uses sodium tetraphenylborate (NaTPB) to precipitate and remove radioactive cesium from the waste and monosodium titanate (MST) to sorb and remove radioactive strontium and actinides. Oak Ridge National Laboratory is demonstrating this process at the 1:4000 scale using a 20-L capacity continuous-flow stirred-tank reactor (CSTR) system. Since March 1999, three operating campaigns of the 20-L CSTR have been conducted. The ultimate goal is to verify that this process, under certain extremes of operating conditions, can meet the minimum treatment criteria necessary for processing and disposal at the Savannah River Saltstone Facility. The waste acceptance criteria (WAC) for {sup 137}Cs, {sup 90}Sr, and total actinides are <40 nCi/g, <40 nCi/g, and <18 nCi/g, respectively. However, to allow for changes in process conditions, SPP is seeking a level of treatment that is about 50% of the WAC. The bounding separation goals for {sup 137}Cs and {sup 90}Sr are to obtain decontamination factors (DFs) of 40,000 (99.998% removal) and 26 (96.15% removal), respectively. The DF is defined as the concentration of contaminant in the waste divided by the concentration of contaminant in the effluent stream.

  11. Flow-distributed oscillations: Stationary chemical waves in a reacting flow

    Science.gov (United States)

    Kærn, Mads; Menzinger, Michael

    1999-10-01

    A recent prediction of stationary waves in open, reacting flows is experimentally verified. We show that stationary waves are generated by a mechanism whereby the flow carries a time-oscillating subelement, behaving like a batch reactor, through space while a fixed boundary condition at the inflow locks the phase of the oscillation. This mechanism can generate stationary patterns when all diffusion coefficients are equal. The experimental system is the ferroin-catalyzed Belousov-Zhabotinsky reaction in a tubular reactor, fed by the outflow of a continuous flow stirred tank reactor (CSTR). Parameter conditions are such that the concentrations are constant in the CSTR while they oscillate in the flow tube.

  12. Flow pattern in reverse-flow centrifugal separators

    NARCIS (Netherlands)

    Peng, W; Hoffmann, AC; Boot, PJAJ; Udding, A; Dries, HWA; Ekker, A; Kater, J

    2002-01-01

    Experimental flow patterns, determined by Laser Doppler Anemometry (LDA) for two types of reverse-flow centrifugal separators, are presented. The flow patterns in (a) a conventional cylinder-on-cone cyclone with tangential inlet and (b) a swirl tube with vane-generated swirl and a cylindrical body a

  13. Climatology of local flow patterns around Basel

    Energy Technology Data Exchange (ETDEWEB)

    Weber, R.O. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Recently a method has been developed to classify local-scale flow patterns from the wind measurements at a dense network of stations. It was found that in the MISTRAL area around Basel a dozen characteristic flow patterns occur. However, as the dense network of stations ran only during one year, no reliable climatology can be inferred from these data, especially the annual cycle of the flow patterns is not well determined from a single year of observations. As there exist several routinely operated stations in and near the MISTRAL area, a method was searched to identify the local flow patterns from the observations at the few routine stations. A linear discriminant analysis turned out to be the best method. Based of data from 11 stations which were simultaneously operated during 1990-1995 a six-year climatology of the flow patterns could be obtained. (author) 1 fig., 1 tab., 3 refs.

  14. Complex dynamic behavior in the bromate-oxalic acid-acetone-Mn(II) oscillating reaction in a continuous stirred tank reactor (CSTR)

    Science.gov (United States)

    Silva, Lucyane C.; Faria, Roberto B.

    2007-05-01

    The oscillating reaction bromate-oxalic acid-acetone-Mn(II)-sulfuric acid was observed for the first time in a CSTR at 20 °C. Depending on the bromate concentrations and flow rate, the system showed large amplitude oscillations, two kinds of mixed mode oscillations, quasiperiodicity and bursts of large amplitude oscillations, all mapped in a phase diagram. More complex behavior was favored at low bromate concentrations. The system without acetone was discovered to oscillate too, but the more complex patterns were not seen, indicating that acetone is implied in their formation.

  15. Arterial secondary blood flow patterns visualized with vector flow ultrasound

    DEFF Research Database (Denmark)

    Pedersen, Mads Møller; Pihl, Michael Johannes; Hansen, Jens Munk

    2011-01-01

    This study presents the first quantification and visualisation of secondary flow patterns with vector flow ultrasound. The first commercial implementation of the vector flow method Transverse Oscillation was used to obtain in-vivo, 2D vector fields in real-time. The hypothesis of this study...

  16. Unraveling flow patterns through nonlinear manifold learning.

    Science.gov (United States)

    Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

    2014-01-01

    From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap) to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features.

  17. Unraveling flow patterns through nonlinear manifold learning.

    Directory of Open Access Journals (Sweden)

    Flavia Tauro

    Full Text Available From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features.

  18. Precipitation patterns during channel flow

    Science.gov (United States)

    Jamtveit, B.; Hawkins, C.; Benning, L. G.; Meier, D.; Hammer, O.; Angheluta, L.

    2013-12-01

    Mineral precipitation during channelized fluid flow is widespread in a wide variety of geological systems. It is also a common and costly phenomenon in many industrial processes that involve fluid flow in pipelines. It is often referred to as scale formation and encountered in a large number of industries, including paper production, chemical manufacturing, cement operations, food processing, as well as non-renewable (i.e. oil and gas) and renewable (i.e. geothermal) energy production. We have studied the incipient stages of growth of amorphous silica on steel plates emplaced into the central areas of the ca. 1 meter in diameter sized pipelines used at the hydrothermal power plant at Hellisheidi, Iceland (with a capacity of ca 300 MW electricity and 100 MW hot water). Silica precipitation takes place over a period of ca. 2 months at approximately 120°C and a flow rate around 1 m/s. The growth produces asymmetric ca. 1mm high dendritic structures ';leaning' towards the incoming fluid flow. A novel phase-field model combined with the lattice Boltzmann method is introduced to study how the growth morphologies vary under different hydrodynamic conditions, including non-laminar systems with turbulent mixing. The model accurately predicts the observed morphologies and is directly relevant for understanding the more general problem of precipitation influenced by turbulent mixing during flow in channels with rough walls and even for porous flow. Reference: Hawkins, C., Angheluta, L., Hammer, Ø., and Jamtveit, B., Precipitation dendrites in channel flow. Europhysics Letters, 102, 54001

  19. Analyzing highway flow patterns using cluster analysis

    NARCIS (Netherlands)

    Weijermars, Wendy; van Berkum, Eric C.; Pfliegl, R.

    2005-01-01

    Historical traffic patterns can be used for the prediction of traffic flows, as input for macroscopic traffic models, for the imputation of missing or erroneous data and as a basis for traffic management scenarios. This paper investigates the determination of historical traffic patterns by means of

  20. Effect of Operating Conditions on CSTR performance: an Experimental Study

    Directory of Open Access Journals (Sweden)

    Mohd Danish

    2015-02-01

    Full Text Available In this work, Saponification reaction of ethyl acetate by sodium hydroxide is studied experimentally in a continuous stirred tank reactor at 1 atmospheric pressure. The aim of this study is to investigate the influence of operating conditions on the conversion and specific rate constant. The parameters considered for analysis are temperature, feed flow rate, residence time, volume of reactor and stirrer rate. The steady state conversion of 0.45 achieved after a period of 30 minutes. Conversion decreases with increase of reactant flow rate due to decrease of residence time. The stirrer rate has a positive effect on the conversion and rate constant. Specific rate constant and conversion increase with temperature within the studied temperature range. Within the range of reactor volume selected for analysis, conversion increases with increase in reactor volume. The results obtained in this study may be helpful in maximizing the conversion of ethyl acetate saponification reaction at industrial scale in a CSTR.

  1. FLOW PATTERNS AND DAMAGE OF DIKE OVERTOPPING

    Institute of Scientific and Technical Information of China (English)

    Chaiyuth CHINNARASRI; Tawatchai TINGSANCHALI; Sutat WEESAKUL; Somchai WONGWISES

    2003-01-01

    Damage of a dike may result in severe damage and suffering. To reduce downstream damage and loss of life, it is important to study the process of breaching of the damaged dike. It is not possible to understand the damage process without a clear understanding of the flow patterns encountered. In the present study, data obtained from nine experimental runs are analyzed. The flow patterns and progressive damage of dike overtopping are investigated. Two types of phenomena at the dike surface:erosion; and erosion and sliding, are observed during the overtopping event. Four stages of dike damage can be distinguished. The degradation rate of the dike crest is found to be dependent on the downstream slope of the dike. The degradation rate is higher when the downstream slope is steeper.

  2. Characteristic flow patterns generated by macrozoobenthic structures

    Science.gov (United States)

    Friedrichs, M.; Graf, G.

    2009-02-01

    A laboratory flume channel, equipped with an acoustic Doppler flow sensor and a bottom scanning laser, was used for detailed, non-intrusive flow measurements (at 2 cm s - 1 and 10 cm s - 1 ) around solitary biogenic structures, combined with high-resolution mapping of the structure shape and position. The structures were replicates of typical macrozoobenthic species commonly found in the Mecklenburg Bight and with a presumed influence on both, the near-bed current regime and sediment transport dynamics: a worm tube, a snail shell, a mussel, a sand mound, a pit, and a cross-stream track furrow. The flow was considerably altered locally by the different protruding structures (worm tube, snail, mussel and mound). They reduced the horizontal approach velocity by 72% to 79% in the wake zone at about 1-2 cm height, and the flow was deflected around the structures with vertical and lateral velocities of up to 10% and 20% of the free-stream velocity respectively in a region adjacent to the structures. The resulting flow separation (at flow Reynolds number of about 4000 and 20,000 respectively) divided an outer deflection region from an inner region with characteristic vortices and the wake region. All protruding structures showed this general pattern, but also produced individual characteristics. Conversely, the depressions (track and pit) only had a weak influence on the local boundary layer flow, combined with a considerable flow reduction within their cavities (between 29% and 53% of the free-stream velocity). A longitudinal vortex formed, below which a stagnant space was found. The average height affected by the structure-related mass flow rate deficit for the two velocities was 1.6 cm and 1.3 cm respectively (80% of height and 64%) for the protruding structures and 0.6 cm and 0.9 cm (90% and 127% of depth) for the depressions. Marine benthic soft-bottom macrozoobenthos species are expected to benefit from the flow modifications they induce, particularly in terms of

  3. A study of grout flow pattern analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S. Y. [Savannah River National Lab., Aiken, SC (United States); Hyun, S. [Mercer Univ., Macon, GA (United States)

    2013-01-10

    A new disposal unit, designated as Salt Disposal Unit no. 6 (SDU6), is being designed for support of site accelerated closure goals and salt nuclear waste projections identified in the new Liquid Waste System plan. The unit is cylindrical disposal vault of 380 ft diameter and 43 ft in height, and it has about 30 million gallons of capacity. Primary objective was to develop the computational model and to perform the evaluations for the flow patterns of grout material in SDU6 as function of elevation of grout discharge port, and slurry rheology. A Bingham plastic model was basically used to represent the grout flow behavior. A two-phase modeling approach was taken to achieve the objective. This approach assumes that the air-grout interface determines the shape of the accumulation mound. The results of this study were used to develop the design guidelines for the discharge ports of the Saltstone feed materials in the SDU6 facility. The focusing areas of the modeling study are to estimate the domain size of the grout materials radially spread on the facility floor under the baseline modeling conditions, to perform the sensitivity analysis with respect to the baseline design and operating conditions such as elevation of discharge port, discharge pipe diameter, and grout properties, and to determine the changes in grout density as it is related to grout drop height. An axi-symmetric two-phase modeling method was used for computational efficiency. Based on the nominal design and operating conditions, a transient computational approach was taken to compute flow fields mainly driven by pumping inertia and natural gravity. Detailed solution methodology and analysis results are discussed here.

  4. A study of grout flow pattern analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S. Y. [Savannah River National Lab., Aiken, SC (United States); Hyun, S. [Mercer Univ., Macon, GA (United States)

    2013-01-10

    A new disposal unit, designated as Salt Disposal Unit no. 6 (SDU6), is being designed for support of site accelerated closure goals and salt nuclear waste projections identified in the new Liquid Waste System plan. The unit is cylindrical disposal vault of 380 ft diameter and 43 ft in height, and it has about 30 million gallons of capacity. Primary objective was to develop the computational model and to perform the evaluations for the flow patterns of grout material in SDU6 as function of elevation of grout discharge port, and slurry rheology. A Bingham plastic model was basically used to represent the grout flow behavior. A two-phase modeling approach was taken to achieve the objective. This approach assumes that the air-grout interface determines the shape of the accumulation mound. The results of this study were used to develop the design guidelines for the discharge ports of the Saltstone feed materials in the SDU6 facility. The focusing areas of the modeling study are to estimate the domain size of the grout materials radially spread on the facility floor under the baseline modeling conditions, to perform the sensitivity analysis with respect to the baseline design and operating conditions such as elevation of discharge port, discharge pipe diameter, and grout properties, and to determine the changes in grout density as it is related to grout drop height. An axi-symmetric two-phase modeling method was used for computational efficiency. Based on the nominal design and operating conditions, a transient computational approach was taken to compute flow fields mainly driven by pumping inertia and natural gravity. Detailed solution methodology and analysis results are discussed here.

  5. Determination of caffeine using oscillating chemical reaction in a CSTR.

    Science.gov (United States)

    Gao, Jinzhang; Ren, Jie; Yang, Wu; Liu, XiuHui; Yang, Hua

    2003-07-14

    A new analytical method for the determination of caffeine by the sequential perturbation caused by different amounts of caffeine on the oscillating chemical system involving the manganese(II)-catalyzed reaction between potassium bromate and tyrosine in acidic medium in a CSTR was proposed. The method exposed for the first time in this work. It relies on the relationship between the changes in the oscillation amplitude of the chemical system and the concentration of caffeine. The calibration curve fits a second-order polynomial equation very well when the concentration of caffeine over the range 4.0 x 10(-6) - 1.2 x 10(-4) M (r = 0.9968). The effect of influential variables, such as the concentration of reaction components, injection point, temperature, flow rate and stirring rate were studied. Some aspects of the potential mechanism of action of caffeine on the chemical oscillating system were also discussed. A real sample was determined and the result was satisfactory.

  6. Streamline topology: Patterns in fluid flows and their bifurcations

    DEFF Research Database (Denmark)

    Brøns, Morten

    2007-01-01

    Using dynamical systems theory, we consider structures such as vortices and separation in the streamline patterns of fluid flows. Bifurcation of patterns under variation of external parameters is studied using simplifying normal form transformations. Flows away from boundaries, flows close to fixed...

  7. Investigation of Turbulent Laminar Patterns in Poiseuille-Couette flow

    Science.gov (United States)

    Nguyen, Quoc; Papavassiliou, Dimitrios

    2014-11-01

    Laminar-turbulent intermittency has recently been observed in the transitional regime of pipe ... and plane Couette flow .... While many works focus on behavior of these patterns in plane Couette flow, little attention has been paid to Poiseuille flow and transition from Couette to Poiseuille flow. In this study, we investigate behavior of turbulent laminar patterns in Poiseuille-Couette flow, including pure Poiseuille and Couette flows at two limits. Direct Numerical Simulation (DNS) is used to simulate a Poiseuille-Couette channel at a size of 16 πh × 2h × 2 πh (corresponding to a resolution of 512 × 129 × 128 in x, y and z directions), with periodic boundary condition applied in the x and z directions (h is half of the channel height). The Reynolds number is 300, and the flow is at transitional regime in all simulations. Behavior of laminar turbulent patterns as the flow goes from Couette to Poiseuille flow will be presented in details. This would shed some light on the effect of different types of flow on these patterns, as well as how these patterns vary from fully Poiseuille flow to fully Couette flow.

  8. Correlation between permeability and groundwater flow patterns in carbonate rocks

    Science.gov (United States)

    Park, Y.; Lee, J.; Park, Y.; Keehm, Y.

    2011-12-01

    Groundwater flow in carbonate rocks is controlled by many factors such as degree of fracture and pore development, weathering and diagenesis. Among these factors, fracture is main factor and can form main flow path. Also, flow patterns in carbonate area are decided by these factors. This study was performed to understand factors controlling permeability and flow patterns in carbonate area and to evaluate correlation between permeability and flow patterns. Data used in this study were collected from many literatures and these data were analyzed and evaluated using graphic and statistical analysis. In many carbonate areas, branching conduit patterns were dominant. Of these areas, permeability was relatively high in areas where moving distance of flow was short and hydraulic gradient was steep. This work was supported by the Energy Resources R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2009201030001A).

  9. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    Science.gov (United States)

    Dukler, A. E.; Fabre, J. A.; Mcquillen, J. B.; Vernon, R.

    1987-01-01

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  10. The flow patterning capability of localized natural convection.

    Science.gov (United States)

    Huang, Ling-Ting; Chao, Ling

    2016-09-14

    Controlling flow patterns to align materials can have various applications in optics, electronics, and biosciences. In this study, we developed a natural-convection-based method to create desirable spatial flow patterns by controlling the locations of heat sources. Fluid motion in natural convection is induced by the spatial fluid density gradient that is caused by the established spatial temperature gradient. To analyze the patterning resolution capability of this method, we used a mathematical model combined with nondimensionalization to correlate the flow patterning resolution with experimental operating conditions. The nondimensionalized model suggests that the flow pattern and resolution is only influenced by two dimensionless parameters, and , where Gr is the Grashof number, representing the ratio of buoyancy to the viscous force acting on a fluid, and Pr is the Prandtl number, representing the ratio of momentum diffusivity to thermal diffusivity. We used the model to examine all of the flow behaviors in a wide range of the two dimensionless parameter group and proposed a flow pattern state diagram which suggests a suitable range of operating conditions for flow patterning. In addition, we developed a heating wire with an angular configuration, which enabled us to efficiently examine the pattern resolution capability numerically and experimentally. Consistent resolutions were obtained between the experimental results and model predictions, suggesting that the state diagram and the identified operating range can be used for further application.

  11. Selenite and tellurite form mixed seleno- and tellurotrisulfides with CstR from Staphylococcus aureus

    OpenAIRE

    Luebke, Justin L.; Arnold, Randy J; Giedroc, David P.

    2013-01-01

    Staphylococcus aureus CstR (CsoR-like sulfur transferase repressor) is a member of the CsoR family of transition metal sensing metalloregulatory proteins. Unlike CsoR, CstR does not form a stable complex with transition metals but instead reacts with sulfite to form a mixture of di- and trisulfide species, CstR2(RS-SR′) and CstR2(RS-S-SR′)n, n = 1 or 2, respectively. Here, we investigate if CstR performs similar chemistry with related chalcogen oxyanions selenite and tellurite. In this work w...

  12. Patterns and instability of grannular flow

    Energy Technology Data Exchange (ETDEWEB)

    Ecke, Robert E [Los Alamos National Laboratory; Borzsonyi, Tamas [NON LANL; Mcelwaine, Jim N [U. CAMBRIDGE

    2009-01-01

    Dense granular flows are often observed to become unstable and form inhomogeneous structures in nature or industry. Although recently significant advances have been made in understanding simple flows, instabilities are often not understood in detail. We present experimental and numerical results that show the formation of longitudinal stripes. These arise from instability of the uniform flowing state of granular media on a rough inclined plane. The form of the stripes depends critically on the mean density of the flow with a robust form of stripes at high density that consists of fast sliding plug-like regions (stripes) on top of highly agitated boiling material -- a configuration reminiscent of the Leidenfrost effect when a droplet of liquid lifted by its vapor is hovering above a hot surface.

  13. Flow-pattern switching in a Motored Spark Ignition Engine

    CERN Document Server

    Abraham, Preeti S; Gupta, Saurabh; Kuo, Tang-Wei; Reuss, David L; Sick, Volker

    2014-01-01

    Cyclic-to-cycle variability, CCV, of intake-jet flow in an optical engine was measured using particle image velocimetry (PIV), revealing the possibility of two different flow patterns. A phase-dependent proper orthogonal decomposition (POD) analysis showed that one or the other flow pattern would appear in the average flow, sampled from test to test or sub-sampled within a single test; each data set contained individual cycles showing one flow pattern or the other. Three-dimensional velocity data from a large-eddy simulation (LES) of the engine showed that the PIV plane was cutting through a region of high shear between the intake jet and another large flow structure. Rotating the measurement plane 10{\\deg} revealed one or the other flow structure observed in the PIV measurements. Thus, it was hypothesized that cycle-to-cycle variations in the swirl ratio result in the two different flow patterns in the PIV plane. Having an unambiguous metric to reveal large-scale flow CCV, causes for this variability were ex...

  14. Regionalization of patterns of flow intermittence from gauging station records

    Science.gov (United States)

    Snelder, T. H.; Datry, T.; Lamouroux, N.; Larned, S. T.; Sauquet, E.; Pella, H.; Catalogne, C.

    2013-07-01

    Understanding large-scale patterns in flow intermittence is important for effective river management. The duration and frequency of zero-flow periods are associated with the ecological characteristics of rivers and have important implications for water resources management. We used daily flow records from 628 gauging stations on rivers with minimally modified flows distributed throughout France to predict regional patterns of flow intermittence. For each station we calculated two annual times series describing flow intermittence; the frequency of zero-flow periods (consecutive days of zero flow) in each year of record (FREQ; yr-1), and the total number of zero-flow days in each year of record (DUR; days). These time series were used to calculate two indices for each station, the mean annual frequency of zero-flow periods (mFREQ; yr-1), and the mean duration of zero-flow periods (mDUR; days). Approximately 20% of stations had recorded at least one zero-flow period in their record. Dissimilarities between pairs of gauges calculated from the annual times series (FREQ and DUR) and geographic distances were weakly correlated, indicating that there was little spatial synchronization of zero flow. A flow-regime classification for the gauging stations discriminated intermittent and perennial stations, and an intermittence classification grouped intermittent stations into three classes based on the values of mFREQ and mDUR. We used random forest (RF) models to relate the flow-regime and intermittence classifications to several environmental characteristics of the gauging station catchments. The RF model of the flow-regime classification had a cross-validated Cohen's kappa of 0.47, indicating fair performance and the intermittence classification had poor performance (cross-validated Cohen's kappa of 0.35). Both classification models identified significant environment-intermittence associations, in particular with regional-scale climate patterns and also catchment area, shape

  15. Flow Pattern and Heat Transfer Behavior of Boiling Two—Phase flow in Inclined Pipes

    Institute of Scientific and Technical Information of China (English)

    LiuDezhang; OuyangNing

    1992-01-01

    Movable Electrical Conducting Probe (MECP),a kind of simple and reliable measuring transducer,used for predicting full-flow-path flow pattern in a boiling vapor/liquid two-phase flow is introduced in this paper when the test pipe is set at different inclination angles,several kinds of flow patterns,such as bubble,slug,churn,intermittent,and annular flows,may be observed in accordance with the locations of MECP.By means of flow pattern analysis,flow fleld numerical calculations have been carried out,and heat transfer coeffcient correlations along full-flow-path derived.The results show that heat transfer performance of boiling two-phase flow could be significanfly augmanted as expected in some flow pattern zones.The results of the investigation,measuring techniques and conclusions contained in this paper would be a useful reference in foundational research for prediction of flow pattern and heat transfer behavior in boiling two-phase flow,as well as for turbine vane liquid-cooling design.

  16. Spatio-temporal flow pattern observations using bio-inspired hair flow sensors

    NARCIS (Netherlands)

    Dagamseh, Ahmad; Hmeidi, Sarah; Krijnen, Gijs

    2015-01-01

    In nature, sensing is a fundamental property of virtually all living creatures. For many insects airflow patterns, as observed by means of their hair-sensors, carry highly valuable information exposing the sources of these flows. Flow-sensor arrays can be used to extract spatio-temporal flow fields

  17. Scale invariance of subsurface flow patterns and its limitation

    Science.gov (United States)

    Hergarten, S.; Winkler, G.; Birk, S.

    2016-05-01

    Preferential flow patterns in the subsurface are of great importance for the availability and the quality of water resources. However, knowledge of their spatial structure is still behind their importance, so that understanding the nature of preferential flow patterns is a major issue in subsurface hydrology. Comparing the statistics of river catchment sizes and spring discharges, we found that the morphology of preferential subsurface flow patterns is probably scale invariant and similar to that of dendritic river networks. This result is not limited to karstic aquifers where the occurrence of dendritic structures has been known at least qualitatively for a long time. The scale invariance even seems to be independent of the lithology of the aquifer. However, scale invariance of river patterns seems to be only limited by the continental scale, while scale invariance of subsurface flow patterns breaks down at much smaller scales. The upper limit of scale invariance in subsurface flow patterns is highly variable. We found a range from thousands of square kilometers for limestone aquifers down to less than 1 km2 in the weathered zone and debris accumulations of crystalline rocks.

  18. Altered doppler flow patterns in cirrhosis patients: An overview

    Energy Technology Data Exchange (ETDEWEB)

    Iranpour, Pooya; Lall, Chandana; Houshyar, Roozbeh; Helmy, Mohammad; Yang, Albert; Ward, Garrett; Goodwin, Scott C. [Dept. of Radiology, University of California Irvine, Orange (United States); Choi, Joon Il [Dept. of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of)

    2016-01-15

    Doppler ultrasonography of the hepatic vasculature is an integral part of evaluating precirrhotic and cirrhotic patients. While the reversal of the portal venous flow is a well-recognized phenomenon, other flow patterns, although not as easily understood, may play an important role in assessing the disease status. This article discusses the different characteristic flow patterns observed from the portal vein, hepatic artery, and hepatic vein in patients with liver cirrhosis or related complications and procedures. Knowledge of these different flow patterns provides additional information that may reinforce the diagnosis of cirrhosis, help in staging, and offer prognostic information for determining the direction of therapy. Doppler ultrasonography is invaluable when liver transplantation is being considered and aids in the diagnosis of cirrhosis and portal hypertension.

  19. Implementation of Neural Control for Continuous Stirred Tank Reactor (CSTR

    Directory of Open Access Journals (Sweden)

    Karima M. Putrus

    2011-01-01

    Full Text Available In this paper a dynamic behavior and control of a jacketed continuous stirred tank reactor (CSTR is developed using different control strategies, conventional feedback control (PI and PID, and neural network (NARMA-L2, and NN Predictive control. The dynamic model for CSTR process is described by a first order lag system with dead time.The optimum tuning of control parameters are found by two different methods; Frequency Analysis Curve method (Bode diagram and Process Reaction Curve using the mean of Square Error (MSE method. It is found that the Process Reaction Curve method is better than the Frequency Analysis Curve method and PID feedback controller is better than PI feedback controller. The results show that the artificial neural network is the best method to control the CSTR process and it is better than the conventional method because it has smaller value of mean square error (MSE. MATLAB program is used as a tool of solution for all cases used in the present work.

  20. The Helical Oscillating Heat Pipe: Flow Pattern Behaviour Study

    Directory of Open Access Journals (Sweden)

    Y. Sriudom

    2015-01-01

    Full Text Available This research aims to study the effect of evaporator temperature, pitch distance, and working fluid on the internal flow pattern and the heat transfer characteristics of the helical oscillating heat pipe. A Pyrex tube with an inner diameter of 2.4 mm was used to study the flow pattern in the evaporator section. The pitch distance varied at 1, 1.5, and 2 cm. Water and R-123 were used as working fluid with a filling ratio of 80% by total volume. In the evaporator section, the water temperature varied at 60, 75, and 90°C to supply heat to the heat pipe. In the condenser section, air with a temperature of 25°C was used as heat sink. From the results, it was found that 4 internal flow patterns, bubble flow, slug flow, annular flow, and stratified wavy flow, were observed in the evaporator section for both working fluids. The heat transfer rate decreased when the pitch distance was increased from 1 to 2 cm. The maximum heat flux was 2,132.6 and 1,773.4 W/m2 for the working fluid of R-123 and water, respectively. Both occurred at a pitch distance of 1 cm and an evaporator temperature of 90°C.

  1. FLOW PATTERNS AND FORCE CHARACTERISTICS OF LAMINAR FLOW PAST FOUR CYLINDERS IN DIAMOND ARRANGEMENT

    Institute of Scientific and Technical Information of China (English)

    ZOU Lin; LIN Yu-feng; LU Hong

    2011-01-01

    A three-dimensional numerical investigation of cross-flow past four circular cylinders in a diamond arrangement at Reynolds number of 200 is carried out. With the spacing ratios ( L/D ) ranging from 1.2 to 5.0, the flow patterns can be classified into three basic regimes. The critical spacing ratio for the transition from narrow gap flow pattern to vortex impingement flow pattern around the cylinders is found to be L/D = 3.0, while a single bluff-body flow pattern is observed at L/D = 1.2. The relationship between the three-dimensional flow patterns and force characteristics around the four cylinders shows that the variation of forces and Strouhal numbers against L/D are generally governed by these three kinds of flow patterns. It is concluded that the spacing ratio has important effects on the development of the free shear layers about the cylinders and hence has significant effects on the force and pressure characteristics of the four cylinders with different spacing ratios.

  2. Patterning electrohydrodynamic flows with conductive obstacles in microfluidic channels.

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Tyrone F.; Simmons, Blake Alexander; Barrett, Louis C.; Cummings, Eric B.; Fiechtner, Gregory J.; Harnett, Cindy K.; Skulan, Andrew J.

    2005-03-01

    Flow patterns with both recirculating and unidirectional characteristics are useful for controlled mixing and pumping within microfluidic devices. We have developed a fabrication process that converts injection-molded polymer chips into devices that demonstrate induced-charge electroosmosis (ICEO) effects (1,2) in AC fields. Polymeric insulating posts are coated with metal to produce a nonuniform zeta potential under an applied electric field. Induced flows are analyzed by particle image velocimetry. Stable, recirculating flow patterns are discussed, along with their potential to produce well-characterized and reversible streamlines for on-chip mixing in chemical separation and synthesis devices. Asymmetric conductive features can bias the flow direction, generating unidirectional pumping in an AC field. This pumping approach will be discussed in comparison with DC electrokinetic pumps we have studied.

  3. Treatment of solutions with binary solutes using an admicellar enhanced CSTR: background solute effect.

    Science.gov (United States)

    Lee, Chon-Lin; Lee, Jiu-Chang

    2002-04-01

    This study presents an admicellar enhanced continuous-flow stirred tank reactor (CSTR). Solutions containing single and binary aliphatic alcohols are introduced into this reactor for breakthrough experiments. Two phenomena occur during experiments with binary solutes: (a) a competitive effect caused by background solutes with relatively high hydrophobicity; (b) a co-solvent effect attributable to background solutes with relatively low hydrophobicity. The competition phenomenon and the corresponding mechanism involved are well demonstrated by directly monitoring the pre-adsolubilized solutes drawn out back to the solution while adsolubilizing other solutes with higher hydrophobicity. On the other hand, adsolubilization kinetics hindered by the background solute, which acts as a co-solvent, significantly alters the slopes of breakthrough curves of the target solute treated in the reactor.

  4. Effect of post-digestion temperature on serial CSTR biogas reactor performance

    DEFF Research Database (Denmark)

    Boe, Kanokwan; Karakashev, Dimitar Borisov; Trably, Eric

    2009-01-01

    The effect of post-digestion temperature on a lab-scale serial continuous-flow stirred tank reactor (CSTR) system performance was investigated. The system consisted of a main reactor operated at 55 degrees C with hydraulic retention time (HRT) of 15 days followed by post-digestion reactors with HRT...... of 5.3 days. Three post-digestion temperatures (55 degrees C, 37 degrees C and 15 degrees C) were compared in terms of biogas production, process stability, microbial community and methanogenic activity, The results showed that the post-digesters operated at 55 degrees C, 37 degrees C and 15 degrees C...... gave extra biogas production of 11.7%, 8.4% and 1.2%, respectively. The post-digester operated at 55 degrees C had the highest biogas production and was the most stable in terms of low VFA concentrations. The specific methanogenic activity tests revealed that the main reactor and the post-digester...

  5. Regionalization of patterns of flow intermittence from gauging station records

    Directory of Open Access Journals (Sweden)

    T. H. Snelder

    2013-07-01

    Full Text Available Understanding large-scale patterns in flow intermittence is important for effective river management. The duration and frequency of zero-flow periods are associated with the ecological characteristics of rivers and have important implications for water resources management. We used daily flow records from 628 gauging stations on rivers with minimally modified flows distributed throughout France to predict regional patterns of flow intermittence. For each station we calculated two annual times series describing flow intermittence; the frequency of zero-flow periods (consecutive days of zero flow in each year of record (FREQ; yr−1, and the total number of zero-flow days in each year of record (DUR; days. These time series were used to calculate two indices for each station, the mean annual frequency of zero-flow periods (mFREQ; yr−1, and the mean duration of zero-flow periods (mDUR; days. Approximately 20% of stations had recorded at least one zero-flow period in their record. Dissimilarities between pairs of gauges calculated from the annual times series (FREQ and DUR and geographic distances were weakly correlated, indicating that there was little spatial synchronization of zero flow. A flow-regime classification for the gauging stations discriminated intermittent and perennial stations, and an intermittence classification grouped intermittent stations into three classes based on the values of mFREQ and mDUR. We used random forest (RF models to relate the flow-regime and intermittence classifications to several environmental characteristics of the gauging station catchments. The RF model of the flow-regime classification had a cross-validated Cohen's kappa of 0.47, indicating fair performance and the intermittence classification had poor performance (cross-validated Cohen's kappa of 0.35. Both classification models identified significant environment-intermittence associations, in particular with regional-scale climate patterns and also

  6. Identification of a Typical CSTR Using Optimal Focused Time Lagged Recurrent Neural Network Model with Gamma Memory Filter

    National Research Council Canada - National Science Library

    Naikwad, S. N; Dudul, S. V

    2009-01-01

    .... It is noticed from literature review that process control of CSTR using neuro-fuzzy systems was attempted by many, but optimal neural network model for identification of CSTR process is not yet available...

  7. Flow Patterns and Thermal Drag in Supersonic Duct Flow with Heating

    Institute of Scientific and Technical Information of China (English)

    Zeng-YuanGuo; Zhi-HongLiu

    1994-01-01

    The supersonic duct flow with fixed back pressure to stagnation pressure ratio Pb/P0 under heating is investigated analytically.A “Flow Pattern Diagram” Which consists of six pattern zones is developed.By this diagram the actual flow state in supersonic duct flow system can be determined conveniently when Pb/Po and heating intensity are knows.It is impossible for flow with heavy heating to become supersonic,even though the pressure ratio is much smaller than the critical pressure ratio,Based on the analogy between viscous effect and heating effect a thermal drag factor has een defined.which can predict the flow property variation due to heating and the relaive importance of viscous effect and heating effect.

  8. Patterns of regional cerebral blood flow in acute stroke

    DEFF Research Database (Denmark)

    Olsen, T S; Skriver, E B

    1981-01-01

    In a consecutive group of 56 stroke patients the regional cerebral blood flow was measured within 84 hours after stroke. A 254 multidetector scintillation camera and the intracarotid Xenon-133 injection method was used to study rCBF. Typical rCBF-patterns are described and compared to the findings...

  9. Modeling of the expiratory flow pattern of spontaneously breathing cats

    NARCIS (Netherlands)

    Walraven, D; van der Grinten, CPM; Bogaard, JM; van der Ent, CK; Luijendijk, SCM

    2003-01-01

    A mathematical model was developed describing the entire expiratory flow pattern during spontaneous, tidal breathing in the absence of expiratory muscle activity. It provides estimates for the time constants of the respiratory System (tauRS(model)) and of the decay of continuing inspiratory muscle a

  10. Turbulent-laminar patterns in plane Poiseuille flow

    CERN Document Server

    Tuckerman, Laurette S; Schrobsdorff, Hecke; Schneider, Tobias M; Gibson, John F

    2014-01-01

    Turbulent-laminar banded patterns in plane Poiseuille flow are studied via direct numerical simulations in a tilted and translating computational domain using a parallel version of the pseudospectral code Channelflow. 3D visualizations via the streamwise vorticity of an instantaneous and a time-averaged pattern are presented, as well as 2D visualizations of the average velocity field and the turbulent kinetic energy. Simulations for Reynolds numbers descending from 2300 to 700 show the gradual development from uniform turbulence to a pattern with wavelength 20 half-gaps near Re=1900, to a pattern with wavelength 40 near Re=1300 and finally to laminar flow near Re=800. These transitions are tracked quantitatively via diagnostics using the amplitude and phase of the Fourier transform and its probability distribution. The propagation velocity of the pattern is approximately that of the mean flux and is a decreasing function of Reynolds number. Examination of the time-averaged flow shows that a turbulent band is ...

  11. Flow Visualization and Pattern Formation in Vertically Falling Liquid Films

    Science.gov (United States)

    Balakotaiah, Vemuri; Malamataris, Nikolaos

    2008-11-01

    Analytical results of a low-dimensional two equation h-q model and results of a direct numerical simulation of the transient two-dimensional Navier Stokes equations are presented for vertically falling liquid films along a solid wall. The numerical study aims at the elucidation of the hydrodynamics of the falling film. The analytical study aims at the calculation of the parameter space where pattern formation occurs for this flow. It has been found that when the wave amplitude exceeds a certain magnitude, flow reversal occurs in the film underneath the minimum of the waves [1]. The instantaneous vortical structures possess two hyperbolic points on the vertical wall and an elliptic point in the film. As the wave amplitude increases further, the elliptic point reaches the free surface of the film and two more hyperbolic points are formed in the free surface that replace the elliptic point. Between the two hyperbolic points on the free surface, the streamwise component of velocity is negative and the film is divided into asymmetric patterns of up and down flows. Depending on the value of the Kapitza number, these patterns are either stationary or oscillatory. Physical reasons for the influence of the Kapitza number on pattern formation are given. Movies are shown where the pattern formation is demonstrated. [1] N.A.Malamataris and V.Balakotaiah (2008), AIChE J., 54(7), p. 1725-1740

  12. Turbulent patterns in wall-bounded flows: a Turing instability?

    CERN Document Server

    Manneville, Paul

    2012-01-01

    In their way to/from turbulence, plane wall-bounded flows display an interesting transitional regime where laminar and turbulent oblique bands alternate, the origin of which is still mysterious. In line with Barkley's recent work about the pipe flow transition involving reaction-diffusion concepts, we consider plane Couette flow in the same perspective and transform Waleffe's classical four-variable model of self-sustaining process into a reaction-diffusion model. We show that, upon fulfillment of a condition on the relative diffusivities of its variables, the featureless turbulent regime becomes unstable against patterning as the result of a Turing instability. A reduced two-variable model helps us to delineate the appropriate region of parameter space. An {\\it intrinsic} status is therefore given to the pattern's wavelength for the first time. Virtues and limitations of the model are discussed, calling for a microscopic support of the phenomenological approach.

  13. Subcutaneous blood flow in early male pattern baldness

    Energy Technology Data Exchange (ETDEWEB)

    Klemp, P.; Peters, K.; Hansted, B.

    1989-05-01

    The subcutaneous blood flow (SBF) was measured by the /sup 133/Xe washout method in the scalp of 14 patients with early male pattern baldness. Control experiments were performed in 14 normal haired men matched for age. The SBF in the scalp of the normal individuals was about 10 times higher than previously reported SBF values in other anatomical regions. In patients with early male pattern baldness, SBF was 2.6 times lower than the values found in the normal individuals (13.7 +/- 9.6 vs 35.7 +/- 10.5 ml/100 g/min-1). This difference was statistically significant (p much less than 0.001). A reduced nutritive blood flow to the hair follicles might be a significant event in the pathogenesis of early male pattern baldness.

  14. Comparison of detection pattern of HCC by ferumoxide-enhanced MRI and intratumoral blood flow pattern

    Energy Technology Data Exchange (ETDEWEB)

    Itou, Naoki; Kotake, Fumio [Tokyo Medical Coll., Ami, Ibaraki (Japan). Kasumigaura Hospital; Saitou, Kazuhiro; Abe, Kimihiko

    2000-08-01

    We compared the detection rate and pattern of ferumoxide-enhanced magnetic resonance imaging (Fe-MRI) with the intratumoral blood flow pattern determined by CT angiography (CTA) and CT portography (CTAP) in 124 nodes (34 cases) diagnosed as hepatocellular carcinoma (HCC) or borderline HCC, based on the clinical course. Sequences to obtain a T1-weighted images (T1W), proton density-weighted images (PDW), T2-weighted images (T2W), T2*-weighted images (T2*W) were used in Fe-MRI. In nodes shown to be hypervascular on CTA, the detection rate by Fe-MRI was 69.7%. In nodes shown to be avascular by CTAP, the detection rate by Fe-MRI was 67.3%. These rates were higher than with other flow patterns. In nodes showing high signal intensity (HSI) on any sequences, arterial blood flow was increased and portal blood flow decreased in comparison with nodes without high signal intensity. All nodes showing HSI, both on Fe-MRI T2W and T2*W, were hypervascular on CTA, and portal blood flow was absent on CTAP. Nodes showing HSI on both T2*W and T2W were considered to have greater arterial blood flow and decreased portal blood flow compared with nodes appearing as HSI on T2*W, but only as iso- or low signal intensity on T2W (Mann-Whitney U-test; p<0.05). (author)

  15. Two-phase flow patterns for flow condensation in small-diameter tubes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two-phase flow patterns have been observed visually to investigate the effects of tube diameter, mass flux and tube inclination on flow condensation in small-diameter tubes. For horizontal or inclined small-diameter tubes, gravity-domination is decreased by shear stress and surface tension on phase change interface, which weakens the stratification of condensate and vapor flow due to the action of gravity perpendicular to flow direction. As decreasing the tube diameter from 5.79 mm to 2.18 mm, the annular or sub-annular flows become prevailing in flow regime map. The existing flow regime maps for macro scale cannot predict the experimental data in the present study.

  16. NUMERICAL SIMULATION OF FLOW PATTERNS IN PLANAR JETS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two-dimensional spatial developing turbulent planar jets with different velocity ratios of jet fluid to co-flow fluid at the inlet section are simulated with large eddy simulation give detailed information of transient behaviors of coherent structures in turbulent jets and depict how the velocity ratios will affect the evolution of coherent structures. The motion of small-scale structures is described by the standard Smagorinsky SGS model. Transport equation of passive scalar is also solved in order to perform numerical visualization of flow field. Transient distributions of velocity are obtained at different evolution periods of turbulent jets. Evolutions of coherent structures in flow field are also given in this paper as well as the comparison of flow patterns among three different velocity ratios.``

  17. Pattern formation in directional solidification under shear flow. I. Linear stability analysis and basic patterns.

    Science.gov (United States)

    Marietti, Y; Debierre, J M; Bock, T M; Kassner, K

    2001-06-01

    An asymptotic interface equation for directional solidification near the absolute stability limit is extended by a nonlocal term describing a shear flow parallel to the interface. In the long-wave limit considered, the flow acts destabilizing on a planar interface. Moreover, linear stability analysis suggests that the morphology diagram is modified by the flow near onset of the Mullins-Sekerka instability. Via numerical analysis, the bifurcation structure of the system is shown to change. Besides the known hexagonal cells, structures consisting of stripes arise. Due to its symmetry-breaking properties, the flow term induces a lateral drift of the whole pattern, once the instability has become active. The drift velocity is measured numerically and described analytically in the framework of a linear analysis. At large flow strength, the linear description breaks down, which is accompanied by a transition to flow-dominated morphologies which is described in the following paper. Small and intermediate flows lead to increased order in the lattice structure of the pattern, facilitating the elimination of defects. Locally oscillating structures appear closer to the instability threshold with flow than without.

  18. Selenite and tellurite form mixed seleno- and tellurotrisulfides with CstR from Staphylococcus aureus.

    Science.gov (United States)

    Luebke, Justin L; Arnold, Randy J; Giedroc, David P

    2013-04-01

    Staphylococcus aureus CstR (CsoR-like sulfur transferase repressor) is a member of the CsoR family of transition metal sensing metalloregulatory proteins. Unlike CsoR, CstR does not form a stable complex with transition metals but instead reacts with sulfite to form a mixture of di- and trisulfide species, CstR2(RS-SR') and CstR2(RS-S-SR')n)n=1 or 2, respectively. Here, we investigate if CstR performs similar chemistry with related chalcogen oxyanions selenite and tellurite. In this work we show by high resolution tandem mass spectrometry that CstR is readily modified by selenite (SeO3(2-)) or tellurite (TeO3(2-)) to form a mixture of intersubunit disulfides and selenotrisulfides or tellurotrisulfides, respectively, between Cys31 and Cys60'. Analogous studies with S. aureus CsoR reveals no reaction with selenite and minimal reaction with tellurite. All cross-linked forms of CstR exhibit reduced DNA binding affinity. We show that Cys31 initiates the reaction with sulfite through the formation of S-sulfocysteine (RS-SO3(2-)) and Cys60 is required to fully derivatize CstR to CstR2(RS-SR') and CstR2(RS-S-SR'). The modification of Cys31 also drives an allosteric switch that negatively regulates DNA binding while derivatization of Cys60 alone has no effect on DNA binding. These results highlight the differences between CstRs and CsoRs in chemical reactivity and metal ion selectivity and establish Cys31 as the functionally important cysteine residue in CstRs.

  19. Mean flow of turbulent-laminar patterns in plane Couette flow

    CERN Document Server

    Barkley, D; Barkley, Dwight; Tuckerman, Laurette S.

    2007-01-01

    A turbulent-laminar banded pattern in plane Couette flow is studied numerically. This pattern is statistically steady, is oriented obliquely to the streamwise direction, and has a very large wavelength relative to the gap. The mean flow, averaged in time and in the homogeneous direction, is analysed. The flow in the quasi-laminar region is not the linear Couette profile, but results from a non-trivial balance between advection and diffusion. This force balance yields a first approximation to the relationship between the Reynolds number, angle, and wavelength of the pattern. Remarkably, the variation of the mean flow along the pattern wavevector is found to be almost exactly harmonic: the flow can be represented via only three cross-channel profiles as U(x,y,z) = U_0(y) + U_c(y) cos(kz) + U_s(y) sin(kz). A model is formulated which relates the cross-channel profiles of the mean flow and of the Reynolds stress. Regimes computed for a full range of angle and Reynolds number in a tilted rectangular periodic compu...

  20. Effect of a flow-corrective insert on the flow pattern in a pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yu; Gui, Nan; Yang, Xingtuan [Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084 (China); Tu, Jiyuan [Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084 (China); School of Aerospace, Mechanical & Manufacturing Engineering, RMIT University, Melbourne 3083, VIC (Australia); Jiang, Shengyao, E-mail: shengyaojiang@sina.com [Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084 (China)

    2016-04-15

    Highlights: • Effect of an insert on improving flow uniformity and eliminating stagnant zone is studied. • Three values concerned with the stagnant zone, radial uniformity and flow sequence are used. • Outlet diameter is a critical parameter that determines balancing mechanism of the insert. • Height/location is varied to let the insert work in unbalanced region and avoid adverse effect. - Abstract: A flow-corrective insert is adopted in the pebble-bed high temperature gas-cooled reactor (HTGR) to improve flow performance of the pebble flow for the first time. 3D discrete element method (DEM) modeling is employed to study this slow and dense granular flow. It is verified that locating a properly designed insert in the bed can help transform unsatisfactory flow field to the preferred flow pattern for pebble bed reactors. Three characteristic values on the stagnant zone, radial uniformity and flow sequence of pebble flow are defined to evaluate uniformity of the overall flow field quantitatively. The results demonstrate that the pebble bed equipped with an insert performs better than normal beds from all these three aspects. Moreover, based on numerical experiments, several universal tips for insert design on height, location and outlet diameter are suggested.

  1. Identifiability analysis of the CSTR river water quality model.

    Science.gov (United States)

    Chen, J; Deng, Y

    2006-01-01

    Conceptual river water quality models are widely known to lack identifiability. The causes for that can be due to model structure errors, observational errors and less frequent samplings. Although significant efforts have been directed towards better identification of river water quality models, it is not clear whether a given model is structurally identifiable. Information is also limited regarding the contribution of different unidentifiability sources. Taking the widely applied CSTR river water quality model as an example, this paper presents a theoretical proof that the CSTR model is indeed structurally identifiable. Its uncertainty is thus dominantly from observational errors and less frequent samplings. Given the current monitoring accuracy and sampling frequency, the unidentifiability from sampling frequency is found to be more significant than that from observational errors. It is also noted that there is a crucial sampling frequency between 0.1 and 1 day, over which the simulated river system could be represented by different illusions and the model application could be far less reliable.

  2. Evoluton of polygonal fracture patterns in lava flows.

    Science.gov (United States)

    Aydin, A; Degraff, J M

    1988-01-29

    Cooling-induced fractures, also known as columnar joints, divide basaltic lava flows into prismatic columns with polygonal cross sections. The regularity and symmetry of the fracture patterns have long fascinated naturalists. In view of the recent selection of two candidate nuclear waste sites in areas where polygonally fractured volcanic rocks are located, a better understanding of the fracture patterns is required. Field data indicate that the tetragonal networks at flow surfaces evolve systematically to hexagonal networks as the joints grow inward during solidification of lava. This evolution occurs by the gradual change of most orthogonal intersections to nonorthogonal intersections of about 120 degrees. The surface features and intersection geometries of columnar joints show that joint segments at any given level form sequentially yet harmoniously.

  3. Influence of boundaries on pattern selection in through-flow

    CERN Document Server

    Roth, D R; Lücke, M; Müller, H W; Kamps, M; Schmitz, R

    1996-01-01

    The problem of pattern selection in absolutely unstable open flow systems is investigated by considering the example of Rayleigh-Bénard convection. The spatiotemporal structure of convection rolls propagating downstream in an externally imposed flow is determined for six different inlet/outlet boundary conditions. Results are obtained by numerical simulations of the Navier-Stokes equations and by comparison with the corresponding Ginzburg-Landau amplitude equation. A unique selection process is observed being a function of the control parameters and the boundary conditions but independent of the history and the system length. The problem can be formulated in terms of a nonlinear eigen/boundary value problem where the frequency of the propagating pattern is the eigenvalue. PACS: 47.54.+r, 47.20.Bp, 47.27.Te, 47.20.Ky

  4. Microscopic Current Flow Patterns in Nanoscale Quantum Point Contacts

    Science.gov (United States)

    Sai, Na; Bushong, Neil; Hatcher, Ryan; di Ventra, Massimiliano

    2006-03-01

    Transport in nanoscale conductors has been studied extensively mainly using the stationary scattering approach. However, the dynamical nature of transport, and in particular, the flow patterns of the microscopic current through a nanoscale junction, have remained poorly understood. We apply a novel time-dependent transport approach [1], which combines closed and finite geometries with time-dependent density functional theory,to study current flow patterns in nanoscale quantum point contacts [2]. The results of both atomistic and jellium calculations show that surface charges form dynamically at the junction-electrode interfaces in both abrupt and adiabatic junctions. The curr ent exhibits some characteristics of a classical hydrodynamic liquid but also displays unique patterns arising from the interaction with the surface charges. We also investigate the effect of the flow velocity, charge density, and lattice structures on the electron dynamics. If time permits we also discuss the effects of the viscosity of the electron liquid [3]. Work supported by DOE (DE-FG02-05ER46204). [1] M. Di Ventra and T.N. Todorov, J. Phys. Cond. Matt. 16, 8025 (2004). [2] N. Bushong, N. Sai and, M. Di Ventra, Nano Lett. (in press). [3] N. Sai, M. Zwolak, G. Vignale, and M. Di Ventra, Phys. Rev. Lett. 94, 186810 (2005 ).

  5. Aging and transmitral flow pattern in patients with systemic hypertension.

    Science.gov (United States)

    Kishida, Yukari; Tanaka, Nobuaki; Ezumi, Tomoko; Hadano, Yasuyuki; Akagawa, Eizo; Hashimoto, Ryo; Kunichika, Hideki; Murata, Kazuya; Hinoda, Yuji; Matsuzaki, Masunori

    2006-12-01

    Currently, the transmitral flow (TMF) pattern is routinely recorded as the first step in the assessment of left ventricular diastolic function. In young, healthy subjects, it is known that the early diastolic flow (E wave) of TMF is larger than the late diastolic flow (A wave). The E/A ratio then gradually decreases with age. This change in the pattern of TMF can be expected to occur earlier in patients with systemic hypertension than in healthy subjects. However, data pertaining to this matter are limited for Japanese patients. The purpose of this study was to investigate the changing pattern of TMF with age in Japanese patients with systemic hypertension. A database of echocardiographic examination reports was surveyed. A total of 553 patients with systemic hypertension (HT group) and 394 patients without hypertension or organic heart disease (control group) were included in this study. The patients were subdivided according to age, after which the E/A ratio was compared for different patient categories and age groups. The E/A ratio gradually decreased with age in the control group, and the mean value of E/A was <1 in the sixth decade. On the other hand, the E/A ratio rapidly decreased and was <1 in the fifth decade in the HT group. In patients in the HT group, the E/A ratio decreased about a decade earlier compared with patients in the control group.

  6. Flow Pattern Identification of Horizontal Two-Phase Refrigerant Flow Using Neural Networks

    Science.gov (United States)

    2015-12-31

    of several flow patterns which may include bubbly, plug, slug, stratified-wavy, and annular flows [17]. Here, previous work is extended by including...liquid (εf) alone. Since non- linear electric field responses may generate values outside the normalizedElectrode Insulation Measurement Volume 1 2 3 8 7...this work, the linear back projection algorithm was used in the software provided by the instrumentmanufacturer for the tomographic reconstruction

  7. Animating streamlines with repeated asymmetric patterns for steady flow visualization

    Science.gov (United States)

    Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

    2012-01-01

    Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

  8. Noise induced pattern formation of oscillation growth in traffic flow

    CERN Document Server

    Tian, Junfang; Treiber, Martin

    2016-01-01

    Noise is able to induce diverse patterns in physical and interdisciplinary extended systems. This Letter investigates the role of noise in pattern formation of traffic flow, which is a typical self-driven system far from equilibrium. We demonstrate that noise is necessary to correctly describe the observed spatiotemporal dynamics of growing traffic oscillation in the car following process. A heuristic analysis qualitatively explains the concave growth of the oscillation amplitude along the vehicles of a platoon. Based on this analysis, we propose a simple car-following model containing indifference regions and acceleration noise described by Brownian motion which reproduces well the experimental and empirical observations. Our study indicates that noise might also play an important role in pattern formation in other biological or socio-economic systems that are subject to stochasticity.

  9. The pattern of accretion flow onto Sgr A*

    CERN Document Server

    Czerny, M M T K D B

    2006-01-01

    The material accreting onto Sgr A* most probably comes from the nearby stars. We analyze the pattern of this flow at distances of a fraction of a parsec and we argue that the net angular momentum of this material is low but non-negligible, and the initially supersonic disk accretion changes into subsonic flow with constant angular momentum. Next we estimate the flow parameters at a distance $R_{BHL}$ from the black hole and we argue that for the plausible parameter range the accretion flow is non-stationary. The inflow becomes supersonic at distance of $\\sim 10^4 R_g$ but the solution does not continue below the horizon and the material piles up forming a torus, or a ring, at a distance of a few up to tens of Schwarzchild radii. Such a torus is known to be unstable and may explain strong variability of the flow in Sgr A*. Our considerations show that the temporary formation of such a torus seems to be unavoidable. Our best fitting model predicts a rather large accretion rate of around $4 \\cdot 10^{-6} M_{\\odo...

  10. On enzymatic pH oscillations in CSTR with outlet regulator

    Science.gov (United States)

    Ohmori, Takao; Yu, Weifang; Yamamoto, Takuji; Endo, Akira; Nakaiwa, Masaru; Amemiya, Takashi; Yamaguchi, Tomohiko

    2005-05-01

    The possibility of enzymatic pH oscillations is investigated for a CSTR with an outlet regulator. A linear stability analysis shows that no oscillation is possible in a CSTR without the regulator, using a proton-producing pH-dependent enzymatic reaction. However, self-sustained oscillations are found to occur in a CSTR, where the discharge of substrate is regulated at the outlet. The regions of oscillations in the parameter space are determined using a hydrolysis of N-α-benzoyl- L-arginine ethyl ester with papain. It is found that the region is quite large only when the substrate concentration in the outflow is kept at zero.

  11. Mathematical Modeling of Electrolyte Flow Dynamic Patterns and Volumetric Flow Penetrations in the Flow Channel over Porous Electrode Layered System in Vanadium Flow Battery with Serpentine Flow Field Design

    OpenAIRE

    Ke, Xinyou; Prahl, Joseph M.; Alexander, J. Iwan D.; Savinell, Robert F.

    2016-01-01

    In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in the flow channel over the porous electrode layered system in vanadium flow battery with serpentine flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic fl...

  12. Two-phase flow patterns in adiabatic and diabatic corrugated plate gaps

    Science.gov (United States)

    Polzin, A.-E.; Kabelac, S.; de Vries, B.

    2016-09-01

    Correlations for two-phase heat transfer and pressure drop can be improved considerably, when they are adapted to specific flow patterns. As plate heat exchangers find increasing application as evaporators and condensers, there is a need for flow pattern maps for corrugated plate gaps. This contribution presents experimental results on flow pattern investigations for such a plate heat exchanger background, using an adiabatic visualisation setup as well as a diabatic setup. Three characteristic flow patterns were observed in the considered range of two-phase flow: bubbly flow, film flow and slug flow. The occurrence of these flow patterns is a function of mass flux, void fraction, fluid properties and plate geometry. Two different plate geometries having a corrugation angle of 27° and 63°, respectively and two different fluids (water/air and R365mfc liquid/vapor) have been analysed. A flow pattern map using the momentum flux is presented.

  13. Experimental study of flow patterns and pressure drops of heavy oil-water-gas vertical flow

    Institute of Scientific and Technical Information of China (English)

    LIU Xi-mao; ZHONG Hai-quan; LI Ying-chuan; LIU Zhong-neng; WANG Qi

    2014-01-01

    A stainless steel apparatus of 18.5 m high and 0.05 m in inner diameter is developed, with the heavy oil from Lukeqin Xinjiang oil field as the test medium, to carry out the orthogonal experiments for the interactions between heavy oil-water and heavy oil-water-gas. With the aid of observation windows, the pressure drop signal can be collected and the general multiple flow patterns of heavy oil-water-gas can be observed, including the bubble, slug, churn and annular ones. Compared with the conventional oil, the bubble flows are identified in three specific flow patterns which are the dispersed bubble (DB), the bubble gas-bubble heavy oil go(B-B), and the bubble gas-intermittent heavy oilgo(B-I). The slug flows are identified in two specific flow patterns which are the intermittent gas-bubble heavy oilgo(I-B)and the intermittent gas-intermittent heavy oilgo(I-I). Compared with the observa- tions in the heavy oil-water experiment, it is found that the conventional models can not accurately predict the pressure gradient. And it is not water but heavy oil and water mixed phase that is in contact with the tube wall. So, based on the principle of the energy con- servation and the kinematic wave theory, a new method is proposed to calculate the frictional pressure gradient. Furthermore, with the new friction gradient calculation method and a due consideration of the flow characteristics of the heavy oil-water-gas high speed flow, a new model is built to predict the heavy oil-water-gas pressure gradient. The predictions are compared with the experiment data and the field data. The accuracy of the predictions shows the rationality and the applicability of the new model.

  14. Patterns, Instabilities, Colors, and Flows in Vertical Foam Films

    Science.gov (United States)

    Yilixiati, Subinuer; Wojcik, Ewelina; Zhang, Yiran; Pearsall, Collin; Sharma, Vivek

    2015-03-01

    Foams find use in many applications in daily life, industry and biology. Examples include beverages, firefighting foam, cosmetics, foams for oil recovery and foams formed by pollutants. Foams are collection of bubbles separated by thin liquid films that are stabilized against drainage by the presence of surfactant molecules. Drainage kinetics and stability of the foam are strongly influenced by surfactant type, addition of particles, proteins and polymers. In this study, we utilize the thin film interference colors as markers for identifying patterns, instabilities and flows within vertical foam films. We experimentally study the emergence of thickness fluctuations near the borders and within thinning films, and study how buoyancy, capillarity and gravity driven instabilities and flows, are affected by variation in bulk and interfacial physicochemical properties dependent on the choice of constituents.

  15. Controlling radial fingering patterns in miscible confined flows.

    Science.gov (United States)

    Chen, Ching-Yao; Huang, C-W; Wang, L-C; Miranda, José A

    2010-11-01

    Injection-driven immiscible flow in radial Hele-Shaw cells results in highly ramified patterns if the injection rate is constant in time. Likewise, time-dependent gap immiscible flow in lifting Hele-Shaw cells leads to intricate morphologies if the cell's gap width grows exponentially with time. Recent studies show that the rising of these complex fingered structures can be controlled by properly adjusting the injection rate, and the time-dependent gap width. We investigate the effectiveness of these control strategies assuming that the fluids involved are miscible. Despite the absence of surface tension effects, intensive numerical simulations support the stabilizing role of these controlling protocols. Splitting, merging and competition of fingers are all inhibited. The sensitivity of the system to changes in the initial conditions and Péclet numbers is also discussed.

  16. Intracardiac flow patterns in early embryonic life. A reexamination.

    Science.gov (United States)

    Yoshida, H; Manasek, F; Arcilla, R A

    1983-09-01

    Microangiography, using methylene blue injected at eight vitelline vein sites, was performed on 156 developing chick embryos at Hamburger-Hamilton stages 14-22. Two stream patterns were observed. Type A coursed sequentially through the dorsal portion of the sinus venosus, the cranial segments of the primitive atrium and atrioventricular canal, the ventral parts of the primitive ventricle and conus cordis, and, finally, the left branchial arches. Type B coursed through the ventral portion of the sinus venosus, the caudal segments of the primitive atrium and atrioventricular canal, the dorsal parts of the primitive ventricle and conus cordis, and, finally, the right branchial arches. Both streams flowed in parallel fashion in the conus cordis. At Hamburger-Hamilton stages 17-18, the dye stream from the right lateral vitelline vein was chiefly type A, whereas that from the left lateral vitelline vein was type B. At Hamburger-Hamilton stages 19-22, those patterns reversed, i.e., the right lateral vitelline vein stream ran as type B, whereas the left lateral vitelline vein stream assumed type A pattern. The cranial-caudal relationship of the two streams at the primitive atrium and atrioventricular canal is not consistent with the hypothesis that these streams separately expand the future right atrium and left atrium. Their parallel direction at the conus cordis does not support the theory that spiral septation is initiated by two spiral streams. The longitudinal separation of the two streams at and beyond the branchial arches also argues against aortico-pulmonary septation as a consequence of flow streaming. Our observations do not support the traditional flow-molding theory.

  17. Biotreatment of zinc-containing wastewater in a sulfidogenic CSTR: Performance and artificial neural network (ANN) modelling studies

    Energy Technology Data Exchange (ETDEWEB)

    Sahinkaya, Erkan [Harran University, Environmental Engineering Department, Osmanbey Campus, 63000 Sanliurfa (Turkey)], E-mail: erkansahinkaya@yahoo.com

    2009-05-15

    Sulfidogenic treatment of sulfate (2-10 g/L) and zinc (65-677 mg/L) containing simulated wastewater was studied in a mesophilic (35 deg. C) CSTR. Ethanol was supplemented (COD/sulfate = 0.67) as carbon and energy source for sulfate-reducing bacteria (SRB). The robustness of the system was studied by increasing Zn, COD and sulfate loadings. Sulfate removal efficiency, which was 70% at 2 g/L feed sulfate concentration, steadily decreased with increasing feed sulfate concentration and reached 40% at 10 g/L. Over 99% Zn removal was attained due to the formation of zinc-sulfide precipitate. COD removal efficiency at 2 g/L feed sulfate concentration was over 94%, whereas, it steadily decreased due to the accumulation of acetate at higher loadings. Alkalinity produced from acetate oxidation increased wastewater pH remarkably when feed sulfate concentration was 5 g/L or lower. Electron flow from carbon oxidation to sulfate reduction averaged 83 {+-} 13%. The rest of the electrons were most likely coupled with fermentative reactions as the amount of methane production was insignificant. The developed ANN model was very successful as an excellent to reasonable match was obtained between the measured and the predicted concentrations of sulfate (R = 0.998), COD (R = 0.993), acetate (R = 0.976) and zinc (R = 0.827) in the CSTR effluent.

  18. Biotreatment of zinc-containing wastewater in a sulfidogenic CSTR: Performance and artificial neural network (ANN) modelling studies.

    Science.gov (United States)

    Sahinkaya, Erkan

    2009-05-15

    Sulfidogenic treatment of sulfate (2-10g/L) and zinc (65-677mg/L) containing simulated wastewater was studied in a mesophilic (35 degrees C) CSTR. Ethanol was supplemented (COD/sulfate=0.67) as carbon and energy source for sulfate-reducing bacteria (SRB). The robustness of the system was studied by increasing Zn, COD and sulfate loadings. Sulfate removal efficiency, which was 70% at 2g/L feed sulfate concentration, steadily decreased with increasing feed sulfate concentration and reached 40% at 10g/L. Over 99% Zn removal was attained due to the formation of zinc-sulfide precipitate. COD removal efficiency at 2g/L feed sulfate concentration was over 94%, whereas, it steadily decreased due to the accumulation of acetate at higher loadings. Alkalinity produced from acetate oxidation increased wastewater pH remarkably when feed sulfate concentration was 5g/L or lower. Electron flow from carbon oxidation to sulfate reduction averaged 83+/-13%. The rest of the electrons were most likely coupled with fermentative reactions as the amount of methane production was insignificant. The developed ANN model was very successful as an excellent to reasonable match was obtained between the measured and the predicted concentrations of sulfate (R=0.998), COD (R=0.993), acetate (R=0.976) and zinc (R=0.827) in the CSTR effluent.

  19. Experimental investigation of flow pattern and sediment deposition in rectangular shallow reservoirs

    Institute of Scientific and Technical Information of China (English)

    Matthieu DUFRESNE; Benjamin J.DEWALS; Sébastien ERPICUM; Pierre ARCHAMBEAU; Michel PIROTTON

    2010-01-01

    This paper reports the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns were identified (from longer to shorter reservoirs): an asymmetric flow with two reattachment points, an asymmetric flow with one reattachment point, an unstable flow, and a symmetric flow without any reattachment point. Using dye visualizations, the median value and the temporal variability of the reattachment lengths were precisely measured for the asymmetric flows. For each stable flow, sediment tests with plastic particles were carried out. The regions of deposition on the bed of the reservoir were clearly a function of the flow pattern. The transition from an asymmetric flow pattern to a symmetric flow pattern was responsible for an abrupt decrease of the trap efficiency; a number of regression laws were discussed to take it into account.

  20. Enzyme hydrolysis of plasma proteins in a CSTR ultrafiltration reactor: Performances and modeling.

    Science.gov (United States)

    Bressollier, P; Petit, J M; Julien, R

    1988-05-01

    By investigating the effects of four operating variables-volume (V), Ultrafiltration flux (J), enzyme concentration (E), and substrate concentration (S)-on capacity (K) and conversion rate (epsilon) of a hollow fiber CSTR, the performances of the CSTR and the kinetic constants of the reaction were determined. A model which takes into account the course of fractional conversion (X) according to the modified space-time parameter, tau (integrated form of V, J, S, and E), was devised by employing the relationship to integrate the equation for the reaction rate of the CSTR and the expression of the modified space time. Correlation of this model and the experimentally obtained results demonstrates that the characteristics for an ultrafiltration membrane reactor for enzymatic hydrolysis by alcalase of plasma proteins are close to those of an ideal CSTR. Optimal scaling up, however, remains dependent on the compromise which may be obtained between capacity and the conversion rate.

  1. Stochastic Simulation of CSTR-BZ Reaction System%CSTR-BZ复杂化学反应的Monte-Carlo模拟

    Institute of Scientific and Technical Information of China (English)

    魏庆莉; 王贵昌; 蔡遵生; 赵学庄

    2000-01-01

    在Monte-Carlo算法中引入流率项, 通过对具有流率分叉结构的CSTR-BZ反应体系SNB(Showalter-Noyes-Bar-Eli)模型的随机分析, 讨论了最低反应浓度的意义及流率项连续性的影响. 与实验结果及确定性数值积分结果比较表明, 对于流动的实际反应体系, 基于"质量作用定律"的宏观确定性方法仍具有适用性.

  2. Flow Patterns at the Interface Between Free Flow and Sediment Bed

    Science.gov (United States)

    Leonardi, Alessandro; Zanello, Francesca; Pokrajac, Dubravka; Roman, Federico; Armenio, Vincenzo

    2017-04-01

    Bedload transport phenomena in rivers and reservoirs are driven by the flow pattern that develops at the interface between free flow and sediment bed. This is a very difficult area to investigate, due to heterogeneous flow which is often restricted to small length scales and hard to resolve with measuring instruments. Yet its interpretation is of prime interest for the understanding of the mass and momentum exchange between the free flow and the sediment. When dealing with the sediment transport triggering mechanism, most studies focus on the flow that develops above the bed, while the characteristics of the flow inside the bed are usually extrapolated from above or simply neglected. This approach yields an incomplete picture of what happens at the interface. Motivated by this, we propose a study where a free-surface flow tops a permeable bed composed of layers of equally-sized spherical beads. The physics of this configuration, originally analyzed with an experimental setup at the University of Aberdeen, was only partially understood, due to the difficulties in measuring velocity and pressure inside the pores. With a Large-Eddy Simulation (LES) we resolve the velocity and pressure fields in both the free flow and inside the porous bed. The no-slip boundary along the beads' surface is imposed using immersed boundaries, which also allows to compute the force exerted by the flow. We observe the development of momentum exchange between free flow and the porous bed, which activates turbulence penetrations that affect the pores closer to the surface of the permeable bed, and has two important consequences. First, the streamwise velocity in these pores is lower than that in the lower layers, a fact that challenges the usual assumption of a monotonically decreasing velocity profile within the bed. Secondly, the turbulence penetration generates an extra fluctuating component in the sphere lift forces whose role for the initiation of their movement is still not clear.

  3. Flow Patterns and Thermal Drag in a One-Dimensional Inviscid Channel with Heating or Cooling

    Institute of Scientific and Technical Information of China (English)

    1993-01-01

    In this paper investigations on the flow patterns and the thermal drag phenomenon in one -dimensional inviscid channel flow with heating or cooling are described and discussed:expressions of flow rate ratio and thermal drag coefficient for different flow patterns and its physical mechanism are presented.

  4. Oscillatory bromate-oxalic acid-Ce-acetone-sulfuric acid reaction, in CSTR

    OpenAIRE

    Pereira,Janaina A. M.; Roberto B Faria

    2004-01-01

    Periodic oscillations were observed for the first time, in a CSTR, in the system bromate-oxalic acid-Ce(IV)-acetone-sulfuric acid, in a CSTR. A reaction between Ce(IV) and acetone, until now not described in the literature and occurring before the addition of the reagents to the reactor, was identified as a decisive factor for the appearing of the regular oscillations.

  5. Effects of tumors on inhaled pharmacologic drugs: I. Flow patterns.

    Science.gov (United States)

    Martonen, T B; Guan, X

    2001-01-01

    Lung carcinomas are now the most common form of cancer. Clinical data suggest that tumors are found preferentially in upper airways, perhaps specifically at carina within bifurcations. The disease can be treated by aerosolized pharmacologic drugs. To enhance their efficacies site-specific drugs must be deposited selectively. Since inhaled particles are transported by air, flow patterns will naturally affect their trajectories. Therefore, in Part I of a systematic investigation, we focused on tumor-induced effects on airstreams, in Part II (the following article [p. 245]), particle trajectories were determined. To facilitate the targeted delivery of inhaled drugs, we simulated bifurcations with tumors on carinas using a commercial computational fluid dynamics (CFD) software package (FIDAP) with a Cray T90 supercomputer and studied effects of tumor sizes and ventilatory parameters on localized flow patterns. Critical tumor sizes existed; e.g., tumors had dominant effects when r/R > or = 0.8 for bifurcation 3-4 and r/R > or = 0.6 for bifurcation 7-8 (r = tumor radius and R = airway radius). The findings suggest that computer modeling is a means to integrate alterations to airway structures caused by diseases into aerosol therapy protocols.

  6. Mathematical Modeling of Electrolyte Flow Dynamic Patterns and Volumetric Flow Penetrations in the Flow Channel over Porous Electrode Layered System in Vanadium Flow Battery with Serpentine Flow Field Design

    CERN Document Server

    Ke, Xinyou; Alexander, J Iwan D; Savinell, Robert F

    2016-01-01

    In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in the flow channel over the porous electrode layered system in vanadium flow battery with serpentine flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic flow inlet boundary conditions. However, the volumetric flow penetration within the porous electrode beneath the flow channel through the integration of interface flow velocity reveals that this value is identical under both ideal plug flow and ideal parabolic flow inlet boundary conditions. The volumetric flow penetrations under the advection effects of flow channel and landing/rib are estimated. The maximum current density achieved in the flow battery can be predicted based on the 100% amount of electrolyte flow reactant ...

  7. FLOW PATTERN AND PRESSURE LOSS OF OIL-WATER TWO-PHASE FLOW IN HORIZONTAL STEEL PIPE

    Institute of Scientific and Technical Information of China (English)

    CHEN Jie; YAN Da-fan; ZHAO Jing-mei; AN Wei-jie; YAN Da-chun

    2005-01-01

    Experimental Study on oil-water two-phase flow patterns and pressure loss was conducted on a horizontal steel pipe loop with 26.1mm inner diameter and 30m total length.The working fluids are white oil, diesel oil and tap water.Several instruments, including a new type of liquid-probe are successfully integrated to identify 7 different flow patterns.The characteristics of the flow patterns and the transition process were observed and depicted in this paper.Investigation revealed that the pressure loss was mainly depended on the flow patterns.

  8. Decoding complex flow-field patterns in visual working memory.

    Science.gov (United States)

    Christophel, Thomas B; Haynes, John-Dylan

    2014-05-01

    There has been a long history of research on visual working memory. Whereas early studies have focused on the role of lateral prefrontal cortex in the storage of sensory information, this has been challenged by research in humans that has directly assessed the encoding of perceptual contents, pointing towards a role of visual and parietal regions during storage. In a previous study we used pattern classification to investigate the storage of complex visual color patterns across delay periods. This revealed coding of such contents in early visual and parietal brain regions. Here we aim to investigate whether the involvement of visual and parietal cortex is also observable for other types of complex, visuo-spatial pattern stimuli. Specifically, we used a combination of fMRI and multivariate classification to investigate the retention of complex flow-field stimuli defined by the spatial patterning of motion trajectories of random dots. Subjects were trained to memorize the precise spatial layout of these stimuli and to retain this information during an extended delay. We used a multivariate decoding approach to identify brain regions where spatial patterns of activity encoded the memorized stimuli. Content-specific memory signals were observable in motion sensitive visual area MT+ and in posterior parietal cortex that might encode spatial information in a modality independent manner. Interestingly, we also found information about the memorized visual stimulus in somatosensory cortex, suggesting a potential crossmodal contribution to memory. Our findings thus indicate that working memory storage of visual percepts might be distributed across unimodal, multimodal and even crossmodal brain regions. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. THE FLOW PATTERNS OF BUBBLE PLUME IN AN MBBR

    Institute of Scientific and Technical Information of China (English)

    LI Shi-rong; CHENG Wen; WANG Meng; CHEN Chen

    2011-01-01

    The flow patterns of the gas-liquid two-phase flow in a Moving-Bed Biofilm Reactor(MBBR)have a critical effect upon the mass transfer by the convection.Bubble plumes promote unsteadily fluctuating two-phase flows during the aeration.This article studies the unsteady structure of bubble plumes through experiments.The time-serial bubble plume images in various cases of the tank are analyzed.The Recursive Cross Correlation-Particle Image Velocimetry(RCC-PIV)is used to calculate the velocities in those cases,and then the time-serial vortex,the total turbulence intensity,the time-serial streamline are obtained.It is shown that the aspect ratio and the void fraction are the dominant factors influencing the unsteady structure of bubble plumes.When the aspect ratio is unity and the void fraction is high,the bubble plumes see a symmetrical vortex structure with a long residence time,which is beneficial for optimizing the aeration system and enhancing the applied range of bubble plumes.

  10. Characterization of the flow pattern of a gas/solids flow in a downer reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lehner, P.; Wirth, K.E. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Mechanische Verfahrenstechnik

    1999-07-01

    The downer reactor is discussed in literature as a new type of gas/solids reactor. Due to the cocurrent movement of gas and solids in direction of gravity, it is expected that a narrow residence time distribution and a flow regime close to plug flow can be established in this reactor. Recent studies show, that the gas/solids distributor on the top of the downer mainly influences the flow conditions. However, the influence of the physical properties of the solids and the plant setup on the flow behavior is still ambiguous. Therefore, experimental investigations concerning the local and cross-sectional solids distribution have been carried out under different operating conditions (variation of superficial gas velocity and solids circulation rate) and with different solids (glass beads, d{sub p}=60 {mu}m and d{sub p}=130 {mu}m). An X-ray computed tomography system has been used to obtain the solids concentration distribution in the entire cross-section at different axial positions of the downer. Pressure profiles can provide additional information about the overall behavior of the gas/solids flow. Results show a significant influence of the entrance conditions of the gas/solids flow on the flow pattern in the region below the gas/solids distributor. After a significant length, depending on solids properties and superficial gas velocity, similar flow behavior can be noticed for different entrance conditions. Superficial gas velocity not only influences the entrance length, but also the solids distribution in the entire cross-section of the downer. (orig.)

  11. A Comparative Study on Temperature Control of CSTR using PI Controller, PID Controller and PID (Two Degree of Freedom) Controller

    OpenAIRE

    Bikash Dey; Lusika Roy

    2014-01-01

    This paper present three different control strategies based on PI Control, PID control and Two degree of freedom PID control for Continuous Stirred Tank Reactor (CSTR).CSTR which offers a diverse range of application in the field of chemical engineering as well as in the control engineering and is an attractive research area for process control researchers. Our objective is to control the temperature of CSTR in presence of the set point. MATLAB SIMULINK software is used for mo...

  12. Simulation of Flow Pattern around Inclined Bridge Group Pier using FLOW-3D Software

    Directory of Open Access Journals (Sweden)

    Malihesadat Jafari

    2017-03-01

    Full Text Available Introduction: Bridges are certainly one of the most important structures but costly service elements in a transport system. The bridges are very required to access the damaged areas in emergency situations such as floods and earthquakes. Scour around the foundations of bridge piers exposed to the flowing water than can destroy the bridge itself is a subject of major concern. Flow pattern is known as responsible for all changes in stream bed. Any obstacle in the channel can form new flow patterns causing additional shear stress exerted on the bed than the equilibrium condition of the absence of the obstacle. Appropriate shaping of flow pattern and proper selecting of pier geometry and the location of bridge piers can be one of the proper methods in reduction of scour amount which is the main subject of the present study. Materials and Methods: Inclined bridge group pier is a type of bridges with modern geometry based on development in building technology of structures. Many of these bridges have been built all around the world and the 8th bridge built crossing the Karun River in Ahvaz is a sample of the Iranian ones considered in this research. Hydrodynamic behavior of flow is investigated around the inclined bridge group pier settled on foundation using the FLOW-3D numerical model. Inclined bridge group pier investigated in this study, includes two rectangular piers which are 2.5 cm long and 3.5 cm wide and set in an angle of 28 degree on rectangular foundation which is 16 cm long and 10 cm wide and installed in three different foundation levels namely at, above and below the bed levels. The physical model of prototype pier considered in this study was constructed to the scale of 1:190 of the Ahvaz 8th bridge. In order to verify the accuracy of the numerical model, velocity data obtained from image processing technique were used. Results and Discussion: Due to non- linearity and interactions between various phenomena involved, flow pattern

  13. NUMERICAL INVESTIGATION OF FLOW PATTERNS IN DIFFERENT PUMP INTAKE SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    ZHAN Jie-min; WANG Ben-cheng; YU Ling-hui; LI Yok-sheung; TANG Ling

    2012-01-01

    A 3-D numerical model for pump intake is established based on the Navier-Stokes equations with the RNG k-εturbulence model and the VOF method to simulate the free surface.The applicability of the proposed model is validated by a test case of non-symmetric pump-intake bay.The predicted locations,structures and shapes of all vortices are in good agreement with those observed in experiments,though with some differences in vorticity strengths.The flow pattern and the efficiency of five types of pump intake systems are studied.The discharge and the velocity uniformity of the intake system are used as indices to evaluate its performance.

  14. Effect of post-digestion temperature on serial CSTR biogas reactor performance.

    Science.gov (United States)

    Boe, Kanokwan; Karakashev, Dimitar; Trably, Eric; Angelidaki, Irini

    2009-02-01

    The effect of post-digestion temperature on a lab-scale serial continuous-flow stirred tank reactor (CSTR) system performance was investigated. The system consisted of a main reactor operated at 55 degrees C with hydraulic retention time (HRT) of 15 days followed by post-digestion reactors with HRT of 5.3 days. Three post-digestion temperatures (55 degrees C, 37 degrees C and 15 degrees C) were compared in terms of biogas production, process stability, microbial community and methanogenic activity. The results showed that the post-digesters operated at 55 degrees C, 37 degrees C and 15 degrees C gave extra biogas production of 11.7%, 8.4% and 1.2%, respectively. The post-digester operated at 55 degrees C had the highest biogas production and was the most stable in terms of low VFA concentrations. The specific methanogenic activity tests revealed that the main reactor and the post-digester operated at 55 degrees C and 37 degrees C had very active acidogens and methanogens. In contrast, very low methanogenic activity was observed at 15 degrees C.

  15. Anaerobic treatment of Tequila vinasses in a CSTR-type digester.

    Science.gov (United States)

    Méndez-Acosta, Hugo Oscar; Snell-Castro, Raúl; Alcaraz-González, Víctor; González-Alvarez, Víctor; Pelayo-Ortiz, Carlos

    2010-06-01

    Tequila industries in general produce great volumes of effluents with high pollutant loads, which are discharged (untreated or partially treated) into natural receivers, thus causing severe environmental problems. In this contribution, we propose an integrated system as a first step to comply with the Mexican ecological norms and stabilize the anaerobic treatment of Tequila vinasses with main design criteria: simple and easy operation, reduce operating time and associated costs (maintenance), integrated and compact design, minimal cost of set-up, start-up, monitoring and control. This system is composed of a fully instrumented and automated lab-scale CSTR-type digester, on-line measuring devices of key variables (pH, temperature, flow rates, etc.), which are used along with off-line readings of chemical oxygen demand (COD), biogas composition, alkalinity and volatile fatty acids to guarantee the operational stability of the anaerobic digestion process. The system performance was evaluated for 200 days and the experimental results show that even under the influence of load disturbances, it is possible to reduce the COD concentration to 85% in the start-up phase and up to 95% during the normal operation phase while producing a biogas with a methane composition greater than 65%. It is also shown that in order to maintain an efficient treatment, the buffering capacity (given by the alkalinity ratio, alpha = intermediate alkalinity/total alkalinity) must be closely monitored.

  16. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows

    OpenAIRE

    Yatou, Hiroki

    2010-01-01

    We find three types of steady solutions and remarkable flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Reynolds (Re) and Weissenberg (Wi) numbers using direct numerical simulations with spectral element method. The solutions are called "convective", "transition", and "elastic" in ascending order of Wi. In the convective region in the Re-Wi parameter space, the convective effect and the pressure gradient balance on average. As Wi increases, th...

  17. BASIC FLOW PATTERNS AND OPTIMUM HYDRAULIC DESIGN OF A SUCTION BOX OF PUMPING STATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A numerical method based on 3-D turbulence flow was applied to simulate the flow pattern in suction boxes of six different types.In light of the computational results, the basic flow patterns in the boxes were revealed and a theoretical method to optimize hydraulically design of the suction box is developed.The box geometrical parameters, which influence the flow pattern in the box, could be optimized.The optimum criteria for the hydraulic design of the suction boxes of six types established, respectively.Furthermore, a summarization is given here based on the classification of the basic flow patterns in order to systematically understand the hydraulic design of suction boxes.

  18. SIMULATION AND ANALYSIS OF FLOW PATTERN IN CROSS-CORRUGATED PLATE HEAT EXCHANGERS

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guan-min; TIAN Mao-cheng; ZHOU Shou-jun

    2006-01-01

    Using numerical methodology, the flow fields between two corrugated plates with different values of the corrugation inclination angle β were simulated.The simulation results directly indicate that β affects the flow pattern between corrugated plates, and the results are in good agreement with the experimental results reported by interrelated literature.The results show that the flow pattern between the two plates changes from "double cross-flow" to "zigzag flow" with the increase in β.The reason for the effect on the flow pattern between the two corrugated plates was discussed from the view of the variation of momentum in the direction of corrugation with the variation in β.

  19. Plastic flow pattern and its effect in friction stir welding of A2024 and A1060

    Institute of Scientific and Technical Information of China (English)

    WANG Xi-jing; ZHANG Zhong-ke; LI Jing; DA Chao-bing

    2006-01-01

    During the friction stir welding (FSW), the property of the welding joint is highly affected by the plastic and viscous flow behavior of the softened material. The flow pattern of the welded material was examined through observing the microstructural distribution of friction stir welded joints between dissimilar 2024 and 1060 aluminum alloy. The experimental results show that the flow patterns of material at different locations in the weld are different and can be divided into four layers along the thickness direction: surface flow layer influenced by the shoulder of the tool, in which the material tends to flow as integrity; horizontal flow layer influenced by the surface flow layer, in which the material of surface flow layer enters and flows forwards under the advancing force of the tool; vertical flow layer (plastic flow area induced by stirring of the pin), in which the flow pattern is complex and onion rings can often be observed; unstirred bottom layer because of the length of the pin being shorter than the thickness of the plates. The effect of plastic flow on welding quality was further investigated. The study suggests that welding quantity is significantly influenced by the flow pattern and defects always appear in horizontally lamellar flow region because of the complex flow pattern.

  20. Factors Influencing the Disturbed Flow Patterns Downstream of Curved Atherosclerotic Arteries

    Institute of Scientific and Technical Information of China (English)

    Biyue Liu

    2008-01-01

    Pulsatile blood flows in curved atherosclerotic arteries are studied by com-puter simulations. Computations are carried out with various values of physiological parameters to examine the effects of flow parameters on the disturbed flow patterns downstream of a curved artery with a stenosis at the inner wall. The numerical re-sults indicate a strong dependence of flow pattern on the blood viscosity and inlet flow rate, while the influence of the inlet flow profile to the flow pattem in downstream is negligible.

  1. Dynamic thermal-hydraulic modeling and stack flow pattern analysis for all-vanadium redox flow battery

    Science.gov (United States)

    Wei, Zhongbao; Zhao, Jiyun; Skyllas-Kazacos, Maria; Xiong, Binyu

    2014-08-01

    The present study focuses on dynamic thermal-hydraulic modeling for the all-vanadium flow battery and investigations on the impact of stack flow patterns on battery performance. The inhomogeneity of flow rate distribution and reversible entropic heat are included in the thermal-hydraulic model. The electrolyte temperature in tanks is modeled with the finite element modeling (FEM) technique considering the possible non-uniform distribution of electrolyte temperature. Results show that the established model predicts electrolyte temperature accurately under various ambient temperatures and current densities. Significant temperature gradients exist in the battery system at extremely low flow rates, while the electrolyte temperature tends to be the same in different components under relatively high flow rates. Three stack flow patterns including flow without distribution channels and two cases of flow with distribution channels are compared to investigate their effects on battery performance. It is found that the flow rates are not uniformly distributed in cells especially when the stack is not well designed, while adding distribution channels alleviates the inhomogeneous phenomenon. By comparing the three flow patterns, it is found that the serpentine-parallel pattern is preferable and effectively controls the uniformity of flow rates, pressure drop and electrolyte temperature all at expected levels.

  2. Copepod feeding currents : flow patterns, filtration rates and energetics

    NARCIS (Netherlands)

    van Duren, LA; Stamhuis, EJ; Videler, JJ

    2003-01-01

    Particle image velocimetry was used to construct a quasi 3-dimensional image of the flow generated by the feeding appendages of the calanoid copepod Temora longicornis. By scanning layers of flow, detailed information was obtained on flow velocity and velocity gradients. The flow around feeding T. l

  3. Zonal Flow Patterns: How Toroidal Coupling Induces Phase Jumps and Shear Layers

    CERN Document Server

    Guo, Z B

    2016-01-01

    A new, frequency modulation mechanism for zonal flow pattern formation is presented. The model predicts the probability distribution function of the flow strength as well as the evolution of the characteristic spatial scale. Magnetic toroidicity-induced global phase dynamics is shown to determine the spatial structure of the flow. A key result is the observation that global phase patterning can lead to zonal flow formation in the absence of turbulence inhomogeneity.

  4. Dissolution patterns and mixing dynamics in unstable reactive flow

    Science.gov (United States)

    Hidalgo, Juan J.; Dentz, Marco; Cabeza, Yoar; Carrera, Jesus

    2015-08-01

    We study the fundamental problem of mixing and chemical reactions under a Rayleigh-Taylor-type hydrodynamic instability in a miscible two-fluid system. The dense fluid mixture, which is generated at the fluid-fluid interface, leads to the onset of a convective fingering instability and triggers a fast chemical dissolution reaction. Contrary to intuition, the dissolution pattern does not map out the finger geometry. Instead, it displays a dome-like, hierarchical structure that follows the path of the ascending fluid interface and the regions of maximum mixing. These mixing and reaction hot spots coincide with the flow stagnation points, at which the interfacial mixing layer is compressed and deformed. We show that the deformation of the boundary layer around the stagnation points controls the evolution of the global scalar dissipation and reaction rates and shapes the structure of the reacted zones. The persistent compression of the mixing layer explains the independence of the mixing rate from the Rayleigh number when convection dominates.

  5. SCOUR DEPTH AND FLOW PATTERN OF ERODING PLANE JETS

    Institute of Scientific and Technical Information of China (English)

    A.KURNIAWAN; M.S.ALTINAKAR; W.H.GRAF

    2004-01-01

    Local scour may occur when a hydraulic structure is positioned in a channel with an erodible bed.Herewith investigated experimentally are the erosion and flow pattern due to a water jet passing over a channel bed at the asymptotic (final) state. The development of the scour hole, its maximum scour depth and length, are recorded and compared with available scour-depth relations. Two sets of experiments (see Table 1) were carried out. Set 1 (3 runs) was concerned with measuring the vertical instantaneous velocity distribution in the scour hole. The scour hole at the asymptotic (final) state, t ≈100 [h] was investigated. Set 2 (5 runs) was concerned with studying the physics of scouring. The scour hole at about mid-state, t ≈ 0.5 [h], was investigated; subsequently the scour-hole depth was linearly extended on the semi-log scale to 72 [h]; no velocity measurements were performed. The present data are put in context with some (popular) existing relations; recommended is a modification of some of these relations.

  6. Patterns in groundwater chemistry resulting from groundwater flow

    Science.gov (United States)

    Stuyfzand, Pieter J.

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic-methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500m in the flow direction is shown to correspond with about 5000yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Résumé Les écoulements souterrains influencent les différents types hydrochimiques, parce que l'écoulement réduit le mélange par diffusion, porte les marques chimiques de changements biologiques et anthropiques dans la zone d'alimentation et lessive le système aquifère. Ces types dans leur ensemble sont surtout déterminés par des différences dans le flux d'eau météorique traversant le sous-sol. Dans les "hydrosomes" (masses d'eau d'origine déterminée), les lignes marquant une évolution prograde (séquence de faciès) se développent normalement dans la direction de l'écoulement souterrain : depuis des fluctuations fortes de la

  7. Detection of Two-Phase Flow Patterns in a Vertical Minichannel Using the Recurrence Quantification Analysis

    Directory of Open Access Journals (Sweden)

    Mosdorf Romuald

    2015-06-01

    Full Text Available The two-phase flow (water-air occurring in square minichannel (3x3 mm has been analysed. In the minichannel it has been observed: bubbly flow, flow of confined bubbles, flow of elongated bubbles, slug flow and semi-annular flow. The time series recorded by laser-phototransistor sensor was analysed using the recurrence quantification analysis. The two coefficients:Recurrence rate (RR and Determinism (DET have been used for identification of differences between the dynamics of two-phase flow patterns. The algorithm which has been used normalizes the analysed time series before calculating the recurrence plots.Therefore in analysis the quantitative signal characteristicswas neglected. Despite of the neglect of quantitative signal characteristics the analysis of its dynamics (chart of DET vs. RR allows to identify the two-phase flow patterns. This confirms that this type of analysis can be used to identify the two-phase flow patterns in minichannels.

  8. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows

    CERN Document Server

    Yatou, Hiroki

    2010-01-01

    We find three types of steady solutions and remarkable flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Reynolds (Re) and Weissenberg (Wi) numbers using direct numerical simulations with spectral element method. The solutions are called "convective", "transition", and "elastic" in ascending order of Wi. In the convective region in the Re-Wi parameter space, the convective effect and the pressure gradient balance on average. As Wi increases, the elastic effect becomes suddenly comparable and the first transition sets in. Through the transition, a separation vortex disappears and a jet flow induced close to the wall by the viscoelasticity moves into the bulk; The viscous drag significantly drops and the elastic wall friction rises sharply. This transition is caused by an elastic force in the streamwise direction due to the competition of the convective and elastic effects. In the transition region, the convective and elastic effects balance. When the elastic eff...

  9. [Study on immobilized cells for producing alpha-amylase by using polyving alcohol as the carrier(II): The effect of fermentating conditions on the ability producing alpha-amylase of the cells immobilized with polyving alcohol as the corrier and continuous fermentation of the immobilized cells in CSTR].

    Science.gov (United States)

    Liu, Z; Wang, J; Li, Z

    1998-03-01

    The effects of fermentating conditions on the ability of immobilized cells with PVA as carrier for producing alpha-amylase were studied. The continuous fermentation with the immobilized cells were tested in continuous flow stirred tank reactor (CSTR). The results showed that the adaptability of the immobilized Bacillus substilis to pH increased after immobilization. In CSTR, the immobilized cells can be fermentated continuously for 360 hrs and the activity of alpha-amylase can be kept on the level of about 170 u/ml.

  10. A study on effects of cash flow patterns and auditors’ opinions in predicting financial distress

    Directory of Open Access Journals (Sweden)

    Fatemeh Namvar

    2013-07-01

    Full Text Available Bankruptcy has been one of the most important issues among investors in stock market and there are literally different techniques for predicting bankruptcy. In this paper, we study on effects of cash flow patterns and auditors’ opinions in predicting financial distress on some 80 selected firms traded on Tehran Stock Exchange over the period 2005-2011. In this study, the combination of cash flow patterns represent firm’s resource allocations and operational capabilities interacted with their strategy choices. In additions, predictions about each individual cash flow components, operational, investment, financial, are derived from economic theory, which forms a basis for the life proxy. We use cash flow patterns in the decline stage and compare the results with auditors’ opinions. The results indicate that cash flow patterns could predict financial distress companies in Iran. In addition, the effective cash flow patterns in predicting financial distress is more than auditors’ feedbacks.

  11. Numerical Study of Flow Motion and Patterns Driven by a Rotating Permanent Helical Magnetic Field

    Science.gov (United States)

    Yang, Wenzhi; Wang, Xiaodong; Wang, Bo; Baltaretu, Florin; Etay, Jacqueline; Fautrelle, Yves

    2016-10-01

    Liquid metal magnetohydrodynamic flow driven by a rotating permanent helical magnetic field in a cylindrical container is numerically studied. A three-dimensional numerical simulation provides insight into the visualization of the physical fields, including the magnetic field, the Lorentz force density, and the flow structures, especially the flow patterns in the meridional plane. Because the screen parameter is sufficiently small, the model is decoupled into electromagnetic and hydrodynamic components. Two flow patterns in the meridional plane, i.e., the global flow and the secondary flow, are discovered and the impact of several system parameters on their transition is investigated. Finally, a verifying model is used for comparison with the previous experiment.

  12. The Effect of Sudden Change in Pipe Diameter on Flow Patterns of Air-Water Two-Phase

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Flow patterns upstream and downstream of a sudden-contraction cross-section in a vertical straight pipe were presented. By comparing with flow patterns in uniform croes-section vertical tubes, the effect of the sudden change in pipe diameter on flow patterns was analyzed. Flow pattern transition mechanisms were discussed and transition criteria for flow pattern transitions were deduced accordingly using the dimensional analysis.

  13. EFFECT OF SURFACTANT ON TWO-PHASE FLOW PATTERNS OF WATER-GAS IN CAPILLARY TUBES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1.60 mm. The working liquid was the mixture of water and Sodium Dodecyl Benzoyl Sulfate (SDBS). The working gas was Nitrogen. For the water/SDBS mixture-gas flow in the vertical capillary tube, flow-pattern transitions occurred at lower flow velocities than those for the water-gas flow in the same tube. For the water/SDBS mixture-gas flow in the horizontal capillary tube, surface tension had little effect on the bubbly-intermittent transition and had only slight effect on the plug-slug and slug-annular transitions. However, surface tension had significant effect on the wavy stratified flow regime. The wavy stratified flow regime of water/SDBS mixture-gas flow expanded compared with that of water-gas.

  14. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows.

    Science.gov (United States)

    Yatou, Hiroki

    2010-09-01

    We numerically find three types of steady solutions of viscoelastic flows and flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Weissenberg (Wi) and Reynolds (Re) numbers using a spectral element method. The solutions are called "convective," "transition," and "elastic" in ascending order of Wi. In the convective region in the Wi-Re parameter space, convective effect and pressure gradient balance on average. As Wi increases, elastic effect becomes comparable, and the first transition sets in. Through the transition, a separation vortex disappears, and a jet flow induced close to the wall by the viscoelasticity moves into the bulk; the viscous drag significantly drops, and the elastic wall friction rises sharply. This transition is caused by an elastic force in the streamwise direction due to the competition of the convective and elastic effects. In the transition region, the convective and elastic effects balance. When the elastic effect becomes greater than the convective effect, the second transition occurs but it is relatively moderate. The second transition seems to be governed by the so-called Weissenberg effect. These transitions are not sensitive to driving forces. By a scaling analysis, it is shown that the stress component is proportional to the Reynolds number on the boundary of the first transition in the Wi-Re space. This scaling coincides well with the numerical result.

  15. Regional patterns of cortical blood flow distinguish extraverts from introverts

    OpenAIRE

    Stenberg, Georg; Risberg, Jarl; Warkentin, S.; Rosén, Ingmar

    1990-01-01

    Eysenck's hypothesis of higher cortical arousal in introverts was examined using regional cerebral blood flow measurement in 37 healthy subjects . The measurement was made at rest, using the133Xe-inhalation method. Estimates of gray matter flow were obtained for 32 brain regions. There was no significant evidence of personality differences in general arousal, as measured by the mean flow level, averaged over all regions. There were, however, regional differences. An overall test of the blood ...

  16. OPTIMIZATION OF COAL PARTICLE FLOW PATTERNS IN LOW NOX BURNERS

    Energy Technology Data Exchange (ETDEWEB)

    Jost O.L. Wendt; Gregory E. Ogden; Jennifer Sinclair; Caner Yurteri

    2001-08-20

    The proposed research is directed at evaluating the effect of flame aerodynamics on NO{sub x} emissions from coal fired burners in a systematic manner. This fundamental research includes both experimental and modeling efforts being performed at the University of Arizona in collaboration with Purdue University. The objective of this effort is to develop rational design tools for optimizing low NO{sub x} burners to the kinetic emissions limit (below 0.2 lb./MMBTU). Experimental studies include both cold and hot flow evaluations of the following parameters: flame holder geometry, secondary air swirl, primary and secondary inlet air velocity, coal concentration in the primary air and coal particle size distribution. Hot flow experiments will also evaluate the effect of wall temperature on burner performance. Cold flow studies will be conducted with surrogate particles as well as pulverized coal. The cold flow furnace will be similar in size and geometry to the hot-flow furnace but will be designed to use a laser Doppler velocimeter/phase Doppler particle size analyzer. The results of these studies will be used to predict particle trajectories in the hot-flow furnace as well as to estimate the effect of flame holder geometry on furnace flow field. The hot-flow experiments will be conducted in a novel near-flame down-flow pulverized coal furnace. The furnace will be equipped with externally heated walls. Both reactors will be sized to minimize wall effects on particle flow fields. The cold-flow results will be compared with Fluent computation fluid dynamics model predictions and correlated with the hot-flow results with the overall goal of providing insight for novel low NO{sub x} burner geometry's.

  17. Polynomial analysis of placental flow patterns in growth-retarded fetuses.

    Science.gov (United States)

    Hütter, W; Grab, D; Sterzik, K; Terinde, R; Wolf, A

    1993-01-01

    Correct interpretation of conspicuous blood flow velocity waveforms cannot rely solely on the evaluation of uteroplacental vascular Doppler flow patterns by means of angle-independent indices such as the resistance or pulsatility index. In addition to the degree of pulsatility, the waveform shape between the systolic and diastolic peak values is of considerable consequence. A subdivision of the total flow waveform into orthogonal polynomial components allows both pulsatility evaluation and notching to be registered, providing a higher sensitivity in identification of pathological vascular resistance. Accurate recording and assessment of the flow waveform is therefore an important qualitative criterion for the classification of Doppler flow patterns in pregnancies with reduced uteroplacental perfusion.

  18. Longitudinal cerebral blood flow and amyloid deposition: an emerging pattern?

    Science.gov (United States)

    Sojkova, Jitka; Beason-Held, Lori; Zhou, Yun; An, Yang; Kraut, Michael A; Ye, Weigo; Ferrucci, Luigi; Mathis, Chester A; Klunk, William E; Wong, Dean F; Resnick, Susan M

    2008-01-01

    Although cerebral amyloid deposition may precede cognitive impairment by decades, the relationship between amyloid deposition and longitudinal change in neuronal function has not been studied. The aim of this paper is to determine whether nondemented individuals with high and low amyloid burden show different patterns of longitudinal regional cerebral blood flow (rCBF) changes in the years preceding measurement of amyloid deposition. Methods Twenty-eight nondemented participants (mean (SD) age at [11C] PIB 82.5(4.8) yrs; 6 mildly impaired) from the Baltimore Longitudinal Study of Aging underwent yearly resting-state [15O]H2O PET scans for up to 8 years. [11C]PIB images of amyloid deposition were acquired on average 10.8(0.8) years after the first CBF scan. [11C]PIB distribution volume ratios (DVR) of regions of interest were estimated by fitting a reference tissue model to the measured time activity curves. Based on mean cortical DVR, participants were divided into high and low [11C]PIB retention groups. Differences in longitudinal rCBF changes between high and low [11C]PIB groups were investigated by voxel-based analysis. Results Longitudinal rCBF changes differed significantly between high (n=10) and low (n=18) [11C]PIB groups (p<=0.001). Greater longitudinal decreases in rCBF in the high [11C]PIB group were seen in right anterior/mid cingulate, right supramarginal gyrus, left thalamus and midbrain bilaterally relative to the low group. Greater increases in rCBF over time in the high [11C]PIB group were found in left medial and inferior frontal gyri, right precuneus, left inferior parietal lobule, and the left postcentral gyrus. Conclusion In this group of nondemented older adults, those with high [11C]PIB show greater longitudinal declines in rCBF in certain areas, representing regions with greater decrements in neuronal function. Greater longitudinal increases in rCBF are also observed in those with higher amyloid load and may represent an attempt to preserve

  19. Study of Wettability Effect on Pressure Drop and Flow Pattern of Two-Phase Flow in Rectangular Microchannel

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Chi Woong; Yu, Dong In; Kim, Moo Hwan [Pohang University of Science and Technology, Pohang (Korea, Republic of)

    2009-12-15

    Wettability is a critical parameter in micro-scale two-phase system. Several previous results indicate that wettability has influential affect on two-phase flow pattern in a microchannel. However, previous studies conducted using circular microtube, which was made by conventional fabrication techniques. Although most applications for micro thermal hydraulic system has used a rectangular microchannel, data for the rectangular microchannel is totally lack. In this study, a hydrophilic rectangular microchannel was fabricated using a photosensitive glass. And a hydrophobic rectangular microchannel was prepared using silanization of glass surfaces with OTS (octa-dethy1-trichloro-siliane). Experiments of two-phase flow in the hydrophilic and the hydrophobic rectangular microchannels were conducted using water and nitrogen gas. Visualization of two-phase flow pattern was carried out using a high-speed camera and a long distance microscope. Visualization results show that the wettability was important for two-phase flow pattern in rectangular microchannel. In addition, two-phase frictional pressure drop was highly related with flow patterns. Finally, Two-phase frictional pressure drop was analyzed with flow patterns.

  20. Patterns of the turbulent Taylor-Couette flow

    Science.gov (United States)

    Prigent, Arnaud; Talioua, Abdessamad; Mutabazi, Innocent

    2016-11-01

    We are interested in the study of the transition to turbulence in the Taylor-Couette flow, the flow between two independently rotating coaxial cylinders. Once the geometry is fixed, the flow is controlled by the inner and outer Reynolds numbers and present a large variety of flow regimes. In counter-rotation, the transition is characterized by a succession of more or less turbulent flow regimes: intermittency with turbulent spots, spiral turbulence, featureless turbulence. For larger values of the inner Reynolds number, turbulent Taylor roll re-emerge from the featureless turbulence and remain for very large values of the Reynolds numbers. Bifurcations between different turbulent rolls states are even observed in the ultimate turbulence regime. Nevertheless the transition from the featureless turbulence to the turbulent rolls still requires a detailed study and the mechanism which causes and sustains turbulent spots or turbulent spirals remains unknown. In this study we present new experimental information on the organization of the flow for the different regimes with turbulence. The experiments are conducted in a Taylor-Couette flow with η = 0 . 8 . Stereo-Particle Image Velocimetry measurements and visualizations of the different flow regimes are realized and discussed. This work was supported by the ANR TRANSFLOW - ANR-13-BS09-0025.

  1. Array of Biomimetic Hair Sensor Dedicated for Flow Pattern Recognition

    NARCIS (Netherlands)

    Dagamseh, A.M.K.; Bruinink, C.M.; Kolster, Marcel; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.

    Flow sensor arrays can be used to extract features from flow fields rather than averaging or providing local measurements provided the sensors in the array structure can be interrogated individually. This paper addresses the latest developments in fabrication and array interfacing of biomimetic

  2. Two-stage anaerobic fermentation of organic waste in CSTR and UFAF-reactors.

    Science.gov (United States)

    Held, Christof; Wellacher, Martin; Robra, Karl-Heinz; Gübitz, Georg M

    2002-01-01

    The mechanically separated liquid fraction of organic waste from households was used as a substrate for anaerobic fermentation. A two-step system consisting of a 2001 continuously stirred tank reactor (CSTR) and a 501 upflow anaerobic filter filled with glass foam pearls was constructed. The CSTR was operated for 5 months with a loading rate of 9.8 kg CSB m(-3) day(-1). At a resulting hydraulic retention time (HRT) of 24 days, 68% COD was degraded and a gas productivity of 4.0 m3 m(-3) day(-1) was achieved. Further digestion of the CSTR output was separately optimised in a 20 l-UFAF and based on these results a 50 l-UFAF was connected to the CSTR. At a resulting hydraulic retention time (HRT) of 6 days 38% COD was degraded and a gas productivity of 1.8 m3 m(-3) day(-1) was achieved with the 50 l-UFAF. Thus, the overall degradation efficiency of the two-phase system was 80%. The methane content (61%) of the biogas produced in the 50 l-UF

  3. From Brayton-Moser formulation to Port Hamiltonian representation : the CSTR case study.

    OpenAIRE

    Hoang, N.H.; Couenne, Françoise; Dochain, Denis; Le Gorrec, Yann

    2011-01-01

    International audience; This paper shows that any thermodynamic variable ful lling some stability criterion can be used as Hamiltonian for pseudo hamiltonian representation of a non isothermal Continuous Stirred Tank Reactor (CSTR) model. More precisely it is shown that from Brayton- Moser formulation is obtained some port hamiltonian representation with negative dissipation. This result is shown for reaction A !B.

  4. Profound spatial heterogeneity of coronary reserve. Discordance between patterns of resting and maximal myocardial blood flow.

    Science.gov (United States)

    Austin, R E; Aldea, G S; Coggins, D L; Flynn, A E; Hoffman, J I

    1990-08-01

    We examined the ability of individual regions of the canine left ventricle to increase blood flow relative to baseline rates of perfusion. Regional coronary flow was measured by injecting radioactive microspheres over 90 seconds in seven anesthetized mongrel dogs. Preliminary experiments demonstrated a correlation between the regional distributions of blood flow during asphyxia and pharmacological vasodilatation with adenosine (mean r = 0.75; 192 regions in each of two dogs), both of which resulted in increased coronary flow. Subsequent experiments, during which coronary perfusion pressure was held constant at 80 mm Hg, examined the pattern of blood flow in 384 regions (mean weight, 106 mg) of the left ventricular free wall during resting flow and during maximal coronary flow effected by intracoronary adenosine infusion. We found that resting and maximal flow patterns were completely uncorrelated to each other in a given dog (mean r = 0.06, p = NS; n = 3 dogs). Furthermore, regional coronary reserve, defined as the ratio of maximal to resting flow, ranged from 1.75 (i.e., resting flow was 57% of maximum) to 21.9 (resting flow was 4.5% of maximum). Thus, coronary reserve is spatially heterogeneous and determined by two distinct perfusion patterns: the resting (control) pattern and the maximal perfusion pattern. Normal hearts, therefore, contain small regions that may be relatively more vulnerable to ischemia. This may explain the patchy nature of infarction with hypoxia and at reduced perfusion pressures as well as the difficulty of using global parameters to predict regional ischemia. Despite the wide dispersion of coronary reserve, we found, by autocorrelation analysis, that reserve in neighboring regions (even when separated by a distance of several tissue samples) was significantly correlated. This also applied to patterns of resting myocardial flow. Thus, both resting coronary blood flow and reserve appear to be locally continuous and may define functional

  5. Heat Flow Pattern in the Mainland of China and Its Geodynamic Significance

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    On the basis of 723 heat flow measurements in the mainland of China and over 2000 data from the global heat flow data set, the authors compiled the heat flow map of the mainland of China and its adjacent areas to exhibit the overall variation of the heat flow pattern in the mainland. The heat flow pattern of the mainland is complex, and can not be simply summarized as "low in the north and west and high in the south and east". Significant difference exists between eastern and western China in the spatial pattern of heat flow. Divided by the 105° E meridian, heat flow values in eastern China show a westward-decreasing trend; and a northward variation is observed in western China. The high-heat flow regions correspond to tectonically active belts such as Cenozoic orogens and extensional basins, where mantle heat flow is high; and the low-heat flow regions correspond to stable units such as the Tarim and Yangtze platforms. This heat flow pattern is controlled by India-Asia collision in the west and Pacific plate subduction in the east. The lateral variation in lithospheric strength corresponds to the heat flow variation, and there is a generally reversely proportional relation between heat flow and lithospheric strength in the mainland of China. The mosaic pattern of present deformation in the mainland results from lateral rheological heterogeneity. The good coincidence between weak strength domains and seismic zones demonstrates the intrinsic relation between the strength heterogeneity and regional seismicity pattern in the mainland of China.

  6. Parametric Study of Flow Patterns behind the Standing Accretion Shock Wave for Core-Collapse Supernovae

    CERN Document Server

    Iwakami, Wakana; Yamada, Shoichi

    2013-01-01

    The systematic research of flow patterns behind the accretion shock wave is conducted using three-dimensional hydrodynamics simulations for core-collapse supernovae in this study. Changing the accretion rate and neutrino luminosity, the steady solutions of the one-dimensional irrotational accretion flow passing through the spherical shock wave are evolved by imposing a random perturbation with 1% amplitude at the onset of the simulations. Depending on the accretion rate and neutrino luminosity, various flow patterns appear behind the shock wave. We classified them into the three fundamental flow patterns: (1) sloshing motion, (2) spiral motion, (3) multiple high-entropy bubbles, and the two anomalous flow patterns: (4) spiral motion with buoyant bubbles, and (5) spiral motion with pulsating rotational velocity. The sloshing and spiral motions tend to be dominant in the higher accretion rate and lower neutrino luminosity, and the generations of multiple buoyant bubbles tend to prevail in the lower accretion ra...

  7. A Comparative Study on Temperature Control of CSTR using PI Controller, PID Controller and PID (Two Degree of Freedom Controller

    Directory of Open Access Journals (Sweden)

    Bikash Dey

    2014-01-01

    Full Text Available This paper present three different control strategies based on PI Control, PID control and Two degree of freedom PID control for Continuous Stirred Tank Reactor (CSTR.CSTR which offers a diverse range of application in the field of chemical engineering as well as in the control engineering and is an attractive research area for process control researchers. Our objective is to control the temperature of CSTR in presence of the set point. MATLAB SIMULINK software is used for model design and simulation

  8. Debris flows in the Eastern Italian Alps: seasonality and atmospheric circulation patterns

    Directory of Open Access Journals (Sweden)

    E. I. Nikolopoulos

    2014-12-01

    Full Text Available The work examines the seasonality and large-scale atmospheric circulation patterns of debris flows in the Trentino-Alto Adige region (Eastern Italian Alps. Analysis is based on classification algorithms applied on a uniquely dense archive of debris flows and hourly rain gauge precipitation series covering the period 2000–2009. Results highlight the seasonal and synoptic forcing patterns linked to debris flows in the study area. Summer and fall season account for 92% of the debris flows in the record, while atmospheric circulation characterized by Zonal West, Mixed and Meridional South, Southeast patterns account for 80%. Both seasonal and circulation patterns exhibit geographical preference. In the case of seasonality, there is a strong north–south separation of summer–fall dominance while spatial distribution of dominant circulation patterns exhibits clustering, with both Zonal West and Mixed prevailing in the northwest and central east part of the region, while the southern part relates to Meridional South, Southeast pattern. Seasonal and synoptic pattern dependence is pronounced also on the debris flow triggering rainfall properties. Examination of rainfall intensity–duration thresholds derived for different data classes (according to season and synoptic pattern revealed a distinct variability in estimated thresholds. These findings imply a certain control on debris-flow events and can therefore be used to improve existing alert systems.

  9. Two-phase flow patterns characteristics analysis based on image and conductance sensors

    Science.gov (United States)

    Wang, Zhenya; Jin, Ningde; Wang, Chun; Wang, Jinxiang

    2008-10-01

    In order to study the temporal and spatial evolution characteristics of gas-liquid two-phase flow pattern, the two-phase flow monitoring system composed of high-speed dynamic camera and Vertical Multi-Electrode Array conductance sensor (VMEA) was utilized to shoot dynamic images and acquire the conductance fluctuating signals of 5 typical vertical gas-liquid two-phase flow patterns in a 125mm i.d. upward pipe. Gray level co-occurrence matrix (GLCM) was used to extract four time-varying characteristic parameter indices which represented different flow image texture structures and also Lempel-Ziv complexity of them were calculated. Then the transition of flow structure and flow property were comprehensively analyzed, combining the result derived from image information with recurrence plots (RPs) and Lempel-Ziv complexity of conductance fluctuating signals. The study showed that the line texture structure of RPs enabled to indicate flow pattern characteristics; the flow image texture structure characteristic parameters sequence described the variance of flow structure and dynamical complexity of different flow patterns.

  10. Robust PCA-Based Abnormal Traffic Flow Pattern Isolation and Loop Detector Fault Detection

    Institute of Scientific and Technical Information of China (English)

    JIN Xuexiang; ZHANG Yi; LI Li; HU Jianming

    2008-01-01

    One key function of intelligent transportation systems is to automatically detect abnormal traffic phenomena and to help further investigations of the cause of the abnormality. This paper describes a robust principal components analysis (RPCA)-based abnormal traffic flow pattern isolation and loop detector fault detection method. The results show that RPCA is a useful tool to distinguish regular traffic flow from abnor-mal traffic flow patterns caused by accidents and loop detector faults. This approach gives an effective traffic flow data pre-processing method to reduce the human effort in finding potential loop detector faults. The method can also be used to further investigate the causes of the abnormality.

  11. The physics of stripe patterns in turbulent channel flow determined by DNS results

    CERN Document Server

    Kiš, P; Herwig, H

    2015-01-01

    The turbulent flow in an infinitely extended plane channel is analysed by solving the Navier-Stokes equations with a DNS approach. Solutions are obtained in a numerical solution domain of finite size in the streamwise as well as in the lateral direction setting periodic boundary conditions in both directions. Their impact on large scale structures in the turbulent flow field is analysed carefully in order to avoid their suppression. When this is done appropriately well known stripe patterns in these flows can be observed and analysed especially with respect to their relative motion compared to the mean flow velocity. Various details of this stripe pattern dominated velocity field are shown. Also global parameters like the friction factor in the flow field and the Nusselt number in the temperature field are determined based on the statistics of the flow and temperature data in a very large time period that guarantees fully developed turbulent flow and heat transfer.

  12. Children's Brain Responses to Optic Flow Vary by Pattern Type and Motion Speed.

    Directory of Open Access Journals (Sweden)

    Rick O Gilmore

    Full Text Available Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction at three different speeds (2, 4, and 8 deg/s. Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood.

  13. Use of laminar flow patterning for miniaturised biochemical assays

    DEFF Research Database (Denmark)

    Regenberg, Birgitte; Krühne, Ulrich; Beyer, M.

    2004-01-01

    Laminar flow in microfluidic chambers was used to construct low (one dimensional) density arrays suitable for miniaturized biochemical assays. By varying the ratio of flows of two guiding streams flanking a sample stream, precise focusing and positioning of the latter was achieved, and reactive...... species carried in the sample stream were deposited on functionalized chip surfaces as discrete 50 mm wide lanes. Using different model systems we have confirmed the method's suitability for qualitative screening and quantification tasks in receptor-ligand assays, recording biotin......-streptavidin interactions, DNA-hybridization and DNA-triplex formation. The system is simple, fast, reproducible, flexible, and has small sample requirements....

  14. Echocardiographic and hemodynamic determinants of right coronary artery flow reserve and phasic flow pattern in advanced non-ischemic cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Mady Charles

    2007-09-01

    Full Text Available Abstract Background In patients with advanced non-ischemic cardiomyopathy (NIC, right-sided cardiac disturbances has prognostic implications. Right coronary artery (RCA flow pattern and flow reserve (CFR are not well known in this setting. The purpose of this study was to assess, in human advanced NIC, the RCA phasic flow pattern and CFR, also under right-sided cardiac disturbances, and compare with left coronary circulation. As well as to investigate any correlation between the cardiac structural, mechanical and hemodynamic parameters with RCA phasic flow pattern or CFR. Methods Twenty four patients with dilated severe NIC were evaluated non-invasively, even by echocardiography, and also by cardiac catheterization, inclusive with Swan-Ganz catheter. Intracoronary Doppler (Flowire data was obtained in RCA and left anterior descendent coronary artery (LAD before and after adenosine. Resting RCA phasic pattern (diastolic/systolic was compared between subgroups with and without pulmonary hypertension, and with and without right ventricular (RV dysfunction; and also with LAD. RCA-CFR was compared with LAD, as well as in those subgroups. Pearson's correlation analysis was accomplished among echocardiographic (including LV fractional shortening, mass index, end systolic wall stress more hemodynamic parameters with RCA phasic flow pattern or RCA-CFR. Results LV fractional shortening and end diastolic diameter were 15.3 ± 3.5 % and 69.4 ± 12.2 mm. Resting RCA phasic pattern had no difference comparing subgroups with vs. without pulmonary hypertension (1.45 vs. 1.29, p = NS either with vs. without RV dysfunction (1.47 vs. 1.23, p = NS; RCA vs. LAD was 1.35 vs. 2.85 (p Conclusion In patients with chronic advanced NIC, RCA phasic flow pattern has a mild diastolic predominance, less marked than in LAD, with no effects from pulmonary artery hypertension or RV dysfunction. There is no significant correlation between any cardiac mechanical-structural or

  15. Extended continuous-flow stirred-tank reactor (ECSTR) as a simple model of life under thermodynamically open conditions

    Science.gov (United States)

    Takinoue, Masahiro; Ma, Yue; Mori, Yoshihito; Yoshikawa, Kenichi

    2009-07-01

    A continuous-flow stirred-tank reactor (CSTR) is a vital tool for investigating the nonlinear dynamics of chemical systems. This report proposes an extended CSTR (ECSTR) inspired by active and passive transports through a closed membrane in living systems. In addition to the externally-controlled flow in a conventional CSTR, we introduce passive diffusion through a membrane into the ECSTR. This extension allows us to control the chemical dynamics with a larger parameter-dimension. Numerical analyses show that the ECSTR can expand an oscillatory region in the parameter space and can convert a non-oscillatory chemical system to an oscillatory system.

  16. Wave-induced nearshore flow patterns in the vicinity of Cochin harbour, India

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Vethamony, P.; Murty, C.S.

    of a sheared cellular flow pattern with clockwise and anti-clockwise rotations exhibiting noticeable spatial variation. Field studies reveal a southerly littoral current during most of the year. A conceptual model is presented to explain the sediment...

  17. Thermal structure and flow patterns around Seychelles group of Islands (Indian Ocean) during austral autumn

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; RameshBabu, V.; RameshKumar, M.R.

    Properties of thermal structure in the upper 750 m around the Seychelles group of islands in the Indian Ocean, based on Expendable Bathythermograph (XBT) data collected in March 1984, are presented along with the inferred flow patterns...

  18. Cantorian Fractal Patterns, Quantum-Like Chaos and Prime Numbers in Atmospheric Flows

    CERN Document Server

    Selvam, A M; Fadnavis, Suvarna

    1998-01-01

    Atmospheric flows exhibit cantorian fractal space-time fluctuations signifying long-range spatiotemporal correlations. A recently developed cell dynamical system model shows that such non-local connections are intrinsic to quantum-like chaos governing flow dynamics. The dynamical evolution of fractal structures can be quantified in terms of ordered energy flow described by mathematical functions which occur in the field of number theory. The quantum-like chaos in atmospheric flows can be quantified in terms of the following mathematical functions / concepts: (1) The fractal structure of the flow pattern is resolved into an overall logarithmic spiral trajectory with the quasiperiodic Penrose tiling pattern for the internal structure and is equivalent to a hierarchy of vortices. The incorporation of Fibonacci mathematical series, representative of ramified bifurcations, indicates ordered growth of fractal patterns. (2) The steady state emergence of progressively larger fractal structures incorporates unique pri...

  19. 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.

  20. Topological analysis of the formation of Jet-Wake flow pattern in centrifugal impeller channel

    Institute of Scientific and Technical Information of China (English)

    ZHENG Qun; LIU Shun-long

    2004-01-01

    Topological analyses are carried out for the numerical results of internal flow field in centrifugal impeller. Topological rules of the singular point characteristics of the limiting streamline are derived and used to determine three dimensional separation patterns in centrifugal impeller and to verify the numerical results. The results reveal that the wake is saddle to nodal closed separation and the formation, its onset point and its developing process of Jet-Wake Flow pattern in centrifugal impeller are presented in this paper.

  1. Flow-Induced Control of Pattern Formation in Chemical Systems

    Science.gov (United States)

    Berenstein, Igal; Beta, Carsten

    Since Alan Turing's seminal paper in 1952, the study of spatio-temporal patterns that arise in systems of reacting and diffusing components has grown into an immense and vibrant realm of scientific research. This field includes not only chemical systems but spans many areas of science as diverse as cell and developmental biology, ecology, geosciences, or semiconductor physics. For several decades research in this field has concentrated on the vast variety of patterns that can emerge in reaction-diffusion systems and on the underlying instabilities. In the 1990s, stimulated by the pioneering work of Ott, Grebogi and Yorke, control of pattern formation arose as a new topical focus and gradually developed into an entire new field of research. On the one hand, research interests concentrated on control and suppression of undesired dynamical states, in particular on control of chaos. On the other hand, the design and engineering of particular space-time patterns became a major focus in this field that motivates ongoing scientific effort until today...

  2. Umbilical blood flow patterns directly after birth before delayed cord clamping.

    Science.gov (United States)

    Boere, I; Roest, A A W; Wallace, E; Ten Harkel, A D J; Haak, M C; Morley, C J; Hooper, S B; te Pas, A B

    2015-03-01

    Delayed umbilical cord clamping (DCC) affects the cardiopulmonary transition and blood volume in neonates immediately after birth. However, little is known of blood flow in the umbilical vessels immediately after birth during DCC. The objective is to describe the duration and patterns of blood flow through the umbilical vessels during DCC. Arterial and venous umbilical blood flow was measured during DCC using Doppler ultrasound in uncomplicated term vaginal deliveries. Immediately after birth, the probe was placed in the middle of the umbilical cord, pattern and duration of flow in vein and arteries were evaluated until cord clamping. Thirty infants were studied. Venous flow: In 10% no flow was present, in 57% flow stopped at 4:34 (3:03-7:31) (median (IQR) min:sec) after birth, before the cord was clamped. In 33%, flow continued until cord clamping at 5:13 (2:56-9:15) min:sec. Initially, venous flow was intermittent, increasing markedly during large breaths or stopping and reversing during crying, but then became continuous. Arterial flow: In 17% no flow was present, in 40% flow stopped at 4:22 (2:29-7:17) min:sec, while cord pulsations were still palpable. In 43% flow continued until the cord was clamped at 5:16 (3:32-10:10) min:sec. Arterial flow was pulsatile, unidirectional towards placenta or bidirectional to/from placenta. In 40% flow became continuous towards placenta later on. During delayed umbilical cord clamping, venous and arterial umbilical flow occurs for longer than previously described. Net placental transfusion is probably the result of several factors of which breathing could play a major role. Umbilical flow is unrelated to cessation of pulsations. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  3. Vapor Flow Patterns During a Start-Up Transient in Heat Pipes

    Science.gov (United States)

    Issacci, F.; Ghoniem, N, M.; Catton, I.

    1996-01-01

    The vapor flow patterns in heat pipes are examined during the start-up transient phase. The vapor core is modelled as a channel flow using a two dimensional compressible flow model. A nonlinear filtering technique is used as a post process to eliminate the non-physical oscillations of the flow variables. For high-input heat flux, multiple shock reflections are observed in the evaporation region. The reflections cause a reverse flow in the evaporation and circulations in the adiabatic region. Furthermore, each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heat pipe.

  4. Surface Patterning: Controlling Fluid Flow Through Dolphin and Shark Skin Biomimicry

    Science.gov (United States)

    Gamble, Lawren; Lang, Amy; Bradshaw, Michael; McVay, Eric

    2013-11-01

    Dolphin skin is characterized by circumferential ridges, perpendicular to fluid flow, present from the crest of the head until the tail fluke. When observing a cross section of skin, the ridges have a sinusoidal pattern. Sinusoidal grooves have been proven to induce vortices in the cavities that can help control flow separation which can reduce pressure drag. Shark skin, however, is patterned with flexible scales that bristle up to 50 degrees with reversed flow. Both dolphin ridges and shark scales are thought to help control fluid flow and increase swimming efficiency by delaying the separation of the boundary layer. This study investigates how flow characteristics can be altered with bio-inspired surface patterning. A NACA 4412 hydrofoil was entirely patterned with transverse sinusoidal grooves, inspired by dolphin skin but scaled so the cavities on the model have the same Reynolds number as the cavities on a swimming shark. Static tests were conducted at a Reynolds number of approximately 100,000 and at varying angles of attack. The results were compared to the smooth hydrofoil case. The flow data was quantified using Digital Particle Image Velocimetry (DPIV). The results of this study demonstrated that the patterned hydrofoil experienced greater separation than the smooth hydrofoil. It is hypothesize that this could be remediated if the pattern was placed only after the maximum thickness of the hydrofoil. Funding through NSF REU grant 1062611 is gratefully acknowledged.

  5. APPLICATION OF CSTR-SBR PROCESS IN TREATMENT OF ANIMAL WASTEWATER%CSTR-SBR工艺在畜禽废水处理中的应用

    Institute of Scientific and Technical Information of China (English)

    林伟华; 蔡昌达

    2003-01-01

    针对当前我国规模化养殖场排放污染物的特点,以实际工程为例,介绍了"CSTR+SBR"工艺在畜禽废水处理中的设计及其运行情况.其中好氧反应池的脱氮效果特别理想,达99%以上,而且合理的池型结构确保了良好的出水效果,供同类工程参考.

  6. Nitrogen transformations in wetlands: Effects of water flow patterns

    Energy Technology Data Exchange (ETDEWEB)

    Davidsson, T.

    1997-11-01

    In this thesis, I have studied nitrogen turnover processes in water meadows. A water meadow is a wetland where water infiltrates through the soil of a grassland field. It is hypothesized that infiltration of water through the soil matrix promotes nutrient transformations compared to surface flow of water, by increasing the contact between water, nutrients, soil organic matter and bacteria. I have studied how the balance between nitrogen removal (denitrification, assimilative uptake, adsorption) and release (mineralization, desorption) processes are affected by water flow characteristics. Mass balance studies and direct denitrification measurements at two field sites showed that, although denitrification was high, net nitrogen removal in the water meadows was poor. This was due to release of ammonium and dissolved organic nitrogen (DON) from the soils. In laboratory studies, using {sup 15}N isotope techniques, I have shown that nitrogen turnover is considerably affected by hydrological conditions and by soil type. Infiltration increased virtually all the nitrogen processes, due to deeper penetration of nitrate and oxygen, and extended zones of turnover processes. On the contrary, soils and sediments with surface water flow, diffusion is the main transfer mechanism. The relation between release and removal processes sometimes resulted in shifts towards net nitrogen production. This occurred in infiltration treatments when ammonium efflux was high in relation to denitrification. It was concluded that ammonium and DON was of soil origin and hence not a product of dissimilatory nitrate reduction to ammonium. Both denitrification potential and mineralization rates were higher in peaty than in sandy soil. Vertical or horizontal subsurface flow is substantial in many wetland types, such as riparian zones, tidal salt marshes, fens, root-zone systems and water meadows. Moreover, any environment where aquatic and terrestrial ecosystems meet, and where water level fluctuates

  7. OPTIMIZATION OF COAL PARTICLE FLOW PATTERNS IN LOW NOX BURNERS

    Energy Technology Data Exchange (ETDEWEB)

    Jost O.L. Wendt; Gregory E. Ogden; Jennifer Sinclair; Stephanus Budilarto

    2001-09-04

    It is well understood that the stability of axial diffusion flames is dependent on the mixing behavior of the fuel and combustion air streams. Combustion aerodynamic texts typically describe flame stability and transitions from laminar diffusion flames to fully developed turbulent flames as a function of increasing jet velocity. Turbulent diffusion flame stability is greatly influenced by recirculation eddies that transport hot combustion gases back to the burner nozzle. This recirculation enhances mixing and heats the incoming gas streams. Models describing these recirculation eddies utilize conservation of momentum and mass assumptions. Increasing the mass flow rate of either fuel or combustion air increases both the jet velocity and momentum for a fixed burner configuration. Thus, differentiating between gas velocity and momentum is important when evaluating flame stability under various operating conditions. The research efforts described herein are part of an ongoing project directed at evaluating the effect of flame aerodynamics on NO{sub x} emissions from coal fired burners in a systematic manner. This research includes both experimental and modeling efforts being performed at the University of Arizona in collaboration with Purdue University. The objective of this effort is to develop rational design tools for optimizing low NO{sub x} burners. Experimental studies include both cold-and hot-flow evaluations of the following parameters: primary and secondary inlet air velocity, coal concentration in the primary air, coal particle size distribution and flame holder geometry. Hot-flow experiments will also evaluate the effect of wall temperature on burner performance.

  8. Numerical analysis of respiratory flow patterns within human upper airway

    Science.gov (United States)

    Wang, Ying; Liu, Yingxi; Sun, Xiuzhen; Yu, Shen; Gao, Fei

    2009-12-01

    A computational fluid dynamics (CFD) approach is used to study the respiratory airflow dynamics within a human upper airway. The airway model which consists of the airway from nasal cavity, pharynx, larynx and trachea to triple bifurcation is built based on the CT images of a healthy volunteer and the Weibel model. The flow characteristics of the whole upper airway are quantitatively described at any time level of respiratory cycle. Simulation results of respiratory flow show good agreement with the clinical measures, experimental and computational results in the literature. The air mainly passes through the floor of the nasal cavity in the common, middle and inferior nasal meatus. The higher airway resistance and wall shear stresses are distributed on the posterior nasal valve. Although the airways of pharynx, larynx and bronchi experience low shear stresses, it is notable that relatively high shear stresses are distributed on the wall of epiglottis and bronchial bifurcations. Besides, two-dimensional fluid-structure interaction models of normal and abnormal airways are built to discuss the flow-induced deformation in various anatomy models. The result shows that the wall deformation in normal airway is relatively small.

  9. Secondary Flow Patterns of Liquid Ejector with Computational Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kwisung; Yun, Jinwon; Yu, Sangseok [Chungnam National University, Daejeon (Korea, Republic of); Sohn, Inseok [COAVIS, Sejong (Korea, Republic of); Seo, Yongkyo [Korea Automotive Technology Institute, Cheonan (Korea, Republic of)

    2015-02-15

    An ejector is a type of non-powered pump that is used to supply a secondary flow via the ejection of a primary flow. It is utilized in many industrial fields, and is used for fueling the vehicle because of less failures and simple structure. Since most of ejectors in industry are gas-to-gas and liquid to gas ejector, many research activities have been reported in optimization of gas ejector. On the other hand, the liquid ejector is also applied in many industry but few research has been reported. The liquid ejector occurs cavitation, and it causes damage of parts. Cavitation has bees observed at the nozzle throat at the specified pressure. In this study, a two-dimensional axisymmetric simulation of a liquid-liquid ejector was carried out using five different parameters. The angle of the nozzle plays an important role in the cavitation of a liquid ejector, and the performance characteristics of the flow ratio showed that an angle of 35° was the most advantageous. The simulation results showed that the performance of the liquid ejector and the cavitation effect have to be considered simultaneously.

  10. Effects of Orifice Orientation and Gas-Liquid Flow Pattern on Initial Bubble Size

    Institute of Scientific and Technical Information of China (English)

    刘长军; 梁斌; 唐盛伟; 闵恩泽

    2013-01-01

    In many gas-liquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gas-liquid flow pattern. Bubble formation models for variant gas-liquid flow pat-terns have been developed based on force balance. The effects of the orientation of gas-liquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient air-water system, the suitable gas-liquid flow pattern is important to obtain smaller bubbles under the low velocity liquid cross-flow con-ditions with stainless steel spargers. Among the four types of gas-liquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found to be insignificant when liquid velocity is higher than 3.2 m·s-1 or the orifice diameter is small enough.

  11. Scaling analysis of gas-liquid two-phase flow pattern in microgravity

    Science.gov (United States)

    Lee, Jinho

    1993-01-01

    A scaling analysis of gas-liquid two-phase flow pattern in microgravity, based on the dominant physical mechanism, was carried out with the goal of predicting the gas-liquid two-phase flow regime in a pipe under conditions of microgravity. The results demonstrated the effect of inlet geometry on the flow regime transition. A comparison of the predictions with existing experimental data showed good agreement.

  12. The Effect of Confluence Angle on the Flow Pattern at a Rectangular Open-Channel

    Directory of Open Access Journals (Sweden)

    F. Rooniyan

    2014-02-01

    Full Text Available Flow connection in channels is a phenomenon which frequently happens in rivers, water and drainage channels and urban sewage systems. The phenomenon appears to be more complex in rivers than in channels, especially at the y-junction bed joint that causes erosion and sedimentation at some areas resulting to morphological changes. Flow behavior at the channel junction area depends on variables such as channel geometry, discharge ratio, tributary width and y-junction connection angle of the channel, bed level changes at the bed joint, flow characteristic at the bed joint upstream and flow Froude number in different sections. In this research, fluent numerical model and junction angles of 30o, 45o & 60o are used to analyze and evaluate the effect of channel junction geometry on the flow pattern and the flow separation zone dimensions in different ratios of flow discharge (upstream channel discharge to total discharge of the flow. Results for two ratios of flow discharge are represented. Results are in agreement with earlier studies and it is shown that the change of the channel crossing angle affects the flow pattern in the main channel and also that the dimensions of the created separation zone in the main channel become larger when the crossing angle increases. This phenomenon can also be observed when the flow discharge ratio is lower. Analysis showed that the least dimension of the separation zone will be at the crossing angle of 45o .

  13. Flow patterns and their transition characteristicsof the air-water two-phase flow in a horizontal pipe with asudden-changed cross-section area

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Flow patterns in upstream and downstream straight tubes of sudden-changedareas in ahorizontal straight pipe were experimentally examined. Both sudden-expansioncross-section (SECS)and sudden-contraction cross-section (SCCS) were investigated. The flow pattern mapsupstream anddownstream were delineated and compared with those in straight tubes with uniformcross-sections.The effects of the SECS and SCCS on flow patterns were discussed and analyzed.Furthermore, flowpattern transition mechanisms resulting in occurrences of different flow patternswere simplydiscussed and some transition criteria for the flow pattern transitions were deduced byusing the non-dimensionlized analysis method.

  14. Assessment of spatial flow patterns in unsaturated sandy alluvial sediments using high- resolution GPR.

    Science.gov (United States)

    Haarder, E. B.; Looms, M. C.; Nielsen, L.; Jensen, K. H.

    2008-12-01

    Traditional sampling and monitoring techniques have inherent limitations in capturing the detailed spatial patterns of water flow in the unsaturated zone particularly for complex flow conditions such as unstable wetting fronts or preferential flow. Dye tracer experiments can help visualise the dynamics of water flow but they are highly destructive as well. High-resolution Ground Penetrating Radar (GPR) is an attractive technique for non-destructive mapping of soil moisture changes and thus flow patterns in the shallow subsurface. In this study we test the method at a field site in western Denmark developed on a sandy alluvial outwash plane. We compare high-resolution reflection GPR data with visual observations from a dye tracer experiment using Brilliant Blue (BB). 100 mm of BB-stained water was infiltrated over a 5x5 m area and 3D reflection GPR data sets using high-frequency antennae were collected before and after infiltration. Subsequently a 2 m deep trench was excavated for visual observations of the flow patterns in a cross-section as evidenced by the dye staining patterns. The dye infiltration experiment had an overall attenuating effect on the GPR signal, and reflections were delayed significantly because of the increase in soil moisture. In the excavated cross-section we found a reasonable agreement between the areas subject to attenuation of the GPR signal and the areas affected by dye. Also, we found that displacement flow was responsible for a delay of deeper reflections below the extend of the dye staining. An amplitude analysis performed for a shallow 1.3 m thick section shows a general decrease in electromagnetic wave amplitude within the region bounded by the area exposed to infiltration, but also suggests that lateral flow along sedimentary boundaries occurs. The results suggest that high-resolution GPR provides important insight into the spatial patterns of unsaturated flow and highlight the applicability of this method as a non-destructive means

  15. Performance of continuous stirred tank reactor (CSTR) on fermentative biohydrogen production from melon waste

    Science.gov (United States)

    Cahyari, K.; Sarto; Syamsiah, S.; Prasetya, A.

    2016-11-01

    This research was meant to investigate performance of continuous stirred tank reactor (CSTR) as bioreactor for producing biohydrogen from melon waste through dark fermentation method. Melon waste are commonly generated from agricultural processing stages i.e. cultivation, post-harvesting, industrial processing, and transportation. It accounted for more than 50% of total harvested fruit. Feedstock of melon waste was fed regularly to CSTR according to organic loading rate at value 1.2 - 3.6 g VS/ (l.d). Optimum condition was achieved at OLR 2.4 g VS/ (l.d) with the highest total gas volume 196 ml STP. Implication of higher OLR value is reduction of total gas volume due to accumulation of acids (pH 4.0), and lower substrate volatile solid removal. In summary, application of this method might valorize melon waste and generates renewable energy sources.

  16. Perancangan dan Simulasi MRAC untui Proses Pengendalian Temperatur pada Continuous Stirred Tank Reactor (CSTR

    Directory of Open Access Journals (Sweden)

    Amelia Sylvia

    2014-03-01

    Full Text Available Temperatur merupakan salah satu variabel proses dasar yang dikendalikan untuk menjaga suhu cairan di dalam reaktor. Model Reference Adaptive Controller (MRAC dengan MIT rule dipilih untuk mencapai spesifikasi respon yang diinginkan pada CSTR. Beban yang bervariasi berupa debit aliran likuid yang masuk ke dalam reaktor dapat menyebabkan perubahan parameter yang mempengaruhi perubahan temperatur output produk pada CSTR. Sebuah simulasi dilakukan dengan menggunakan MATLAB dan hasilnya dianalisa. Respon plant dapat melakukan adaptasi parameter – parameter kontrolernya cukup baik pada nilai gain adaptasi dengan rentang 0.00000010000 sampai 0.00000000001. Waktu yang dibutuhkan untuk mengatasi beban yang bervariasi berupa debit aliran yang masuk ke dalam reaktor dengan nilai yang maksimal (1.5 m^3/min menghasilkan respon plant lebih cepat 42 detik dari pada debit aliran masuk dengan nilai yang nominal (1 m^3/min 63 detik dan minimal (0.5 m^3/min 75 detik.

  17. Flow patterns on spectral-domain optical coherence tomography reveal flow directions at retinal vessel bifurcations

    DEFF Research Database (Denmark)

    Willerslev, Anne; Li, Xiao Q; Munch, Inger C

    2014-01-01

    PURPOSE: To study intravascular characteristics of flowing blood in retinal vessels using spectral-domain optical coherence tomography (SD-OCT). METHODS: Examination of selected arterial bifurcations and venous sites of confluence in 25 healthy 11-year-old children recruited as an ad hoc subsample...... be determined using SD-OCT. This feature may assist the identification of flow reversal near sites of vascular occlusion, the analysis of blood flow near vascular malformations and the segmentation of retinal SD-OCT images....

  18. Use of the Riccatti Equation On-Line for Adaptively Controlling a CSTR Chemical Reactor.

    OpenAIRE

    Edwards, J B; Mohd Noor, S.B.

    1995-01-01

    An idealised nonlinear model of an isothermal continuous stirred-tank reactor (CSTR) is analysed and simulated for optimal control based on the continuous on-line recomputation of a Riccati Controller as proposed by Banks (1). The controller and resulting behaviour are derived analytically and confirmed to be optimal by derivation also via Dynamic Programming. For comparison purposes, the behaviour of the same model under linear proportional control (with feedforward compensation)is derived a...

  19. Pattern formation in directional solidification under shear flow. II. Morphologies and their characterization.

    Science.gov (United States)

    Marietti, Y; Debierre, J M; Bock, T M; Kassner, K

    2001-06-01

    In the preceding paper, we have established an interface equation for directional solidification under the influence of a shear flow parallel to the interface. This equation is asymptotically valid near the absolute stability limit. The flow, described by a nonlocal term, induces a lateral drift of the whole pattern due to its symmetry-breaking properties. We find that at not-too-large flow strengths, the transcritical nature of the transition to hexagonal patterns shows up via a hexagonal modulation of the stripe pattern even when the linear instability threshold of the flowless case has not yet been attained. When the flow term is large, the linear description of the drift velocity breaks down and transitions to flow-dominated morphologies take place. The competition between flow-induced and diffusion-induced patterns (controlled by the temperature gradient) leads to new phenomena such as the transition to a different lattice structure in an array of hexagonal cells. Several methods to characterize the morphologies and their transitions are investigated and compared. In particular, we consider two different ways of defining topological defects useful in the description of patterns and we discuss how they are related to each other.

  20. Mapping Reactive Flow Patterns in Monolithic Nanoporous Catalysts

    CERN Document Server

    Falcucci, Giacomo; Montessori, Andrea; Melchionna, Simone; Prestininzi, Pietro; Barroo, Cedric; Bell, David C; Biener, Monika M; Biener, Juergen; Zugic, Branko; Kaxiras, Efthimios

    2016-01-01

    The development of high-efficiency porous catalyst membranes critically depends on our understanding of where the majority of the chemical conversions occur within the porous structure. This requires mapping of chemical reactions and mass transport inside the complex nano-scale architecture of porous catalyst membranes which is a multiscale problem in both the temporal and spatial domain. To address this problem, we developed a multi-scale mass transport computational framework based on the Lattice Boltzmann Method (LBM) that allows us to account for catalytic reactions at the gas-solid interface by introducing a new boundary condition. In good agreement with experiments, the simulations reveal that most catalytic reactions occur near the gas-flow facing side of the catalyst membrane if chemical reactions are fast compared to mass transport within the porous catalyst membrane.

  1. Electrical Capacitance Tomography Measurement of Flow Patterns and Film Thickness in a Thermosyphon

    Institute of Scientific and Technical Information of China (English)

    Jingtao LI; Qi CHEN; Xiangyuan DONG; Shi LIU

    2005-01-01

    An experimental study was performed to evaluate the suitability of using an electrical capacitance tomography (ECT) system to visualize the flow patterns, and to measure the film thickness of the annular flow in a two-phase closed thermosyphon (TPCT). The performance of the ECT system was examined over a range of flow conditions.The experimental data were compared with the visual observations and existing correlations. Results indicated that the ECT system, with the linear back projection (LBP) algorithm, could be used to give an on-line qualitative image of the flow patterns. The Landweber iteration algorithm with optimal step length was implemented off-line to reconstruct high-resolution images. Then, the images were analyzed to obtain the film thickness of the annular flow. The experimental data compared well with the Nusselt's equation in low vapor velocity range, but showed an increasing deficiency with the increase of vapor velocity.

  2. Mode pattern of internal flow in a water droplet on a vibrating hydrophobic surface.

    Science.gov (United States)

    Kim, Hun; Lim, Hee-Chang

    2015-06-01

    The objective of this study is to understand the mode pattern of the internal flow in a water droplet placed on a hydrophobic surface that periodically and vertically vibrates. As a result, a water droplet on a vibrating hydrophobic surface has a typical shape that depends on each resonance mode, and, additionally, we observed a diversified lobe size and internal flows in the water droplet. The size of each lobe at the resonance frequency was relatively greater than that at the neighboring frequencies, and the internal flow of the nth order mode was also observed in the flow visualization. In general, large symmetrical flow streams were generated along the vertical axis in each mode, with a large circulating movement from the bottom to the top, and then to the triple contact line along the droplet surface. In contrast, modes 2 and 4 generated a Y-shaped flow pattern, in which the flow moved to the node point in the lower part of the droplet, but modes 6 and 8 had similar patterns, with only a little difference. In addition, as a result of the PIV measurement, while the flow velocity of mode 4 was faster than that of model 2, those of modes 6 and 8 were almost similar.

  3. H(2) production through anaerobic mixed culture: effect of batch S(0)/X(0) and shock loading in CSTR.

    Science.gov (United States)

    Fan, Kuo-Shuh; Chen, Ya-Yun

    2004-12-01

    Biological production of H(2) has received considerable attention lately. The present study was undertaken to observe the effects of substrate/seeding ratios (S(0)/X(0)) on batch H(2) generation. The H(2)-producing seeding spores were obtained from the heat treatment (88 degrees C for 12h) of the compost from a grass composting facility. A dehydrated brewery mixture was used as feed substrate. The results indicate that the pattern of the cumulative H(2) production with time is similar to the growth curve with a typical lag, exponential and stationary phase; the results were successfully modeled with a modified Gompertz equation. It appears that maximum H(2) yield potential (27ml g(-1)COD(added)) occurs at an S(0)/X(0) ratio of about 4, whereas the maximum specific H(2) yield (205ml g(-1) VSSd(-1)) occurs at approximately S(0)/X(0)=3. The S(0)/X(0) ratios higher than 4 would inhibit H(2) production. An attempt was made to waste a certain amount of reactor content and replaced it with fresh substrate in order to enhance H(2) production. After this medium replacement, the H(2) production was initially inhibited and the system then exhibited a long lag before it reached an active H(2) production stage. For a continuous-stirred tank-reactor (CSTR) system, the results of replacing 25% of the reactor content indicate that there is still a lag time before a sudden increase in H(2) production after the addition of the new substrate feed. The major low molecular weight acids identified are HAc and HBu with total volatile acids of about 6000-8000mg l(-1). The ratio of HAc/HBu in the present study is relatively constant (about 5) and appears not significantly affected by the medium replacement. The concentration of total alcohols is about 2000mg l(-1). All in all, the CSTR system is able to recover to its previous performance after such a dramatic 25% medium replacement.

  4. Influence of flow patterns on chromatographic efficiency in centrifugal partition chromatography.

    Science.gov (United States)

    Marchal, L; Foucaul, A; Patissier, G; Rosant, J M; Legrand, J

    2000-02-11

    Visualization of flow patterns in centrifugal partition chromatography (CPC) was performed with an asynchronous camera and a stroboscope triggered by the CPC rotor, allowing a channel to be selected and observed regardless of rotational speed. Three main types of flow states were noted as a function of rotational speed and flow-rate: jets stuck along channel walls, broken jets and atomization. Our observations emphasize the importance of Coriolis force on flow shape. Chromatographic efficiency was related to the dispersion of the mobile phase in the stationary phase.

  5. Unsteady Tip Clearance Flow Pattern in an Isolated Axial Compressor Rotor with Micro Tip Injection

    Institute of Scientific and Technical Information of China (English)

    Shaojuan Geng; Hongwu Zhang; Jingyi Chen; Weiguang Huang

    2007-01-01

    A numerical study of the effect of discrete micro tip injection on unsteady tip clearance flow pattern in an isolated axial compressor rotor is presented, intending to better understand the flow mechanism behind stall control measures that act on tip clearance flow. Under the influence of injection the unsteadiness of self-induced tip clearance flow could be weakened. Also the radial migration of tip clearance vortex is confined to a smaller radial extent near the rotor tip and the trajectory of tip clearance flow is pushed more downstream. So the injection is beneficial to improve compressor stability and increase static pressure rise near rotor tip region. The results of injection with different injected mass flow rates show that for the special type of injector adopted in the paper the effect of injection on tip clearance flow may be different according to the relative strength between these two streams of flow. For a fixed injected mass flow rate, reducing the injector area to increase injection velocity can improve the effect of injection on tip clearance flow and thus the compressor stability. A comparison of calculations between single blade passage and multiple blade passages validates the utility of single passage computations to investigate the tip clearance flow for the case without injection and its interaction with injected flow for the case with tip injection.

  6. Effects of rainfall patterns and land cover on the subsurface flow generation of sloping Ferralsols in southern China.

    Science.gov (United States)

    Duan, Jian; Yang, Jie; Tang, Chongjun; Chen, Lihua; Liu, Yaojun; Wang, Lingyun

    2017-01-01

    Rainfall patterns and land cover are two important factors that affect the runoff generation process. To determine the surface and subsurface flows associated with different rainfall patterns on sloping Ferralsols under different land cover types, observational data related to surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012. The experiment was conducted to assess three land cover types (grass, litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park. During the study period, 114 natural rainfall events produced subsurface flow and were divided into four groups using k-means clustering according to rainfall duration, rainfall depth and maximum 30-min rainfall intensity. The results showed that the total runoff and surface flow values were highest for bare land under all four rainfall patterns and lowest for the covered plots. However, covered plots generated higher subsurface flow values than bare land. Moreover, the surface and subsurface flows associated with the three land cover types differed significantly under different rainfall patterns. Rainfall patterns with low intensities and long durations created more subsurface flow in the grass and litter cover types, whereas rainfall patterns with high intensities and short durations resulted in greater surface flow over bare land. Rainfall pattern I had the highest surface and subsurface flow values for the grass cover and litter cover types. The highest surface flow value and lowest subsurface flow value for bare land occurred under rainfall pattern IV. Rainfall pattern II generated the highest subsurface flow value for bare land. Therefore, grass or litter cover are able to convert more surface flow into subsurface flow under different rainfall patterns. The rainfall patterns studied had greater effects on subsurface flow than on total runoff and surface flow for covered surfaces, as well as a greater effect on surface flows associated

  7. Microbial population dynamics in an anaerobic CSTR treating a chemical synthesis-based pharmaceutical wastewater.

    Science.gov (United States)

    Oz, Nilgun Ayman; Ince, Orhan; Ince, Bahar Kasapgil; Akarsubasi, Alper Tunga; Eyice, Ozge

    2003-01-01

    Effects of a chemical synthesis based pharmaceutical wastewater on performance of an anaerobic completely stirred tank reactor (CSTR), activity of acetoclastic methanogens and microbial composition were evaluated under various influent compositions. Initially, the CSTR was fed with glucose up to an organic loading rate (OLR) of 6 kg COD/m3 x d corresponding to an F/M ratio of 0.43 with a hydraulic retention time (HRT) of 2.5 days. A COD removal efficiency of 92% and a methane yield of 0.32 m3 CH4/kg COD(removed) were achieved whilst specific methanogenic activity (SMA) was found to be 336mL CH4/gTVS x d. After the CSTR was fed with pre-aerated wastewater diluted by glucose in different dilution ratios of 10% (w/v), 30% (w/v), 70% (w/v), and 100% (w/v) pre-aerated wastewater, gradual decreases in COD removal efficiency to 71%, methane yield to 0.28 m3CH4/kg COD(removed) and SMA to 166 mL CH4/gTVS d occurred whilst volatile fatty acid concentration reached to 1474 mg/L. After the raw wastewater diluted with the pre-aerated wastewater was fed into the CSTR in increasing ratios of 10% (w/v), 30% (w/v), and 60% (w/v), there was a proportional deterioration in performance in terms of COD removal efficiency, methane yield and acetoclastic methanogenic activity. Epifluorescence microscopy of the seed sludge revealed that Methanococcus-like species, short, and medium rods were found to be equally dominant. The short and medium rod species remained equally dominant groups in the CSTR throughout the feeding regime whilst Methanococcus-like species and long rods were found to be in insignificant numbers at the end of the study. Changes in archael diversity were determined using molecular analyses such as polymerase chain reaction (PCR), and denaturent gradient gel electrophoresis (DGGE). Results showed that overall archeal diversity did not change much whereas changes in composition of eubacterial population occurred.

  8. 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.

  9. Gap-flow patterns behind twin-cylinders at low Reynolds number

    Energy Technology Data Exchange (ETDEWEB)

    Yen, Shun Chang; Liu, Chien Ting [National Taiwan Ocean University, Keelung (China)

    2011-11-15

    The flow structures, drag coefficients (C{sub d}) and vortex shedding characteristics around a single square cylinder and twin side-by-side square cylinders were experimentally investigated with various Reynolds numbers (Re) and gap ratios (g{sup *}) in a vertical water tunnel. The Reynolds number (Re) and gap ratio (g{sup *}) were 178 < Re < 892 and 0 {<=} g{sup *} {<=} 2.5, respectively. The flow patterns and vortex shedding frequency were determined using the particle tracking flow visualization (PTFV). The flow structures, velocity properties, and drag coefficients were calculated using the particle image velocimetry (PIV). The topological flow patterns of vortex evolution processes were plotted and analyzed based on critical point theory. Furthermore, the flow structures behind twin side-by-side square cylinders were classified into three modes - single vortex-street mode, gap-flow mode and couple vortex-streets mode. The maximum C{sub d} occurred in the single vortex-street mode, and the minimum C{sub d} occurred in the gap-flow mode. The highest Strouhal number (St) occurred in the single vortex-street mode, and the lowest St occurred in the gap-flow mode.

  10. Analyzing Unsatirated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Y.S. Wu; G. Lu; K. Zhang; L. Pan; G.S. Bodvarsson

    2006-08-03

    Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies, because of the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. This paper presents an integrated modeling methodology for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The modeling approach integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for modeling analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations and their results of flow patterns in the unsaturated zone. In particular, this model provides a much clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain's flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.

  11. Effect of air-flow on the evaluation of refractive surgery ablation patterns.

    Science.gov (United States)

    Dorronsoro, Carlos; Schumacher, Silvia; Pérez-Merino, Pablo; Siegel, Jan; Mrochen, Michael; Marcos, Susana

    2011-02-28

    An Allegretto Eye-Q laser platform (Wavelight GmbH, Erlangen, Germany) was used to study the effect of air-flow speed on the ablation of artificial polymer corneas used for testing refractive surgery patterns. Flat samples of two materials (PMMA and Filofocon A) were ablated at four different air flow conditions. The shape and profile of the ablated surfaces were measured with a precise non-contact optical surface profilometer. Significant asymmetries in the measured profiles were found when the ablation was performed with the clinical air aspiration system, and also without air flow. Increasing air-flow produced deeper ablations, improved symmetry, and increased the repeatability of the ablation pattern. Shielding of the laser pulse by the plume of smoke during the ablation of plastic samples reduced the central ablation depth by more than 40% with no-air flow, 30% with clinical air aspiration, and 5% with 1.15 m/s air flow. A simple model based on non-inertial dragging of the particles by air flow predicts no central shielding with 2.3 m/s air flow, and accurately predicts (within 2 μm) the decrease of central ablation depth by shielding. The shielding effects for PMMA and Filofocon A were similar despite the differences in the ablation properties of the materials and the different full-shielding transmission coefficient, which is related to the number of particles ejected and their associated optical behavior. Air flow is a key factor in the evaluation of ablation patterns in refractive surgery using plastic models, as significant shielding effects are found with typical air-flow levels used under clinical conditions. Shielding effects can be avoided by tuning the air flow to the laser repetition rate.

  12. Velocity bias induced by flow patterns around ADCPs and associated deployment platforms

    Science.gov (United States)

    Mueller, David S.

    2015-01-01

    Velocity measurements near the Acoustic Doppler Current Profiler (ADCP) are important for mapping surface currents, measuring velocity and discharge in shallow streams, and providing accurate estimates of discharge in the top unmeasured portion of the water column. Improvements to ADCP performance permit measurement of velocities much closer (5 cm) to the transducer than has been possible in the past (25 cm). Velocity profiles collected by the U.S. Geological Survey (USGS) with a 1200 kHz Rio Grande Zedhead ADCP in 2002 showed a negative bias in measured velocities near the transducers. On the basis of these results, the USGS initiated a study combining field, laboratory, and numerical modeling data to assess the effect of flow patterns caused by flow around the ADCP and deployment platforms on velocities measured near the transducers. This ongoing study has shown that the negative bias observed in the field is due to the flow pattern around the ADCP. The flow pattern around an ADCP violates the basic assumption of flow homogeneity required for an accurate three-dimensional velocity solution. Results, to date (2014), have indicated velocity biases within the measurable profile, due to flow disturbance, for the TRDI 1200 kHz Rio Grande Zedhead and the SonTek RiverSurveyor M9 ADCPs. The flow speed past the ADCP, the mount and the deployment platform have also been shown to play an important role in the magnitude and extent of the velocity bias.

  13. Laminar flow in a microchannel with hydrophobic surface patterned microribs oriented parallel to the flow direction

    Science.gov (United States)

    Maynes, D.; Jeffs, K.; Woolford, B.; Webb, B. W.

    2007-09-01

    This paper reports results of an analytical and experimental investigation of the laminar flow in a parallel-plate microchannel with ultrahydrophobic top and bottom walls. The walls are fabricated with microribs and cavities that are oriented parallel to the flow direction. The channel walls are modeled in an idealized fashion, with the shape of the liquid-vapor meniscus approximated as flat. An analytical model of the vapor cavity flow is employed and coupled with a numerical model of the liquid flow by matching the local liquid and vapor phase velocity and shear stress at the interface. The numerical predictions show that the effective slip length and the reduction in the classical friction factor-Reynolds number product increase with increasing relative cavity width, increasing relative cavity depth, and decreasing relative microrib/cavity module length. Comparisons were also made between the zero shear interface model and the liquid-vapor cavity coupled model. The results illustrate that the zero shear interface model underpredicts the overall flow resistance. Further, the deviation between the two models was found to be significantly larger for increasing values of both the relative rib/cavity module width and the cavity fraction. The trends in the frictional pressure drop predictions are in good agreement with experimental measurements made at similar conditions, with greater deviation observed at increasing size of the cavity fraction. Based on the numerical predictions, an expression is proposed in which the friction factor-Reynolds number product may be estimated in terms of the important variables.

  14. Short-range dynamics and prediction of mesoscale flow patterns in the MISTRAL field experiment

    Energy Technology Data Exchange (ETDEWEB)

    Weber, R.O.; Kaufmann, P.; Talkner, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    In a limited area of about 50 km by 50 km with complex topography, wind measurements on a dense network were performed during the MISTRAL field experiment in 1991-1992. From these data the characteristic wind fields were identified by an automated classification method. The dynamics of the resulting twelve typical regional flow patterns is studied. It is discussed how transitions between the flow patterns take place and how well the transition probabilities can be described in the framework of a Markov model. Guided by this discussion, a variety of prediction models were tested which allow a short-term forecast of the flow pattern type. It is found that a prediction model which uses forecast information from the synoptic scale has the best forecast skill. (author) 2 figs., 7 refs.

  15. Decompositions of injection patterns for nodal flow allocation in renewable electricity networks

    Science.gov (United States)

    Schäfer, Mirko; Tranberg, Bo; Hempel, Sabrina; Schramm, Stefan; Greiner, Martin

    2017-08-01

    The large-scale integration of fluctuating renewable power generation represents a challenge to the technical and economical design of a sustainable future electricity system. In this context, the increasing significance of long-range power transmission calls for innovative methods to understand the emerging complex flow patterns and to integrate price signals about the respective infrastructure needs into the energy market design. We introduce a decomposition method of injection patterns. Contrary to standard flow tracing approaches, it provides nodal allocations of link flows and costs in electricity networks by decomposing the network injection pattern into market-inspired elementary import/export building blocks. We apply the new approach to a simplified data-driven model of a European electricity grid with a high share of renewable wind and solar power generation.

  16. Recognition and tracking of convective flow patterns using Wollaston shearing interferometry

    Science.gov (United States)

    Zaussinger, F.; Krebs, A.; Travnikov, V.; Egbers, Ch.

    2017-09-01

    The GeoFlow experiment on the ISS is designed to study convective flows in a spherical gap under microgravity conditions. The main challenge, however, is the visualization of the fluid flow especially under the safety requirements of the Columbus module. The Wollaston shearing interferometry unit of the Fluid Science Laboratory works by optical means alone and is therefore utilized as measurement device for temperature fluctuations. The resulting interferograms in terms of fringe patterns are the base for the presented advanced post-processing techniques. They are used to identify convective patterns, to track these structures and to reconstruct the inaccessible three-dimensional temperature field. A comparison between experimentally gained results and numerically calculated interferograms is given, too. We show that convective patterns are automatically recognized and tracked accurately in experimental images by means of the generalized structure tensor. Furthermore, generic numerical simulations are used to deduce the internal temperature distribution by comparison with interferograms from the experiment.

  17. Analyzing flow patterns in unsaturated fractured rock of YuccaMountain using an integrated modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson,Gudmundur S.

    2003-11-03

    This paper presents a series of modeling investigations to characterize percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The investigations are conducted using a modeling approach that integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model through model calibration. This integrated modeling approach, based on a dual-continuum formulation, takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. In particular, the model results are examined against different types of field-measured data and used to evaluate different hydrogeological conceptual models and their effects on flow patterns in the unsaturated zone. The objective of this work to provide understanding of percolation patterns and flow behavior through the unsaturated zone, which is a crucial issue in assessing repository performance.

  18. Flow Pattern in a Fluidized Bed with a Non-fluidized Zone

    DEFF Research Database (Denmark)

    Lin, Weigang; Dam-Johansen, Kim; Van den Bleek, Cor. M.

    1997-01-01

    The flow pattern of a fluidized bed with non-fluidized zones is investigated both experimentally and theoretically. Experiments were carried out in such a way that air was introduced only through part of the distributor. The results show a significant amount of air flowing to the zone where no air...... is introduced. However, once the gas velocity exceeds the minimum fluidization velocity in the zone where the air is introduced, the cross-flow hardly changes upon further increase of the gas velocity. A continuity equation and Ergun's equation are used to describe the flow pattern and pressure distribution...... over the bed. Very good agreement between the experimental and calculated results is achieved without any fitting parameter. The results are relevant to the understanding of heat transfer behaviour of a fluidized bed combustor (FBC) that is only partly fluidized to control its load....

  19. Two-phase Flow Patterns in High Temperature Generator of Absorption Chiller / Heater

    Science.gov (United States)

    Furukawa, Masahiro; Kanuma, Hitoshi; Sekoguchi, Kotohiko; Takeishi, Masayuki

    There is a lack of information about vapor-liquid two-phase flow patterns determined using void signals in high temperature generator of absorption chiller/heater. Sensing void fraction has been hampered because lithium bromide aqueous solution of strong alkalinity is employed as working fluid at high temperature and high level of vacuum. New void sensor applicable to such difficult conditions was developed. The void Fractions at 48 locations in a high temperature generator were measured simultaneously in both cooling and heating operations. Analysis of void signals detected reveals that the most violent boiling occurs at the upper part of rear plate of combustion chamber and the first line of vertical tubes located in the flue. The flow patterns are strongly affected by the system pressure difference between the cooling and heating operations: there appear bubbly, slug and froth flows in the cooling operation, but only bubbly flow in the heating operation.

  20. An Active Region Model for Capturing Fractal Flow Patterns inUnsaturated Soils: Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hui-Hai; Zhang, R.; Bodvarsson, Gudmundur S.

    2005-06-11

    Preferential flow commonly observed in unsaturated soils allows rapid movement of solute from the soil surface or vadose zone to the groundwater, bypassing a significant volume of unsaturated soil and increasing the risk of groundwater contamination. A variety of evidence indicates that complex preferential patterns observed from fields are fractals. In this study, we developed a relatively simple active region model to incorporate the fractal flow pattern into the continuum approach. In the model, the flow domain is divided into active and inactive regions. Flow occurs preferentially in the active region (characterized by fractals), and inactive region is simply bypassed. A new constitutive relationship (the portion of the active region as a function of saturation) was derived. The validity of the proposed model is demonstrated by the consistency between field observations and the new constitutive relationship.

  1. Impact of vegetation die-off on spatial flow patterns over a tidal marsh

    Science.gov (United States)

    Temmerman, Stijn; Moonen, Pieter; Schoelynck, Jonas; Govers, Gerard; Bouma, Tjeerd J.

    2012-02-01

    Large-scale die-off of tidal marsh vegetation, caused by global change, is expected to change flow patterns over tidal wetlands, and hence to affect valuable wetland functions such as reduction of shoreline erosion, attenuation of storm surges, and sedimentation in response to sea level rise. This study quantified for the first time the effects of large-scale (4 ha) artificial vegetation removal, as proxy of die-off, on the spatial flow patterns through a tidal marsh channel and over the surrounding marsh platform. After vegetation removal, the flow velocities measured on the platform increased by a factor of 2 to 4, while the channel flow velocities decreased by almost a factor of 3. This was associated with a change in flow directions on the platform, from perpendicular to the channel edges when vegetation was present, to a tendency of more parallel flow to the channel edges when vegetation was absent. Comparison with hydrodynamic model simulations explains that the vegetation-induced friction causes both flow reduction on the vegetated platform and flow acceleration towards the non-vegetated channels. Our findings imply that large-scale vegetation die-off would not only result in decreased platform sedimentation rates, but also in sediment infilling of the channels, which together would lead to further worsening of plant growth conditions and a potentially runaway feedback to permanent vegetation loss.

  2. An Integrated Modeling Analysis of Unsaturated Flow Patterns inFractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson,Gudmundur S.

    2005-03-21

    Characterizing percolation patterns in unsaturated zones hasposed a greater challenge to numerical modeling investigations thancomparable saturated zone studies, because of the heterogeneous nature ofunsaturated media as well as the great number of variables impactingunsaturated zone flow. This paper presents an integrated modelingmethodology for quantitatively characterizing percolation patterns in theunsaturated zone of Yucca Mountain, Nevada, a proposed undergroundrepository site for storing high-level radioactive waste. It takes intoaccount the multiple coupled processes of air, water, heat flow andchemical isotopic transport in Yucca Mountain s highly heterogeneous,unsaturated fractured tuffs. The modeling approach integrates a widevariety of moisture, pneumatic, thermal, and isotopic geochemical fielddata into a comprehensive three-dimensional numerical model for modelinganalyses. Modeling results are examined against different types offield-measured data and then used to evaluate different hydrogeologicalconceptual models and their results of flow patterns in the unsaturatedzone. In particular, this integration model provides a much clearerunderstanding of percolation patterns and flow behavior through theunsaturated zone, both crucial issues in assessing repositoryperformance. The integrated approach for quantifying Yucca Mountain sflow system is also demonstrated to provide a comprehensive modeling toolfor characterizing flow and transport processes in complex subsurfacesystems.

  3. TWO-PHASE FLOW PATTERNS IN A 90° BEND AT MICROGRAVITY

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jianfu; K.S.GABRIEL

    2004-01-01

    Bends are widely used in pipelines carrying single- and two-phase fluids in both ground and space applications. In particular, they play more important role in space applications due to the extreme spatial constraints. In the present study, a set of experimental data of two-phase flow patterns and their transitions in a 90° bend with inner diameter of 12.7 mm and curvature radius of 76.5 mm at microgravity conditions are reported. Gas and liquid superficial velocities are found to range from (1.0 ~ 23.6)m/s for gas and (0.09 ~ 0.5)m/s for liquid, respectively. Three major flow patterns,namely slug, slug-annular transitional, and annular flows, are observed in this study. Focusing on the differences between flow patterns in bends and their counterparts in straight pipes, detailed analyses of their characteristics are made. The transitions between adjoining flow patterns are found to be more or less the same as those in straight pipes, and can be predicted using Weber number models satisfactorily.The reasons for such agreement are carefully examined.

  4. Flow regime patterns and their controlling factors in the Ebro basin (Spain)

    Science.gov (United States)

    Bejarano, M. Dolores; Marchamalo, Miguel; García de Jalón, Diego; González del Tánago, Marta

    2010-05-01

    SummaryNatural intra-annual flow fluctuations vary between rivers, being a determining factor for aquatic insects, fish and riparian communities which are adapted to the habitat conditions and different flows throughout the seasons. Moreover, restoration of seasonal flow patterns plays an important role in achieving good ecological status of rivers, through the preservation and/or recovery of components and processes of natural river ecosystems. In this work we: (a) classify fluvial segments in the Ebro basin (North-Eastern Spain) according to the intra-annual variability of flows under natural conditions using statistical cluster analysis of monthly mean flow data; (b) characterise the resulting flow typologies according to several ecologically important hydrological variables; (c) analyse the relationships between flow regimes of fluvial segments and physical variables from their catchments; and finally (d) predict the most probable natural flow regime using logistic models based on the most determinant physical characteristics. Fifteen natural flow typologies were described in the Ebro basin, which were characterised in terms of flow fluctuation through the year as well as timing, flow ratio and duration of the maximum and minimum flows. Precipitation, biogeography and geology of catchments showed the highest correlations with flow regimes. Basin size, mean elevation and slope were also correlated. The logistic model we developed had a prediction success of 72% in the Ebro basin. The definition of the natural hydrological conditions (to which the biological communities are tailored), even when flow data are not available, is an important support in the management of river ecosystems. It is especially suitable for setting goals in aquatic ecosystem conservation or restoration projects.

  5. Arrays of biomimetic hair flow-sensor dedicated for measuring flow patterns

    NARCIS (Netherlands)

    Dagamseh, A.M.K.; Krijnen, G.J.M.

    2011-01-01

    Next to image sensors, future’s robots will definitely use a variety of sensing mechanisms for navigation and prevention of risks to human life, for example flow-sensor arrays for 3D hydrodynamic reconstruction of the near environment. This paper aims to quantify the possibilities of our artificial

  6. Flow patterns of larval fish: undulatory swimming in the intermediate flow regime

    NARCIS (Netherlands)

    Müller, U.K.; Boogaart, van den J.G.M.; Leeuwen, van J.L.

    2008-01-01

    Fish larvae, like many adult fish, swim by undulating their body. However, their body size and swimming speeds put them in the intermediate flow regime, where viscous and inertial forces both play an important role in the interaction between fish and water. To study the influence of the relatively

  7. Efficient azo dye decolorization in a continuous stirred tank reactor (CSTR) with built-in bioelectrochemical system.

    Science.gov (United States)

    Cui, Min-Hua; Cui, Dan; Gao, Lei; Cheng, Hao-Yi; Wang, Ai-Jie

    2016-10-01

    A continuous stirred tank reactor with built-in bioelectrochemical system (CSTR-BES) was developed for azo dye Alizarin Yellow R (AYR) containing wastewater treatment. The decolorization efficiency (DE) of the CSTR-BES was 97.04±0.06% for 7h with sludge concentration of 3000mg/L and initial AYR concentration of 100mg/L, which was superior to that of the sole CSTR mode (open circuit: 54.87±4.34%) and the sole BES mode (without sludge addition: 91.37±0.44%). The effects of sludge concentration and sodium acetate (NaAc) concentration on azo dye decolorization were investigated. The highest DE of CSTR-BES for 4h was 87.66±2.93% with sludge concentration of 12,000mg/L, NaAc concentration of 2000mg/L and initial AYR concentration of 100mg/L. The results in this study indicated that CSTR-BES could be a practical strategy for upgrading conventional anaerobic facilities against refractory wastewater treatment.

  8. Flow pattern and lift evolution of hydrofoil with control of electro-magnetic forces

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The initial responses and evolutions of the flow pattern and lift coefficient of a hydrofoil under the action of electro-magnetic (Lorentz) force have been studied experimentally and numerically, and trace particle methods are employed for them. With the introduction of BVF (boundary vortex flux), the quantitative relation among Lorentz forces, BVF and lifts is deduced. The influences of flow patterns on the hydrofoil lift coefficient have been discussed based on the BVF distribution, and the flow control mechanism of Lorentz force for a hydrofoil has been elucidated. Our results show that the flow pattern and lift of the hydrofoil vary periodically without any force. However, with the action of streamwise Lorentz forces, the separation point on the hydrofoil surface moves backward with a certain velocity, which makes the flow field steady finally. The streamwise Lorentz force raises the foil lift due to the increase of BVF intensity. On the other hand, Lorentz force also increases the hydrofoil surface pressure, which makes the lift decrease. However, the factor leading to the lift enhancement is determinant, therefore, the Lorentz force on the suction side can increase the lift, and the stronger the Lorentz force, the larger the lift enhancement. Our results also show that the localized Lorentz force can also both suppress the flow separation and increase the hydrofoil lift coefficient, furthermore, the Lorentz force located on the tail acts better than that located on the front.

  9. Parallel patterns determination in solving cyclic flow shop problem with setups

    Directory of Open Access Journals (Sweden)

    Bożejko Wojciech

    2017-06-01

    Full Text Available The subject of this work is the new idea of blocks for the cyclic flow shop problem with setup times, using multiple patterns with different sizes determined for each machine constituting optimal schedule of cities for the traveling salesman problem (TSP. We propose to take advantage of the Intel Xeon Phi parallel computing environment during so-called ’blocks’ determination basing on patterns, in effect significantly improving the quality of obtained results.

  10. Vector projectile imaging: time-resolved dynamic visualization of complex flow patterns.

    Science.gov (United States)

    Yiu, Billy Y S; Lai, Simon S M; Yu, Alfred C H

    2014-09-01

    Achieving non-invasive, accurate and time-resolved imaging of vascular flow with spatiotemporal fluctuations is well acknowledged to be an ongoing challenge. In this article, we present a new ultrasound-based framework called vector projectile imaging (VPI) that can dynamically render complex flow patterns over an imaging view at millisecond time resolution. VPI is founded on three principles: (i) high-frame-rate broad-view data acquisition (based on steered plane wave firings); (ii) flow vector estimation derived from multi-angle Doppler analysis (coupled with data regularization and least-squares fitting); (iii) dynamic visualization of color-encoded vector projectiles (with flow speckles displayed as adjunct). Calibration results indicated that by using three transmit angles and three receive angles (-10°, 0°, +10° for both), VPI can consistently compute flow vectors in a multi-vessel phantom with three tubes positioned at different depths (1.5, 4, 6 cm), oriented at different angles (-10°, 0°, +10°) and of different sizes (dilated diameter: 2.2, 4.4 and 6.3 mm; steady flow rate: 2.5 mL/s). The practical merit of VPI was further illustrated through an anthropomorphic flow phantom investigation that considered both healthy and stenosed carotid bifurcation geometries. For the healthy bifurcation with 1.2-Hz carotid flow pulses, VPI was able to render multi-directional and spatiotemporally varying flow patterns (using a nominal frame rate of 416 fps or 2.4-ms time resolution). In the case of stenosed bifurcations (50% eccentric narrowing), VPI enabled dynamic visualization of flow jet and recirculation zones. These findings suggest that VPI holds promise as a new tool for complex flow analysis.

  11. Evaluation of flow volume and flow patterns in the patent false lumen of chronic aortic dissections using velocity-encoded cine magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Toshihisa; Watanabe, Shigeru; Sakurada, Hideki; Ono, Katsuhiro; Urano, Miharu; Hijikata, Yasuyoshi; Saito, Isao; Masuda, Yoshiaki [Chiba Univ. (Japan). School of Medicine

    2000-10-01

    In 21 patients with chronic aortic dissections and proven patent false lumens, the flow volume and flow patterns in the patent false lumens was evaluated using velocity-encoded cine magnetic resonance imaging (VENC-MRI) and the relationship between the flow characteristics and aortic enlargement was retrospectively examined. Flow patterns in the false lumen were divided into 3 groups: pattern A with primarily antegrade flow (n=6), pattern R with primarily retrograde flow (n=3), and pattern B with bidirectional flow (n=12). In group A, the rate of flow volume in the false lumen compared to the total flow volume in true and false lumens (%TFV) and the average rate of enlargement of the maximum diameter of the dissected aorta per year ({delta}D) were significantly greater than in groups R and B (%TFV: 74.1{+-}0.07 vs 15.2{+-}0.03 vs 11.8{+-}0.04, p<0.01; {delta}D: 3.62{+-}0.82 vs 0 vs 0.58{+-}0.15 mm/year, p<0.05, respectively). There was a significant correlation between %TFV and {delta}D (r=0.79, p<0.0001). Evaluation of flow volume and flow patterns in the patent false lumen using VENC-MRI may be useful for predicting enlargement of the dissected aorta. (author)

  12. Pulmonary vein flow pattern in children with bidirectional cavopulmonary connection or Fontan circuit

    Energy Technology Data Exchange (ETDEWEB)

    Shariat, Masoud; Yoo, Shi-Joon [Hospital for Sick Children, Department of Radiology, Toronto (Canada); Grosse-Wortmann, Lars; Windram, Jonathan [Hospital for Sick Children, Department of Cardiology, Toronto (Canada)

    2012-02-15

    Typical flow velocity profiles in the extraparenchymal pulmonary veins (PVs) demonstrate two major antegrade flow waves: a biphasic systolic wave (S), with S1 and S2 peaks and a monophasic early diastolic wave (D). Flow reversal during atrial systole (A) is common. There is agreement that the forward diastolic PV flow wave is caused by left ventricular relaxation with opening of the mitral valve. The origin of the PV systolic wave, however, remains a topic of debate. Some studies have suggested that the S wave is created by the relaxation of the left atrium and descent of the mitral valve plane. These studies have concluded that forces generated by the right ventricle (RV) have no effect on the S wave. Others suggest that the forward propagation of the right ventricular systolic pressure pulse is the major contributor to the S wave. To determine whether any part of the systolic wave of PV flow is dependent on forces created by the right ventricle. We assessed PV flow pattern, as obtained by cardiac MRI in 12 cases (39 pulmonary veins) with RV-independent pulmonary circulation (bidirectional cavopulmonary connection or Fontan circulation). Phase-contrast imaging of the PVs was performed on a 1.5-T MR scanner with velocity encoding set at 120 cm/s. We compared these flow patterns with those of a control group of ten children (15 pulmonary veins) who had RV-dependent pulmonary circulation and underwent CMR for other indications. In all PVs of children with RV-independent pulmonary circulation the flow curves showed a single systolic peak in early systole (S1) with the S2 peak consistently absent. PV flow pattern in the control group consistently showed distinct early and late systolic peaks. This study supports the concept that S2 is caused by forward propagation of the right ventricular systolic pressure pulse. It also demonstrates that the S1 is independent of the right ventricle. (orig.)

  13. Pulmonary vein flow pattern in children with bidirectional cavopulmonary connection or Fontan circuit.

    Science.gov (United States)

    Shariat, Masoud; Grosse-Wortmann, Lars; Windram, Jonathan; Yoo, Shi-Joon

    2012-02-01

    Typical flow velocity profiles in the extraparenchymal pulmonary veins (PVs) demonstrate two major antegrade flow waves: a biphasic systolic wave (S), with S1 and S2 peaks and a monophasic early diastolic wave (D). Flow reversal during atrial systole (A) is common. There is agreement that the forward diastolic PV flow wave is caused by left ventricular relaxation with opening of the mitral valve. The origin of the PV systolic wave, however, remains a topic of debate. Some studies have suggested that the S wave is created by the relaxation of the left atrium and descent of the mitral valve plane. These studies have concluded that forces generated by the right ventricle (RV) have no effect on the S wave. Others suggest that the forward propagation of the right ventricular systolic pressure pulse is the major contributor to the S wave. To determine whether any part of the systolic wave of PV flow is dependent on forces created by the right ventricle. We assessed PV flow pattern, as obtained by cardiac MRI in 12 cases (39 pulmonary veins) with RV-independent pulmonary circulation (bidirectional cavopulmonary connection or Fontan circulation). Phase-contrast imaging of the PVs was performed on a 1.5-T MR scanner with velocity encoding set at 120 cm/s. We compared these flow patterns with those of a control group of ten children (15 pulmonary veins) who had RV-dependent pulmonary circulation and underwent CMR for other indications. In all PVs of children with RV-independent pulmonary circulation the flow curves showed a single systolic peak in early systole (S1) with the S2 peak consistently absent. PV flow pattern in the control group consistently showed distinct early and late systolic peaks. This study supports the concept that S2 is caused by forward propagation of the right ventricular systolic pressure pulse. It also demonstrates that the S1 is independent of the right ventricle.

  14. Pattern recognition techniques for horizontal and vertically upward multiphase flow measurement

    Science.gov (United States)

    Arubi, Tesi I. M.; Yeung, Hoi

    2012-03-01

    The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves that has led oil companies to develop smaller and marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective solutions of on-line continuous multiphase flow measurement for well testing, production monitoring, production optimisation, process control and automation. The pattern recognition approach for clamp-on multiphase measurement employed in this study provides one means for meeting this need. High speed caesium-137 radioisotope-based densitometers were installed vertically at the top of a 50.8mm and 101.6mm riser as well as horizontally at the riser base in the Cranfield University multiphase flow test facility. A comprehensive experimental campaign comprising flow conditions typical of operating conditions found in the Petroleum Industry was conducted. The application of a single gamma densitometer unit, in conjunction with pattern recognition techniques to determine both the phase volume fractions and velocities to yield the individual phase flow rates of horizontal and vertically upward multiphase flows was investigated. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma counts signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±5% relative error for the two phase airwater flows and ±10% for three phase air-oil-water flows data.

  15. Identification of microfluidic two-phase flow patterns in lab-on-chip devices.

    Science.gov (United States)

    Yang, Zhaochu; Dong, Tao; Halvorsen, Einar

    2014-01-01

    This work describes a capacitive sensor for identification of microfluidic two-phase flow in lab-on-chip devices. With interdigital electrodes and thin insulation layer utilized, this sensor is capable of being integrated with the microsystems easily. Transducing principle and design considerations are presented with respect to the microfluidic gas/liquid flow patterns. Numerical simulation results verify the operational principle. And the factors affecting the performance of the sensor are discussed. Besides, a feasible process flow for the fabrication is also proposed.

  16. Using a 3-dimensional laser anemometer to determine mean streamline patterns in a turbulent flow

    Science.gov (United States)

    Orloff, K. L.; Snyder, P. K.

    1984-01-01

    The determination of mean streamline patterns by moving the test point in the direction of the measured velocity is shown to produce cumulative errors that are unacceptable. A two-dimensional algorithm that minimizes these errors is presented and is analytically validated using simple potential flows. The algorithm is extended to three-dimensional flows and is again validated analytically. Finally, as an example of a typical application of the algorithm, mean streamlines are measured in a complex, turbulent flow with a three-dimensional laser anemometer.

  17. Zonal Flow as Pattern Formation: Merging Jets and the Ultimate Jet Length Scale

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey B. Parker and John A. Krommes

    2013-01-30

    Zonal flows are well known to arise spontaneously out of turbulence. It is shown that for statisti- cally averaged equations of quasigeostrophic turbulence on a beta plane, zonal flows and inhomoge- neous turbulence fit into the framework of pattern formation. There are many implications. First, the zonal flow wavelength is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

  18. Experimental evaluation of streamline patterns and separated flows in a series of branching vessels with implications for atherosclerosis and thrombosis.

    Science.gov (United States)

    el-Masry, O A; Feuerstein, I A; Round, G F

    1978-10-01

    Flow conditions in four models representing the aortic bifurcation, iliac bifuraction, and a renal artery branch were investigated at volumetric flow rates corresponding to Reynolds numbers from 1000 to 4000 over the complete range of flow division between daughter vessels. Qualitative flow streamline patterns and quantitative definition of those flow conditions leading to disturbed flow (flow separation ) were determined primarily at steady flow with a limited set of pulsatie experiments. Under conditions of no flow separation, common characteristic streamline patterns not parallel to the center lines of parent or daughter tubes were found for all models. These effects were accentuated with increasing Reynolds number. Flow separation was inducible through alteration of flow division between daughter vessels or by an increase in flow rate. Each of the four models had distinct combinations of flow division ratio and flow rate which gave: (1) no flow separation, (2) flow separation at the outside of the right daughter tube, and (3) flow separation at the outside of the left daughter tube. Models representing the renal artery also had regions of simultaneous left- and righthand separation on the outside of their daughter tubes. The separated flows observed here displayed streamlines forming an open vortex with flows entering and leaving. These regions, which occur only at distinct combinations of flow rate and flow division, may be key centers where platelet aggregates may form, release constituents, and cause vessel injury.

  19. Modeling of debris flow depositional patterns according to the catchments and sediment source areas characteristics

    Science.gov (United States)

    Tiranti, Davide; Deangeli, Chiara

    2015-03-01

    A method to predict the most probable flow rheology in Alpine debris flows is presented. The methods classifies outcropping rock masses in catchments on the basis of the type of resulting unconsolidated deposits. The grain size distribution of the debris material and the depositional style of past debris flow events are related to the dominant flow processes: viscoplastic and frictional/collisional. Three catchments in the upper Susa Valley (Western Alps), characterized by different lithologies, were selected for numerical analysis carried out with a Cellular Automata code with viscoplastic and frictional/collisional rheologies. The obtained numerical results are in good agreement with in site evidences in terms of depositional patterns, confirming the possibility of choosing the rheology of the debris flow based on the source material within the catchment.

  20. Temporal and spatial evolution characteristics of gas-liquid two-phase flow pattern based on image texture spectrum descriptor

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xi-guo; JIN Ning-de; WANG Zhen-ya; ZHANG Wen-yin

    2009-01-01

    The dynamic image information of typical gas-liquid two-phase flow patterns in vertical upward pipe is captured by a high-speed dynamic camera. The texture spectrum descriptor is used to describe the texture characteristics of the processed images whose content is represented in the form of texture spectrum histogram, and four time-varying characteristic param-eter indexes which represent image texture structure of different flow patterns are extracted. The study results show that the amplitude fluctuation of texture characteristic parameter indexes of bubble flow is lowest and shows very random complex dynamic behavior; the amplitude fluctuation of slug flow is higher and shows intermittent motion behavior between gas slug and liquid slug, and the amplitude fluctuation of churn flow is the highest and shows better periodicity; the amplitude fluctuation of bubble-slug flow is from low to high and oscillating frequence is higher than that of slug flow, and includes the features of both slug flow and bubble flow; the slug-churn flow loses the periodicity of slug flow and churn flow, and the amplitude fluctuation is high. The results indicate that the image texture characteristic parameter indexes of different flow pattern can reflect the flow characteristics of gas-liquid two-phase flow, which provides a new approach to tmderstand the temporal and spatial evolution of flow pattern dynamics.

  1. Experimental and visual study on flow patterns and pressure drops in U-tubes

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva Lima, J. R.

    2011-07-01

    In single- and two-phase flow heat exchangers (in particular 'coils'), besides the straight tubes there are also many singularities, in particular the 180° return bends (also called return bends or U-bends). However, contrary to the literature concerning pressure drops and heat transfer in straight tubes, where many experimental data and predicting methods are available, only a limited number of studies concerning U-bends can be found. Neither reliable experimental data nor proven prediction methods are available. Indeed, flow structure, pressure drop and heat transfer in U-bends are an old unresolved design problem in the heat transfer industry. Thus, the present study aims at providing further insight on two-phase pressure drops and flows patterns in U-bends. Based on a new type of U-bend test section, an extensive experimental study was conducted. The experimental campaign covered five test sections with three internal diameters (7.8, 10.8 and 13.4 mm), five bend diameters (24.8, 31.7, 38.1, 54.8 and 66.1 mm), tested for three orientations (horizontal, vertical upflow and vertical downflow), two fluids (R134a and R410A), two saturation temperatures (5 and 10 °C) and mass velocities ranging from 150 to 1000 kg s{sup -1} m{sup -2}. The flow pattern observations identified were stratified-wavy, slug-stratified-wavy, intermittent, annular, dryout and mist flows. The effects of the U-bend on the flow patterns were also observed. A total of 5655 pressure drop data were measured at seven different locations in the test section ( straight tubes and U-bend) providing a total of almost 40,000 data points. The straight tube data were first used to improve the actual two-phase straight tube model of Moreno-Quibén and Thome. This updated model was then used to developed a two-phase U-bend pressure drop model. Based on a comparison between experimental and predicted values, it is concluded that the new two-phase frictional pressure drop model for U

  2. Fractal regional myocardial blood flows pattern according to metabolism, not vascular anatomy.

    Science.gov (United States)

    Yipintsoi, Tada; Kroll, Keith; Bassingthwaighte, James B

    2016-02-01

    Regional myocardial blood flows are markedly heterogeneous. Fractal analysis shows strong near-neighbor correlation. In experiments to distinguish control by vascular anatomy vs. local vasomotion, coronary flows were increased in open-chest dogs by stimulating myocardial metabolism (catecholamines + atropine) with and without adenosine. During control states mean left ventricular (LV) myocardial blood flows (microspheres) were 0.5-1 ml·g(-1)·min(-1) and increased to 2-3 ml·g(-1)·min(-1) with catecholamine infusion and to ∼4 ml·g(-1)·min(-1) with adenosine (Ado). Flow heterogeneity was similar in all states: relative dispersion (RD = SD/mean) was ∼25%, using LV pieces 0.1-0.2% of total. During catecholamine infusion local flows increased in proportion to the mean flows in 45% of the LV, "tracking" closely (increased proportionately to mean flow), while ∼40% trended toward the mean. Near-neighbor regional flows remained strongly spatially correlated, with fractal dimension D near 1.2 (Hurst coefficient 0.8). The spatial patterns remain similar at varied levels of metabolic stimulation inferring metabolic dominance. In contrast, adenosine vasodilation increased flows eightfold times control while destroying correlation with the control state. The Ado-induced spatial patterns differed from control but were self-consistent, inferring that with full vasodilation the relaxed arterial anatomy dominates the distribution. We conclude that vascular anatomy governs flow distributions during adenosine vasodilation but that metabolic vasoregulation dominates in normal physiological states.

  3. Flow patterns of larval fish: undulatory swimming in the intermediate flow regime.

    Science.gov (United States)

    Müller, Ulrike K; van den Boogaart, Jos G M; van Leeuwen, Johan L

    2008-01-01

    Fish larvae, like many adult fish, swim by undulating their body. However, their body size and swimming speeds put them in the intermediate flow regime, where viscous and inertial forces both play an important role in the interaction between fish and water. To study the influence of the relatively high viscous forces compared with adult fish, we mapped the flow around swimming zebrafish (Danio rerio) larvae using two-dimensional digital particle image velocimetry (2D-DPIV) in the horizontal and transverse plane of the fish. Fish larvae initiate a swimming bout by bending their body into a C shape. During this initial tail-beat cycle, larvae shed two vortex pairs in the horizontal plane of their wake, one during the preparatory and one during the subsequent propulsive stroke. When they swim ;cyclically' (mean swimming speed does not change significantly between tail beats), fish larvae generate a wide drag wake along their head and anterior body. The flow along the posterior body is dominated by the undulating body movements that cause jet flows into the concave bends of the body wave. Patches of elevated vorticity form around the jets, and travel posteriorly along with the body wave, until they are ultimately shed at the tail near the moment of stroke reversal. Behind the larva, two vortex pairs are formed per tail-beat cycle (the tail beating once left-to-right and then right-to-left) in the horizontal plane of the larval wake. By combining transverse and horizontal cross sections of the wake, we inferred that the wake behind a cyclically swimming zebrafish larva contains two diverging rows of vortex rings to the left and right of the mean path of motion, resembling the wake of steadily swimming adult eels. When the fish larva slows down at the end of a swimming bout, it gradually reduces its tail-beat frequency and amplitude, while the separated boundary layer and drag wake of the anterior body extend posteriorly to envelope the entire larva. This drag wake is

  4. Characterization and treatment of Denizli landfill leachate using anaerobic hybrid/aerobic CSTR systems.

    Science.gov (United States)

    Ağdağ, Osman Nuri

    2011-01-01

    Leachate generated in municipal solid waste landfill contains large amounts of organic and inorganic contaminants. In the scope of the study, characterization and anaerobic/aerobic treatability of leachate from Denizli (Turkey) Sanitary Landfill were investigated. Time-based fluctuations in characteristics of leachate were monitored during a one-year period. In characterization study; chemical oxygen demand (COD), biochemical oxygen demand (BOD) dissolved oxygen, temperature, pH, alkalinity, volatile fatty acids, total nitrogen, NH4-N, BOD5/COD ratio, suspended solid, inert COD, anaerobic toxicity assay and heavy metals concentrations in leachate were monitored. Average COD, BOD and NH4-N concentration in leachate were measured as 18034 mg/l, 11504 mg/l and 454 mg/l, respectively. Generally, pollution parameters in leachate were higher in summer and relatively lower in winter due to dilution by precipitation. For treatment of leachate, two different reactors, namely anaerobic hybrid and aerobic completely stirred tank reactor (CSTR) having effective volumes of 17.7 and 10.5 litres, respectively, were used. After 41 days of start-up period, leachate was loaded to hybrid reactor at 10 different organic loading rates (OLRs). OLR was increased by increasing COD concentrations. COD removal efficiency of hybrid reactor was carried out at a maximum of 91%. A percentage of 96% of residual COD was removed in the aerobic reactor. NH4-N removal rate in CSTR was quite high. In addition, high methane content was obtained as 64% in the hybrid reactor. At the end of the study, after 170 operation days, it can be said that the hybrid reactor and CSTR were very effective for leachate treatment.

  5. Anaerobic digestion of paunch in a CSTR for renewable energy production and nutrient mineralization

    Energy Technology Data Exchange (ETDEWEB)

    Nkemka, Valentine Nkongndem; Marchbank, Douglas H.; Hao, Xiying, E-mail: xiying.hao@agr.gc.ca

    2015-09-15

    Highlights: • Anaerobic digestion and nutrient mineralization of paunch in a CSTR. • Low CH{sub 4} yield and high CH{sub 4} productivity was obtained at an OLR of 2.8 g VS L{sup −1} day{sup −1.} • Post-digestion of the digestate resulted in a CH{sub 4} yield of 0.067 L g{sup −1} VS. • Post-digestion is recommended for further digestate stabilization. - Abstract: A laboratory study investigated the anaerobic digestion of paunch in a continuous stirred tank reactor (CSTR) for the recovery of biogas and mineralization of nutrients. At an organic loading rate (OLR) of 2.8 g VS L{sup −1} day{sup −1} with a 30-day hydraulic retention time (HRT), a CH{sub 4} yield of 0.213 L g{sup −1} VS and CH{sub 4} production rate of 0.600 L L{sup −1} day{sup −1} were obtained. Post-anaerobic digestion of the effluent from the CSTR for 30 days at 40 °C recovered 0.067 L g{sup −1} VS as CH{sub 4}, which was 21% of the batch CH{sub 4} potential. Post-digestion of the effluent from the digestate obtained at this OLR is needed to meet the stable effluent criteria. Furthermore, low levels of soluble ions such as K{sup +}, Ca{sup 2+} and Mg{sup 2+} were found in the liquid fraction of the digestate and the remainder could have been retained in the solid digestate fraction. This study demonstrates the potential of biogas production from paunch in providing renewable energy. In addition, recovery of plant nutrients in the digestate is important for a sustainable agricultural system.

  6. Flow pattern, void fraction and pressure drop of two-phase air-water flow in a horizontal circular micro-channel

    Energy Technology Data Exchange (ETDEWEB)

    Saisorn, Sira [Energy Division, The Joint Graduate School of Energy and Environment (JGSEE), King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand); Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical Engineering, King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

    2008-01-15

    Adiabatic two-phase air-water flow characteristics, including the two-phase flow pattern as well as the void fraction and two-phase frictional pressure drop, in a circular micro-channel are experimentally studied. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The test runs are done at superficial velocity of gas and liquid ranging between 0.37-16 and 0.005-3.04 m/s, respectively. The flow pattern map is developed from the observed flow patterns i.e. slug flow, throat-annular flow, churn flow and annular-rivulet flow. The flow pattern map is compared with those of other researchers obtained from different working fluids. The present single-phase experiments also show that there are no significant differences in the data from the use of air or nitrogen gas, and water or de-ionized water. The void fraction data obtained by image analysis tends to correspond with the homogeneous flow model. The two-phase pressure drops are also used to calculate the frictional multiplier. The multiplier data show a dependence on flow pattern as well as mass flux. A new correlation of two-phase frictional multiplier is also proposed for practical application. (author)

  7. The shock-vortex interaction patterns affected by vortex flow regime and vortex models

    Science.gov (United States)

    Chang, Keun-Shik; Barik, Hrushikesh; Chang, Se-Myong

    2009-08-01

    We have used a third-order essentially non-oscillatory method to obtain numerical shadowgraphs for investigation of shock-vortex interaction patterns. To search different interaction patterns, we have tested two vortex models (the composite vortex model and the Taylor vortex model) and as many as 47 parametric data sets. By shock-vortex interaction, the impinging shock is deformed to a S-shape with leading and lagging parts of the shock. The vortex flow is locally accelerated by the leading shock and locally decelerated by the lagging shock, having a severely elongated vortex core with two vertices. When the leading shock escapes the vortex, implosion effect creates a high pressure in the vertex area where the flow had been most expanded. This compressed region spreads in time with two frontal waves, an induced expansion wave and an induced compression wave. They are subsonic waves when the shock-vortex interaction is weak but become supersonic waves for strong interactions. Under a intermediate interaction, however, an induced shock wave is first developed where flow speed is supersonic but is dissipated where the incoming flow is subsonic. We have identified three different interaction patterns that depend on the vortex flow regime characterized by the shock-vortex interaction.

  8. Circular flow patterns induced by ciliary activity in reconstituted human bronchial epithelium

    Science.gov (United States)

    Viallat, Annie; Khelloufi, Kamel; Gras, Delphine; Chanez, Pascal; Aix Marseille Univ., CNRS, CINaM, Marseille, France Team; Aix Marseille Univ., CNRS, Inserm, LAI, Marseille, France Team

    2016-11-01

    Mucociliary clearance is the transport at the surface of airways of a complex fluid layer, the mucus, moved by the beats of microscopic cilia present on epithelial ciliated cells. We explored the coupling between the spatial organisation and the activity of cilia and the transport of surface fluids on reconstituted cultures of human bronchial epithelium at air-liquid interface, obtained by human biopsies. We reveal the existence of stable local circular surface flow patterns of mucus or Newtonian fluid at the epithelium surface. We find a power law over more than 3 orders of magnitude showing that the average ciliated cell density controls the size of these flow patterns, and, therefore the distance over which mucus can be transported. We show that these circular flow patterns result from the radial linear increase of the local propelling forces (due to ciliary beats) on each flow domain. This linear increase of local forces is induced by a fine self-regulation of both cilia density and orientation of ciliary beats. Local flow domains grow and merge during ciliogenesis to provide macroscopic mucus transport. This is possible only when the viscoelastic mucus continuously exerts a shear stress on beating cilia, revealing a mechanosensitive function of cilia. M. K. Khelloufi thanks the society MedBioMed for financial support. This work was supported by the ANR MUCOCIL project, Grant ANR-13-BSV5-0015 of the French Agence Nationale de la Recherche.

  9. ENVIRONMENTAL AND PROCESS PARAMETERS OF METHANE FERMENTATION IN CONTINUOSLY STIRRED TANK REACTOR (CSTR

    Directory of Open Access Journals (Sweden)

    Kamil Kozłowski

    2016-12-01

    Full Text Available A key indicator of methane fermentation process which influences the cost-effectiveness of the biogas plant is efficient production of methane per 1 m3 of reactor. It depends on the proper selection of environmental and process parameters. This article present collected and analyzed the effect of the most important parameters of continuous methane fermentation (CSTR, which include temperature, pH, nutrient content and the C/N ratio in the feed medium, the presence of inhibitors, and the volume load of reactor, retention time and mixing of digestion reactor. Still, the impact of many factors remain unknown, hence there is a need for more comprehensive studies.

  10. Persistence in a single species CSTR model with suspended flocs and wall attached biofilms.

    Science.gov (United States)

    Mašić, Alma; Eberl, Hermann J

    2012-04-01

    We consider a mathematical model for a bacterial population in a continuously stirred tank reactor (CSTR) with wall attachment. This is a modification of the Freter model, in which we model the sessile bacteria as a microbial biofilm. Our analysis indicates that the results of the algebraically simpler original Freter model largely carry over. In a computational simulation study, we find that the vast majority of bacteria in the reactor will eventually be sessile. However, we also find that suspended biomass is relatively more efficient in removing substrate from the reactor than biofilm bacteria.

  11. Computational multiple steady states for enzymatic esterification of ethanol and oleic acid in an isothermal CSTR.

    Science.gov (United States)

    Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya

    2005-05-01

    The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.

  12. Ethanol production by a flocculant yeast strain in a CSTR type fermentor with cell recycling.

    Science.gov (United States)

    Hojo, O; Hokka, C O; Major, A M

    1999-01-01

    Tests were performed in a continuous stirred tank reactor (CSTR), with and without cell recycling, to produce ethanol. The reactor without cell recycling produced the kinetic model of ethanol production, whereas the reactor with cell recycling allowed for a study of process stability. The Levenspiel kinetic model was adopted; however, in the case of fermentation with cell recycling, the coefficient of cell death was added. It was observed that cellular viability varied greatly throughout the fermenting process and that microaeration is of fundamental importance in maintaining the stability of the process.

  13. Laminar-turbulent patterning in wall-bounded shear flows: a Galerkin model

    CERN Document Server

    Seshasayanan, K

    2015-01-01

    On its way to turbulence, plane Couette flow - the flow between counter-translating parallel plates - displays a puzzling steady oblique laminar-turbulent pattern. We approach this problem via Galerkin modelling of the Navier-Stokes equations. The wall-normal dependence of the hydrodynamic field is treated by means of expansions on functional bases fitting the boundary conditions exactly. This yields a set of partial differential equations for the spatiotemporal dynamics in the plane of the flow. Truncating this set beyond lowest nontrivial order is numerically shown to produce the expected pattern, therefore improving over what was obtained at cruder effective wall-normal resolution. Perspectives opened by the approach are discussed.

  14. Speed dependent stochasticity capacitates Newell model for synchronized flow and oscillation growth pattern

    CERN Document Server

    Tian, Junfang; Jia, Bin; Ma, Shoufeng; Gao, Ziyou

    2016-01-01

    This paper has incorporated the stochasticity into the Newell car following model. Three stochastic driving factors have been considered: (i) Driver's acceleration is stochastic and bounded. (ii) Driver's deceleration includes stochastic component, which is depicted by a deceleration with the randomization probability that is assumed to increase with the speed. (iii) Vehicles in the jam state have a larger randomization probability. Two simulation scenarios are conducted to test the model. In the first scenario, traffic flow on a circular road is investigated, and the empirical characteristics of the synchronized traffic flow can be simulated. In the second scenario, traffic flow pattern induced by a rubberneck bottleneck is studied, and the simulated traffic oscillations are consistent with that in the NGSIM data. Moreover, two experiments of model calibration and validation are conducted. The first is to calibrate and validate using experimental data, which illustrates that the concave growth pattern has be...

  15. Flow patterns of natural convection in an air-filled vertical cavity

    Science.gov (United States)

    Wakitani, Shunichi

    1998-08-01

    Flow patterns of two-dimensional natural convection in a vertical air-filled tall cavity with differentially heated sidewalls are investigated. Numerical simulations based on a finite difference method are carried out for a wide range of Rayleigh numbers and aspect ratios from the onset of the steady multicellular flow, through the reverse transition to the unicellular pattern, to the unsteady multicellular flow. For aspect ratios (height/width) from 10 to 24, the various cellular structures characterized by the number of secondary cells are clarified from the simulations by means of gradually increasing Rayleigh number to 106. Unsteady multicellular solutions are found in some region of Rayleigh numbers less than those at which the reverse transition has occurred.

  16. Fractal flow patterns in hydrophobic microfluidic pore networks: experimental modeling of two-phase flow in porous electrodes

    CERN Document Server

    Berejnov, Viatcheslav; Sinton, David; Djilali, Ned

    2009-01-01

    Experimental two-phase invasion percolation flow patterns were observed in hydrophobic micro-porous networks designed to model fuel cell specific porous media. In order to mimic the operational conditions encountered in the porous electrodes of polymer electrolyte membrane fuel cells (PEMFCs), micro-porous networks were fabricated with corresponding microchannel size distributions. The inlet channels were invaded homogeneously with flow rates corresponding to fuel cell current densities of 1.0 to 0.1 A/cm2 (Ca 10e-7-10e-8). A variety of fractal breakthrough patterns were observed and analyzed to quantify flooding density and geometrical diversity in terms of the total saturation, St, local saturations, s, and fractal dimension, D. It was found that St increases monotonically during the invasion process until the breakthrough point is reached, and s profiles indicate the dynamic distribution of the liquid phase during the process. Fractal analysis confirmed that the experiments fall within the flow regime of i...

  17. Anaerobic co-digestion of waste activated sludge and greasy sludge from flotation process: batch versus CSTR experiments to investigate optimal design.

    Science.gov (United States)

    Girault, R; Bridoux, G; Nauleau, F; Poullain, C; Buffet, J; Peu, P; Sadowski, A G; Béline, F

    2012-02-01

    In this study, the maximum ratio of greasy sludge to incorporate with waste activated sludge was investigated in batch and CSTR experiments. In batch experiments, inhibition occurred with a greasy sludge ratio of more than 20-30% of the feed COD. In CSTR experiments, the optimal greasy sludge ratio was 60% of the feed COD and inhibition occurred above a ratio of 80%. Hence, batch experiments can predict the CSTR yield when the degradation phenomenon are additive but cannot be used to determine the maximum ratio to be used in a CSTR configuration. Additionally, when the ratio of greasy sludge increased from 0% to 60% of the feed COD, CSTR methane production increased by more than 60%. When the greasy sludge ratio increased from 60% to 90% of the feed COD, the reactor yield decreased by 75%.

  18. Flow Pattern Analysis and Performance Improvement of Regenerative Flow Pump Using Blade Geometry Modification

    Directory of Open Access Journals (Sweden)

    J. Nejadrajabali

    2016-01-01

    Full Text Available Regenerative pump is a low specific speed and rotor-dynamic turbomachine capable of developing high heads at low flow rates. In this paper, a numerical study has been carried out in order to investigate the effect of blade angle on the performance of a regenerative pump. Two groups of impellers were employed. The first type has symmetric angle blades with identical inlet/outlet angles of ±10°, ±30°, and ±50° and the second group has nonsymmetric angle blades in which the inlet angle was set to 0° and six different angles of ±10°, ±30°, and ±50° were designed for the outlet of the blades. A total of 12 impellers, as well as primary radial blades impeller, were investigated in this study. The results showed that all forward blades have higher head coefficients than radial blades impeller at design flow coefficient. It was found that regenerative pumps with symmetric angle forward blades have better performance than other types. Also, it is worth mentioning that the highest head coefficient and efficiency occur at angle +10<β<+30 of symmetric angle blades. It was found that the maximum efficiency occurs at angle of +15.5° by curve fitting to the data obtained from numerical simulations for symmetric angle forward blades.

  19. Streaming driven by sessile microbubbles: Explaining flow patterns and frequency response

    Science.gov (United States)

    Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

    2013-11-01

    Ultrasound excitation of bubbles drives powerful steady streaming flows which have found widespread applications in microfluidics, where bubbles are typically of semicircular cross section and attached to walls of the device (sessile). While bubble-driven streaming in bulk fluid is well understood, this practically relevant case presents additional complexity introduced by the wall and contact lines. We develop an asymptotic theory that takes into account the presence of the wall as well as the oscillation dynamics of the bubble, providing a complete description of the streaming flow as a function only of the driving frequency, the bubble size, and the physical properties of the fluid. We show that the coupling between different bubble oscillation modes sustains the experimentally observed streaming flow vortex pattern over a broad range of frequencies, greatly exceeding the widths of individual mode resonances. Above a threshold frequency, we predict, and observe in experiment, reversal of the flow direction. Our analytical theory can be used to guide the design of microfluidic devices, both in situations where robust flow patterns insensitive to parameter changes are desired (e.g. lab-on-a-chip sorters), and in cases where intentional modulation of the flow field appearance is key (e.g. efficient mixers). Current address: Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology.

  20. An artificial intelligence based improved classification of two-phase flow patterns with feature extracted from acquired images.

    Science.gov (United States)

    Shanthi, C; Pappa, N

    2017-05-01

    Flow pattern recognition is necessary to select design equations for finding operating details of the process and to perform computational simulations. Visual image processing can be used to automate the interpretation of patterns in two-phase flow. In this paper, an attempt has been made to improve the classification accuracy of the flow pattern of gas/ liquid two- phase flow using fuzzy logic and Support Vector Machine (SVM) with Principal Component Analysis (PCA). The videos of six different types of flow patterns namely, annular flow, bubble flow, churn flow, plug flow, slug flow and stratified flow are recorded for a period and converted to 2D images for processing. The textural and shape features extracted using image processing are applied as inputs to various classification schemes namely fuzzy logic, SVM and SVM with PCA in order to identify the type of flow pattern. The results obtained are compared and it is observed that SVM with features reduced using PCA gives the better classification accuracy and computationally less intensive than other two existing schemes. This study results cover industrial application needs including oil and gas and any other gas-liquid two-phase flows. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Dichotomous-noise-induced pattern formation in a reaction-diffusion system

    Science.gov (United States)

    Das, Debojyoti; Ray, Deb Shankar

    2013-06-01

    We consider a generic reaction-diffusion system in which one of the parameters is subjected to dichotomous noise by controlling the flow of one of the reacting species in a continuous-flow-stirred-tank reactor (CSTR) -membrane reactor. The linear stability analysis in an extended phase space is carried out by invoking Furutzu-Novikov procedure for exponentially correlated multiplicative noise to derive the instability condition in the plane of the noise parameters (correlation time and strength of the noise). We demonstrate that depending on the correlation time an optimal strength of noise governs the self-organization. Our theoretical analysis is corroborated by numerical simulations on pattern formation in a chlorine-dioxide-iodine-malonic acid reaction-diffusion system.

  2. Dual-RiverSonde measurements of two-dimensional river flow patterns

    Science.gov (United States)

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.; Stumpner, P.; Burau, J.R.

    2008-01-01

    Two-dimensional river flow patterns have been measured using a pair of RiverSondes in two experiments in the Sacramento-San Joaquin River Delta system of central California during April and October 2007. An experiment was conducted at Walnut Grove, California in order to explore the use of dual RiverSondes to measure flow patterns at a location which is important in the study of juvenile fish migration. The data available during the first experiment were limited by low wind, so a second experiment was conducted at Threemile Slough where wind conditions and surface turbulence historically have resulted in abundant data. Both experiments included ADCP near-surface velocity measurements from either manned or unmanned boats. Both experiments showed good comparisons between the RiverSonde and ADCP measurements. The flow conditions at both locations are dominated by tidal effects, with partial flow reversal at Walnut Grove and complete flow reversal at Threemile Slough. Both systems showed complex flow patterns during the flow reversals. Quantitative comparisons between the RiverSondes and an ADCP on a manned boat at Walnut Grove showed mean differences of 4.5 cm/s in the u (eastward) and 7.6 cm/s in the v (northward) components, and RMS differences of 14.7 cm/s in the u component and 21.0 cm/s in the v component. Quantitative comparisons between the RiverSondes and ADCPs on autonomous survey vessels at Threemile Slough showed mean differences of 0.007 cm/s in the u component and 0.5 cm/s in the v component, and RMS differences of 7.9 cm/s in the u component and 13.5 cm/s in the v component after obvious outliers were removed. ?? 2008 IEEE.

  3. Visualized study on specific points on demand curves and flow patterns in a single-side heated narrow rectangular channel

    Energy Technology Data Exchange (ETDEWEB)

    Wang Junfeng [CNNC Key Laboratory on Reactor Thermo-Hydraulics Technology, Nuclear Power Institute of China, Chengdu, Sichuan (China); Huang Yanping, E-mail: hypgroup@163.com [CNNC Key Laboratory on Reactor Thermo-Hydraulics Technology, Nuclear Power Institute of China, Chengdu, Sichuan (China); Wang Yanlin [CNNC Key Laboratory on Reactor Thermo-Hydraulics Technology, Nuclear Power Institute of China, Chengdu, Sichuan (China)

    2011-10-15

    Highlights: > Specific points on the demand curve and flow patterns are visually studied. > Bubbly, churn, and annular flows were observed. > Onset of flow instability and bubbly-churn transition occurs at the same time. > The evolution of specific points and flow pattern transitions were examined. - Abstract: A simultaneous visualization and measurement study on some specific points on demand curves, such as onset of nucleate boiling (ONB), onset of significant void (OSV), onset of flow instability (OFI), and two-phase flow patterns in a single-side heated narrow rectangular channel, having a width of 40 mm and a gap of 3 mm, was carried out. New experimental approaches were adopted to identify OSV and OFI in a narrow rectangular channel. Under experimental conditions, the ONB could be predicted well by the Sato and Matsumura model. The OSV model of Bowring can reasonably predict the OSV if the single-side heated condition is considered. The OFI was close to the saturated boiling point and could be described accurately by Kennedy's correlation. The two-phase flow patterns observed in this experiment could be classified into bubbly, churn, and annular flow. Slug flow was never observed. The OFI always occurred when the bubbles at the channel exit began to coalesce, which corresponded to the beginning of the bubbly-churn transition in flow patterns. Finally, the evolution of specific points and flow pattern transitions were examined in a single-side heated narrow rectangular channel.

  4. The Hall current system revealed as a statistical significant pattern during fast flows

    Directory of Open Access Journals (Sweden)

    K. Snekvik

    2008-11-01

    Full Text Available We have examined the dawn-dusk component of the magnetic field, BY, in the night side current sheet during fast flows in the neutral sheet. 237 h of Cluster data from the plasma sheet between 2 August 2002 and 2 October 2002 have been analysed. The spatial pattern of BY as a function of the distance from the centre of the current sheet has been estimated by using a Harris current sheet model. We have used the average slopes of these patterns to estimate earthward and tailward currents. For earthward fast flows there is a tailward current in the inner central plasma sheet and an earthward current in the outer central plasma sheet on average. For tailward fast flows the currents are oppositely directed. These observations are interpreted as signatures of Hall currents in the reconnection region or as field aligned currents which are connected with these currents. Although fast flows often are associated with a dawn-dusk current wedge, we believe that we have managed to filter out such currents from our statistical patterns.

  5. 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.

  6. Cryptic species? Patterns of maternal and paternal gene flow in eight neotropical bats.

    Directory of Open Access Journals (Sweden)

    Elizabeth L Clare

    Full Text Available Levels of sequence divergence at mitochondrial loci are frequently used in phylogeographic analysis and species delimitation though single marker systems cannot assess bi-parental gene flow. In this investigation I compare the phylogeographic patterns revealed through the maternally inherited mitochondrial COI region and the paternally inherited 7(th intron region of the Dby gene on the Y-chromosome in eight common Neotropical bat species. These species are diverse and include members of two families from the feeding guilds of sanguivores, nectarivores, frugivores, carnivores and insectivores. In each case, the currently recognized taxon is comprised of distinct, substantially divergent intraspecific mitochondrial lineages suggesting cryptic species complexes. In Chrotopterus auritus, and Saccopteryx bilineata I observed congruent patterns of divergence in both genetic regions suggesting a cessation of gene flow between intraspecific groups. This evidence supports the existence of cryptic species complexes which meet the criteria of the genetic species concept. In Glossophaga soricina two intraspecific groups with largely sympatric South American ranges show evidence for incomplete lineage sorting or frequent hybridization while a third group with a Central American distribution appears to diverge congruently at both loci suggesting speciation. Within Desmodus rotundus and Trachops cirrhosus the paternally inherited region was monomorphic and thus does not support or refute the potential for cryptic speciation. In Uroderma bilobatum, Micronycteris megalotis and Platyrrhinus helleri the gene regions show conflicting patterns of divergence and I cannot exclude ongoing gene flow between intraspecific groups. This analysis provides a comprehensive comparison across taxa and employs both maternally and paternally inherited gene regions to validate patterns of gene flow. I present evidence for previously unrecognized species meeting the criteria of

  7. Bead-flow pattern: quantitation of fluid movement during torsional and longitudinal phacoemulsification.

    Science.gov (United States)

    de Castro, Luis E Fernández; Dimalanta, Ramon C; Solomon, Kerry D

    2010-06-01

    To develop a bead-flow pattern for visualizing and comparatively quantifying fluid movement using a torsional or longitudinal ultrasound (US) phaco handpiece. Magill Laser Center, Medical University of South Carolina, Charleston, South Carolina, USA. Visualization and quantification of intraocular fluid dynamics were evaluated by injecting neutrally buoyant, collagen-coated polystyrene beads (diameter, 125 to 212 microm) into the phacoemulsification irrigation flow. Using the anterior chamber of a cadaver or porcine eye or a laboratory test chamber, the bead-flow pattern was video recorded. Qualitative comparisons between longitudinal and torsional phacoemulsification were made using video-processing software to track the beads frame by frame. The time (quantitative) required to aspirate a bolus of beads from the anterior chamber (clearance time) was measured and compared between the 2 modalities. Aspiration efficiency was calculated to compare operating conditions in a test chamber using high-speed videography; conditions included irrigation/aspiration (I/A) only (0% power) and clinically relevant fluidic parameters and power modulations with torsional, longitudinal, or a combination of powers applied. Qualitative and quantitative analyses of the fluidic patterns of bead flow in the peripheral anterior chamber and near the aspirating tip opening indicated that torsional fluidics behave closer to the I/A-only configuration than longitudinal phacoemulsification, with the latter repelling more bead material in front of the aspiration tip. Bead clearance time was approximately 50% faster with torsional than with longitudinal US, regardless of the power setting. Bead flow-pattern evaluation is a feasible approach to future studies of fluid movement in the anterior chamber. (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  8. Classification of pulmonary system diseases patterns using flow-volume curve.

    Science.gov (United States)

    Arabalibeik, Hossein; Jafari, Samaneh; Agin, Khosro

    2011-01-01

    Spirometry is the most common pulmonary function test. It provides useful information for early detection of respiratory system abnormalities. While decision support systems use normally calculated parameters such as FEV1, FVC, and FEV1% to diagnose the pattern of respiratory system diseases, expert physicians pay close attention to the pattern of the flow-volume curve as well. Fisher discriminant analysis shows that coefficients of a simple polynomial function fitted to the curve, can capture the information about the disease patterns much better than the familiar single point parameters. A neural network then can classify the abnormality pattern as restrictive, obstructive, mixed, or normal. Using the data from 205 adult volunteers, total accuracy, sensitivity and specificity for four categories are 97.6%, 97.5% and 98.8% respectively.

  9. Anaerobic monodigestion of poultry manure: determination of operational parameters for CSTR.

    Science.gov (United States)

    Chamy, R; León, C; Vivanco, E; Poirrier, P; Ramos, C

    2012-01-01

    In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.

  10. Comparative study of phenol and cyanide containing wastewater in CSTR and SBR activated sludge reactors.

    Science.gov (United States)

    Papadimitriou, C A; Samaras, P; Sakellaropoulos, G P

    2009-01-01

    The objectives of this work were the examination of the performance of two bench scale activated sludge systems, a conventional Continuous Stirring Tank Reactor (CSTR) and a Sequential Batch Reactor (SBR), for the treatment of wastewaters containing phenol and cyanides and the assessment of the toxicity reduction potential by bioassays. The operation of the reactors was monitored by physicochemical analyses, while detoxification potential of the systems was monitored by two bioassays, the marine photobacterium Vibrio fischeri and the ciliate protozoan Tetrahymena thermophila. The reactors influent was highly toxic to both organisms, while activated sludge treatment resulted in the reduction of toxicity of the influent. An increased toxicity removal was observed in the SBR; however CSTR system presented a lower ability for toxicity reduction of influent. The performance of both systems was enhanced by the addition of powdered activated carbon in the aeration tank; activated carbon upgraded the performance of the systems due to the simultaneous biological removal of pollutants and to carbon adsorption process; almost negligible values of phenol and cyanides were measured in the effluents, while further toxicity reduction was observed in both systems.

  11. Experimental study of lactose hydrolysis and separation in cstr-uf membrane reactor

    Directory of Open Access Journals (Sweden)

    M. Namvar-Mahboub

    2012-09-01

    Full Text Available In this study, the effect of processing conditions on the performance of continuous stirred tank -ultrafiltration (CSTR-UF in dead - end mode was investigated. An UF membrane with a molecular weight cutoff of 3 kDa made of regenerated cellulose material was used to separate enzyme from products. The effect of operating pressure ranging between 2 and 5 bar and time on the performance of the CSTR-UF system was studied. The experiments were performed with a 0.139 molar aqueous solution of lactose as feed. According to the experimental data, the lactose concentration in the permeate decreased with time due to concentration polarization and hydrolysis. It was found that the rejection factor of lactose increases from 33 to 77% with time from 5 to 85 min. Permeation flux of the membrane was evaluated in terms of pure water flux (PWF and lactose aqueous solution. Results showed that a high operating pressure led to a high permeation flux for both mentioned cases. Also, adding lactose and enzyme to pure water caused a reduction of the permeation flux due to concentration polarization.

  12. Anaerobic digestion of paunch in a CSTR for renewable energy production and nutrient mineralization.

    Science.gov (United States)

    Nkemka, Valentine Nkongndem; Marchbank, Douglas H; Hao, Xiying

    2015-09-01

    A laboratory study investigated the anaerobic digestion of paunch in a continuous stirred tank reactor (CSTR) for the recovery of biogas and mineralization of nutrients. At an organic loading rate (OLR) of 2.8gVSL(-1)day(-1) with a 30-day hydraulic retention time (HRT), a CH4 yield of 0.213Lg(-1)VS and CH4 production rate of 0.600LL(-1)day(-1) were obtained. Post-anaerobic digestion of the effluent from the CSTR for 30days at 40°C recovered 0.067Lg(-1)VS as CH4, which was 21% of the batch CH4 potential. Post-digestion of the effluent from the digestate obtained at this OLR is needed to meet the stable effluent criteria. Furthermore, low levels of soluble ions such as K(+), Ca(2+) and Mg(2+) were found in the liquid fraction of the digestate and the remainder could have been retained in the solid digestate fraction. This study demonstrates the potential of biogas production from paunch in providing renewable energy. In addition, recovery of plant nutrients in the digestate is important for a sustainable agricultural system.

  13. Spatial and temporal patterns of debris flow deposition in the Oregon Coast Range, USA

    Science.gov (United States)

    May, Christine L.; Gresswell, Robert E.

    2004-01-01

    Patterns of debris-flow occurrence were investigated in 125 headwater basins in the Oregon Coast Range. Time since the previous debris-flows was established using dendrochronology, and recurrence interval estimates ranged from 98 to 357 years. Tributary basins with larger drainage areas had a greater abundance of potential landslide source areas and a greater frequency of scouring events compared to smaller basins. The flux rate of material delivered to the confluence with a larger river influenced the development of small-scale debris-flow fans. Fans at the mouths of tributary basins with smaller drainage areas had a higher likelihood of being eroded by the mainstem river in the interval between debris-flows, compared to bigger basins that had larger, more persistent fans. Valley floor width of the receiving channel also influenced fan development because it limited the space available to accommodate fan formation. Of 63 recent debris-flows, 52% delivered sediment and wood directly to the mainstem river, 30% were deposited on an existing fan before reaching the mainstem, and 18% were deposited within the confines of the tributary valley before reaching the confluence. Spatial variation in the location of past and present depositional surfaces indicated that sequential debris-flow deposits did not consistently form in the same place. Instead of being spatially deterministic, results of this study suggest that temporally variable and stochastic factors may be important for predicting the runout length of debris-flows.

  14. Assessment of the debris-flow susceptibility in tropical mountains using clast distribution patterns

    Science.gov (United States)

    de Carvalho Faria Lima Lopes, Laís; de Almeida Prado Bacellar, Luís; Amorim Castro, Paulo de Tarso

    2016-12-01

    Channel morphometric parameters and clast distribution patterns in selected basins of the Ferriferous Quadrangle tropical mountains, Brazil, were analyzed in order to assess susceptibility to debris flows. Median bed surface clast size (D50) in the main stream channel of these basins shows a coarsening downstream trend with drainage areas of up to 6 km2, which is attributed to debris flow dominated-channels by some authors. The composition and roundness of the bed load, clast sand, and the presence of allochthonous large boulders throughout the channels also suggest the occurrence of past debris flow in the region. Luminescence Optically Stimulated (LOE) dating points out that debris flow could have occurred as a consequence of climate changes in the Late Pleistocene and Holocene and it can now be triggered by deforestation or extreme rainfall events. There has not been any record of past debris flow in the study area, or in other mountainous regions of Brazil where debris flows have recently occurred. Thus, the adopted approach can be useful to assess debris flow susceptibility in this and other similar areas.

  15. Flow pattern and lift evolution of hydrofoil with control of electro-magnetic forces

    Institute of Scientific and Technical Information of China (English)

    CHEN YaoHui; FAN BaoChun; CHEN ZhiHua; LI HongZhi

    2009-01-01

    The Initial responses and evolutions of the flow pattern and lift coefficient of a hydrofoil under the ac-tion of electro-magnetic (Lorentz) force have been studied experimentally and numerically,and trace particle methods are employed for them.With the introduction of BVF (boundary vortex flux),the quantitative relation among Lorentz forces,BVF and lifts is deduced.The influences of flow patterns on the hydrofoil lift coefficient have been discussed based on the BVF distribution,and the flow control mechanism of Lorentz force for a hydrofoil has been elucidated.Our results show that the flow pattern and lift of the hydrofoil vary periodically without any force.However,with the action of streamwise Lorentz forces,the separation point on the hydrofoil surface moves backward with a certain velocity,which makes the flow field steady finally.The streamwise Lorentz force raises the foil lift due to the Increase of BVF intensity.On the other hand,Lorentz force also increases the hydrofoil surface pres-sure,which makes the lift decrease.However,the factor leading to the lift enhancement is determinant,therefore,the Lorentz force on the suction side can increase the lift,and the stronger the Lorentz force,the larger the lift enhancement.Our results also show that the localized Lorentz force can also both suppress the flow separation and increase the hydrofoil lift coefficient,furthermore,the Lorentz force located on the tail acts better than that located on the front.

  16. The impact of traffic-flow patterns on air quality in urban street canyons.

    Science.gov (United States)

    Thaker, Prashant; Gokhale, Sharad

    2016-01-01

    We investigated the effect of different urban traffic-flow patterns on pollutant dispersion in different winds in a real asymmetric street canyon. Free-flow traffic causes more turbulence in the canyon facilitating more dispersion and a reduction in pedestrian level concentration. The comparison of with and without a vehicle-induced-turbulence revealed that when winds were perpendicular, the free-flow traffic reduced the concentration by 73% on the windward side with a minor increase of 17% on the leeward side, whereas for parallel winds, it reduced the concentration by 51% and 29%. The congested-flow traffic increased the concentrations on the leeward side by 47% when winds were perpendicular posing a higher risk to health, whereas reduced it by 17-42% for parallel winds. The urban air quality and public health can, therefore, be improved by improving the traffic-flow patterns in street canyons as vehicle-induced turbulence has been shown to contribute significantly to dispersion.

  17. pH oscillations in the BrO3--SO3(2-)/HSO3- reaction in a CSTR.

    Science.gov (United States)

    Szantó, Tibor G; Rabai, Gyula

    2005-06-23

    Large-amplitude pH oscillations have been measured during the oxidation of sulfur (IV) species by the bromate ion in aqueous solution in a continuous-flow stirred tank reactor in the absence of any additional oxidizing or reducing reagent. The source of the oscillation in this simple chemical reaction is a two-way oxidation of sulfur (IV) by the bromate ion: (1) the hydrogen-ion-producing self-accelerating oxidation to sulfur (VI) (SO4(2-)), and (2) a hydrogen-ion-consuming oxidation to sulfur (V) (S2O6(2-)). In such a way, both the H+-producing and H+-consuming composite processes required for a pH oscillator take place in parallel in a reaction between two reagents in this system. A simple reaction scheme, consisting of the protonation equilibria of SO3(2-) and HSO3-, the oxidation of HSO3- and H2SO3 by BrO3- to SO4(2-), and the oxidation of H2SO3 to S2O6(2-) has successfully been used to simulate the observed dynamical behavior. Simulation with this simple scheme shows that oscillations can be calculated even if only about 1% of sulfur (IV) is oxidized to S2O6(2-) along with the main product SO4(2-). Agreement between calculated and measured dynamical behavior is found to be quite good. Increasing temperature decreases both the period length of oscillations in a CSTR and the Landolt time measured in a closed reactor. No temperature compensation of the oscillatory frequency is found in this reaction.

  18. WAKE PATTERNS OF FLOW PAST A PAIR OF CIRCULAR CYLINDERS IN SIDE-BY-SIDE ARRANGEMENTS AT LOW REYNOLDS NUMBERS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A flow past two side-by-side identical circular cylinders was numerically investigated with the unstructured spectral element method. From the computational results at various non-dimensional distances between cylinder centers T/D and the Reynolds number Re, a total of nine kinds of wake patterns were observed: four steady wake patterns, including single bluff-body steady pattern, separated double-body steady pattern and transition steady pattern for sub-critical Reynolds numbers and biased steady pattern for super-critical Reynolds numbers, and five unsteady wake patterns, including single bluff-body periodic pattern, biased quasi-steady pattern, quasi-periodic (flip-flopping) pattern, in-phase-synchronized pattern and anti-phase-synchronized pattern. Time evolution of lift and drag coefficients corresponding to each unsteady wake pattern was given.

  19. Ultrasound imaging of flow patterns in liver metastases from colorectal cancer

    DEFF Research Database (Denmark)

    Rafaelsen, Søren Rafael; Solvig, Jan

    2004-01-01

    BACKGROUND: The ability of colour Doppler, power Doppler and echo-enhanced Doppler imaging to detect the blood flow in liver metastases from colorectal cancer was investigated. An evaluation was then made to determine whether the flow pattern could be used as an indication of disease elsewhere....... METHODS: Forty-two patients with hepatic metastases from colorectal cancer were examined, 8 of whom had local recurrence of their colorectal cancer. Seventy-seven liver metastases were evaluated with colour Doppler and power Doppler, and the presence or absence of a Doppler signal in the halo or centre...... detection rate to 98% (P liver...

  20. Experiments and Models of DNA Nano-Catenary Patterns Manipulated by Liquid Flow

    Institute of Scientific and Technical Information of China (English)

    张益; 胡钧; 吴世英; 艾小白; 李民乾

    2002-01-01

    Individual DNA molecules were first stretched by a centrifugal force and adsorbed on a modified mica surface.Then, a liquid flow was guided across the surface along a direction perpendicular to the aligned DNA strands.Some nano-catenary-like patterns of DNA molecules were formed, which were revealed by atomic force microscopy.A physical mechanism called the "s-suspension bridge" model has been presented, by which the features of the catenary-like patterns of DNA molecules can be understood quantitatively quite well.

  1. Internal flow Patterns of the Horizontal Heat Mode Closed-Loop Oscillating Heat Pipe with Check Valves (HHMCLOHP/CV

    Directory of Open Access Journals (Sweden)

    S. Sangiamsuk

    2013-01-01

    Full Text Available This research was to study the internal flow patterns on heat transfer rates of the Horizontal Heat Mode Closed Loop Oscillating Heat Pipe with Check Valves (HHMCLOHP/CV. The HHMCLOHP/CV was made from a Pyrex glass capillary tube with a 2.4 mm inside diameter. There were 10 meandering turns with 2 check valves. Ethanol and a silver nano-ethanol mixture were used as working fluid. Experimental results found that if working fluid varies from ethanol to a silver nano-ethanol mixture and the evaporator temperature increases the main flow patterns were Slug flow + Annular flow. The main regime of each flow pattern can be determined from the flow pattern map.

  2. Groundwater flow pattern and related environmental phenomena in complex geologic setting based on integrated model construction

    Science.gov (United States)

    Tóth, Ádám; Havril, Tímea; Simon, Szilvia; Galsa, Attila; Monteiro Santos, Fernando A.; Müller, Imre; Mádl-Szőnyi, Judit

    2016-08-01

    Groundwater flow, driven, controlled and determined by topography, geology and climate, is responsible for several natural surface manifestations and affected by anthropogenic processes. Therefore, flowing groundwater can be regarded as an environmental agent. Numerical simulation of groundwater flow could reveal the flow pattern and explain the observed features. In complex geologic framework, where the geologic-hydrogeologic knowledge is limited, the groundwater flow model could not be constructed based solely on borehole data, but geophysical information could aid the model building. The integrated model construction was presented via the case study of the Tihany Peninsula, Hungary, with the aims of understanding the background and occurrence of groundwater-related environmental phenomena, such as wetlands, surface water-groundwater interaction, slope instability, and revealing the potential effect of anthropogenic activity and climate change. The hydrogeologic model was prepared on the basis of the compiled archive geophysical database and the results of recently performed geophysical measurements complemented with geologic-hydrogeologic data. Derivation of different electrostratigraphic units, revealing fracturing and detecting tectonic elements was achieved by systematically combined electromagnetic geophysical methods. The deduced information can be used as model input for groundwater flow simulation concerning hydrostratigraphy, geometry and boundary conditions. The results of numerical modelling were interpreted on the basis of gravity-driven regional groundwater flow concept and validated by field mapping of groundwater-related phenomena. The 3D model clarified the hydraulic behaviour of the formations, revealed the subsurface hydraulic connection between groundwater and wetlands and displayed the groundwater discharge pattern, as well. The position of wetlands, their vegetation type, discharge features and induced landslides were explained as

  3. Laminar-turbulent patterning in wall-bounded shear flows: a Galerkin model

    Energy Technology Data Exchange (ETDEWEB)

    Seshasayanan, K [Laboratoire de Physique Statistique, CNRS UMR 8550, École Normale Supérieure, F-75005 Paris (France); Manneville, P, E-mail: paul.manneville@polytechnique.edu [Laboratoire d’Hydrodynamique, CNRS UMR7646, École Polytechnique, F-91128, Palaiseau (France)

    2015-06-15

    On its way to turbulence, plane Couette flow–the flow between counter-translating parallel plates–displays a puzzling steady oblique laminar-turbulent pattern. We approach this problem via Galerkin modelling of the Navier–Stokes equations. The wall-normal dependence of the hydrodynamic field is treated by means of expansions on functional bases fitting the boundary conditions exactly. This yields a set of partial differential equations for spatiotemporal dynamics in the plane of the flow. Truncating this set beyond the lowest nontrivial order is numerically shown to produce the expected pattern, therefore improving over what was obtained at the cruder effective wall-normal resolution. Perspectives opened by this approach are discussed. (paper)

  4. Electrode configurations inside an electrostatic precipitator and their impact on collection efficiency and flow pattern

    Science.gov (United States)

    Ning, Zhiyuan; Cheng, Lu; Shen, Xinjun; Li, Shuran; Yan, Keping

    2016-06-01

    Electrostatic precipitator (ESP) units have wide application in lots industries processes as gas filtration devices. Regarding their high efficiency, further improvement is still required. Wide ESP (plate-to-plate distance greater than 400 mm) is one of a promising way to improve existing ESP due to its ability to reduce equipment investment significantly. However, its large-scale application has been limited because it may potentially lead to collection efficiency reduction. This article focuses on the study of two major effects when several different electrode configurations are applied. The electrohydrodynamic (EHD) flow pattern inside ESP and particle collection efficiency were investigated by using particle image velocimetry (PIV) and electrical low pressure impactor (ELPI) respectively. Results suggested that the collection efficiency of wide ESP is rather complicated and highly related to inner gas flow pattern.

  5. Features of two-phase flow patterns in horizontal rectangular microchannels of height 50 μm

    Directory of Open Access Journals (Sweden)

    Ron’shin Fedor

    2016-01-01

    Full Text Available The horizontal microchannel with the height of 50 micrometres and width of 40 mm of a rectangular cross-section has been used to study two-phase flow. The classical patterns of two-phase flow in the channel (bubble, stratified, churn, jet, and annular have been detected. Experimental information allows us to define the characteristics of the regimes and to determine precisely the boundaries between the patterns of the two-phase flows.

  6. On-line estimation of the dissolved zinc concentration during ZnS precipitation in a CSTR

    NARCIS (Netherlands)

    Grootscholten, T.I.M.; Keesman, K.J.; Lens, P.N.L.

    2007-01-01

    Abstract In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classic

  7. Identification of a Typical CSTR Using Optimal Focused Time Lagged Recurrent Neural Network Model with Gamma Memory Filter

    Directory of Open Access Journals (Sweden)

    S. N. Naikwad

    2009-01-01

    Full Text Available A focused time lagged recurrent neural network (FTLR NN with gamma memory filter is designed to learn the subtle complex dynamics of a typical CSTR process. Continuous stirred tank reactor exhibits complex nonlinear operations where reaction is exothermic. It is noticed from literature review that process control of CSTR using neuro-fuzzy systems was attempted by many, but optimal neural network model for identification of CSTR process is not yet available. As CSTR process includes temporal relationship in the input-output mappings, time lagged recurrent neural network is particularly used for identification purpose. The standard back propagation algorithm with momentum term has been proposed in this model. The various parameters like number of processing elements, number of hidden layers, training and testing percentage, learning rule and transfer function in hidden and output layer are investigated on the basis of performance measures like MSE, NMSE, and correlation coefficient on testing data set. Finally effects of different norms are tested along with variation in gamma memory filter. It is demonstrated that dynamic NN model has a remarkable system identification capability for the problems considered in this paper. Thus FTLR NN with gamma memory filter can be used to learn underlying highly nonlinear dynamics of the system, which is a major contribution of this paper.

  8. Two-phase anaerobic digestion for biogas production from dairy effluent—CSTR and ABR in series

    DEFF Research Database (Denmark)

    Jürgensen, L.; Ehimen, E. A.; Born, J.

    2016-01-01

    retention time of 1.6 d and with changing feed strengths resulting in various organic loading rates between 1.25-4.50 g/(l d). The average COD removal was 82% with a biogas yield of 0.26 l/gCOD. The combination of CSTR and ABR overcame the disadvantages of both reactor types. By further optimization...

  9. On-line estimation of the dissolved zinc concentration during ZnS precipitation in a CSTR

    NARCIS (Netherlands)

    Grootscholten, T.I.M.; Keesman, K.J.; Lens, P.N.L.

    2007-01-01

    Abstract In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classic

  10. The CsoR-like sulfurtransferase repressor (CstR) is a persulfide sensor in Staphylococcus aureus.

    Science.gov (United States)

    Luebke, Justin L; Shen, Jiangchuan; Bruce, Kevin E; Kehl-Fie, Thomas E; Peng, Hui; Skaar, Eric P; Giedroc, David P

    2014-12-01

    How cells regulate the bioavailability of utilizable sulfur while mitigating the effects of hydrogen sulfide toxicity is poorly understood. CstR [Copper-sensing operon repressor (CsoR)-like sulfurtransferase repressor] represses the expression of the cst operon encoding a putative sulfide oxidation system in Staphylococcus aureus. Here, we show that the cst operon is strongly and transiently induced by cellular sulfide stress in an acute phase and specific response and that cst-encoded genes are necessary to mitigate the effects of sulfide toxicity. Growth defects are most pronounced when S. aureus is cultured in chemically defined media with thiosulfate (TS) as a sole sulfur source, but are also apparent when cystine is used or in rich media. Under TS growth conditions, cells fail to grow as a result of either unregulated expression of the cst operon in a ΔcstR strain or transformation with a non-inducible C31A/C60A CstR that blocks cst induction. This suggests that the cst operon contributes to cellular sulfide homeostasis. Tandem high-resolution mass spectrometry reveals derivatization of CstR by both inorganic tetrasulfide and an organic persulfide, glutathione persulfide, to yield a mixture of Cys31-Cys60' interprotomer cross-links, including di-, tri- and tetrasulfide bonds, which allosterically inhibit cst operator DNA binding by CstR.

  11. Film flows and self-organized patterns of 2D-localized structures

    Energy Technology Data Exchange (ETDEWEB)

    Frenkel, A.L. [Univ. of Alabama, Tuscaloosa, AL (United States)

    1996-12-31

    Films flowing down an inclined plane are considered. An unconventional perturbation approach is discussed. It yields the most general evolution equation for film thickness and the least restrictive conditions for its validity. Results of numerical simulations of the dissipative-dispersive evolution equation indicate that novel, more complex type of spatiotemporal patterns can exist for strange attractors of nonequilibrium systems. It is suggested that real-life experiments satisfying the validity conditions of this theory are possible.

  12. Experimental investigation of the interaction of two cylinders in the flow pattern

    Directory of Open Access Journals (Sweden)

    Vitkovičová Rut

    2015-01-01

    Full Text Available This article discusses the behaviour and interaction of two circular cylinders in the flow pattern when one of the cylinders affects wake of the second cylinder. The wake behind the cylinder was investigated experimentally by using a time resolved PIV and CTA method. Velocity fields were obtained for several regimes of Reynolds numbers and several positions of the second cylinder. A frequency of vortex shedding was gained from the acquired images.

  13. Two-dimensional surface river flow patterns measured with paired RiverSondes

    Science.gov (United States)

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.

    2008-01-01

    Two RiverSondes were operated simultaneously in close proximity in order to provide a two-dimensional map of river surface velocity. The initial test was carried out at Threemile Slough in central California. The two radars were installed about 135 m apart on the same bank of the channel. Each radar used a 3-yagi antenna array and determined signal directions using direction finding. The slough is approximately 200 m wide, and each radar processed data out to about 300 m, with a range resolution of 15 m and an angular resolution of 1 degree. Overlapping radial vector data from the two radars were combined to produce total current vectors at a grid spacing of 10 m, with updates every 5 minutes. The river flow in the region, which has a maximum velocity of about 0.8 m/s, is tidally driven with flow reversals every 6 hours, and complex flow patterns were seen during flow reversal. The system performed well with minimal mutual interference. The ability to provide continuous, non-contact two-dimensional river surface flow measurements will be useful in several unique settings, such as studies of flow at river junctions where impacts to juvenile fish migration are significant. Additional field experiments are planned this year on the Sacramento River. ?? 2007 IEEE.

  14. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    Science.gov (United States)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2016-11-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  15. The effect of bowl-in-piston geometry layout on fluid flow pattern

    Directory of Open Access Journals (Sweden)

    Jovanovic Zoran S.

    2011-01-01

    Full Text Available In this paper some results concerning the evolution of 3D fluid flow pattern through all four strokes in combustion chambers with entirely different bowl-in-piston geometry layouts ranging from ”omega” to “simple cylinder” were presented. All combustion chambers i.e. those with „omega“ bowls, with different profiles, and those with „cylinder“ bowls, with different squish area ranging from 44% to 62%, were with flat head, vertical valves and identical elevation of intake and exhaust ports. A bunch of results emerged by dint of multidimensional modeling of nonreactive fluid flow in arbitrary geometry with moving objects and boundaries. The fluid flow pattern during induction and compression in all cases was extremely complicated and entirely three-dimensional. It should be noted that significant differences due to geometry of the bowl were encountered only in the vicinity of TDC. Namely, in the case of “omega” bowl all three types of organized macro flows were observed while in the case of “cylinder” bowl no circumferential velocity was registered at all. On the contrary, in the case of “cylinder” bowl some interesting results concerning reverse tumble and its center of rotation shifting from exhaust valve zone to intake valve zone during induction stroke and vice-verse from intake valve zone to exhaust valve zone during compression were observed while in the case of “omega” bowl no such a displacement was legible. During expansion the fluid flow pattern is fully controlled by piston motion and during exhaust it is mainly one-dimensional, except in the close proximity of exhaust valve. For that reason it is not affected by the geometry of the bowl.

  16. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    Science.gov (United States)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2017-02-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  17. Two-phase flow pattern recognition in a varying section based on void fraction and pressure measurements

    Science.gov (United States)

    de Kerret, F.; Benito, I.; Béguin, C.; Pelletier, D.; Etienne, S.

    2016-11-01

    In a hydroelectric turbine, the air injected during operation has an impact on the yield of the machine leading to important losses of energy. To understand those losses and be able to reduce them, a first step is to understand the pattern of the two-phase flows and describe their characteristics in the turbine. Those two-phase flows can be bubbly, intermittent, or annular, with different types of intermittent flow possible. Two-phase flow patterns are well defined in classical geometries such as cylinders with reliable descriptions available [5]. But, there is a critical lack of knowledge for flow patterns in other geometries. In our present work we take interest into a geometry that is a pipe with periodical changes of the section and realize a flow pattern map. To realize this map, we measure the pressure variations and void fraction fluctuations while changing the flow rates of water and air in our test section. We then use our physical understanding of the phenomena to analyze data and identify different flow patterns, characterize them, and build a new flow pattern map.

  18. Sediment Deposition Pattern and Flow Conditions in the Three Gorges Reservoir: A Physical Model Study

    Institute of Scientific and Technical Information of China (English)

    王兴奎; 邵学军; 李丹勋

    2003-01-01

    Sedimentation in the Three Gorges Reservoir will greatly affect future project functions, such as power generation and navigation, after 50 years of operation. This paper presents results of a physical model study, which indicate that the capacity of both the discharge tunnel and the power plant outlet could be impaired by sediment deposition in front of the dam after 50 years, affecting both the hydropower head and navigation. A flow training scheme based on the third-stage cofferdam for the dam construction is proposed to regulate the flow pattern and control deposition in the near-dam region of the reservoir. This flow training scenario can effectively reduce deposition in the physical model.

  19. CSTR和ACR丁酸型发酵制氢系统的运行特性比较%Operation characteristic comparison of CSTR and ACR systems for hydrogen production by butyric acid type fermentation

    Institute of Scientific and Technical Information of China (English)

    李建政; 于泽; 昌盛; 苏晓煜

    2012-01-01

    In order to structure a better continuous flow bioreactor mode for fermentative hydrogen production, a continuous stirred-tank reactor (CSTR) and an anaerobic contact digester (ACR) were evaluated with diluted molasses as raw material, and their operation characteristics during starting and running were analyzed and compared. Inoculated with aerobic pretreated sewage sludge, both the reactors started up at (35 ±1l)°C with an initial volatile suspended sludge (MLVSS) of 4. 8 g · L-1, a hydraulic retention time (HRT) of 12 h and an influent chemical oxygen demand (COD) of 5000 mg · L-1. The pH was controlled at 5. 5-6. 0 in both fermentation systems during the whole operation period. The results showed that the CSTR could reach steady butyric acid type fermentation in 15 d, much faster than in 25 d for ACR. During the steady state, the butyrate was dominated among the soluble metabolites and counted for 53% and 50% of the total liquid products in CSTR and ACR system, respectively. The hydrogen-producing efficiency was higher for ACR than for CSTR, indicating its better ability to maintain biomass. The substrate acidification ratio, the hydrogen production rate and specific hydrogen production rate of the sludge were 44% , 9 L · d-1 and 0. 15 L · (g MLVSS · d) -1, respectively, for the steady ACR system, and 1. 62, 2. 05 and 1. 15 times of corresponding values of CSTR system.%为寻求更好的连续流发酵生物制氧反应器模式,以稀释糖蜜为底物,控制反应系统为丁酸型发酵,比较研究了搅拌槽式反应器(CSTR)和厌氧接触式反应器(ACR)的启动运行特性.结果表明,以经曝气培养的下水道污泥为接种物,在接种量4.8gMLVSS·L-1、进水COD 5000 mg·L-1、HRT 12 h、温度(35±1)℃和pH 5.5~6.0等相同条件下,CSTR系统可以更快地达到稳定的丁酸型发酵状态,而ACR系统因其有效的生物持有能力而在产氢性能方面更具优势.在稳定运行状态下,ACR系统的底物酸化率

  20. How the propagation of heat-flux modulations triggers E × B flow pattern formation.

    Science.gov (United States)

    Kosuga, Y; Diamond, P H; Gürcan, O D

    2013-03-08

    We propose a novel mechanism to describe E×B flow pattern formation based upon the dynamics of propagation of heat-flux modulations. The E × B flows of interest are staircases, which are quasiregular patterns of strong, localized shear layers and profile corrugations interspersed between regions of avalanching. An analogy of staircase formation to jam formation in traffic flow is used to develop an extended model of heat avalanche dynamics. The extension includes a flux response time, during which the instantaneous heat flux relaxes to the mean heat flux, determined by symmetry constraints. The response time introduced here is the counterpart of the drivers' response time in traffic, during which drivers adjust their speed to match the background traffic flow. The finite response time causes the growth of mesoscale temperature perturbations, which evolve to form profile corrugations. The length scale associated with the maximum growth rate scales as Δ(2) ~ (v(thi)/λT(i))ρ(i)sqrt[χ(neo)τ], where λT(i) is a typical heat pulse speed, χ(neo) is the neoclassical thermal diffusivity, and τ is the response time of the heat flux. The connection between the scale length Δ(2) and the staircase interstep scale is discussed.

  1. Analysis of fluid flow and wall shear stress patterns inside partially filled agitated culture well plates.

    Science.gov (United States)

    Salek, M Mehdi; Sattari, Pooria; Martinuzzi, Robert J

    2012-03-01

    The appearance of highly resistant bacterial biofilms in both community and hospitals environments is a major challenge in modern clinical medicine. The biofilm structural morphology, believed to be an important factor affecting the behavioral properties of these "super bugs", is strongly influenced by the local hydrodynamics over the microcolonies. Despite the common use of agitated well plates in the biology community, they have been used rather blindly without knowing the flow characteristics and influence of the rotational speed and fluid volume in these containers. The main purpose of this study is to characterize the flow in these high-throughput devices to link local hydrodynamics to observed behavior in cell cultures. In this work, the flow and wall shear stress distribution in six-well culture plates under planar orbital translation is simulated using Computational Fluid Dynamics (CFD). Free surface, flow pattern and wall shear stress for two shaker speeds (100 and 200 rpm) and two volumes of fluid (2 and 4 mL) were investigated. Measurements with a non-intrusive optical shear stress sensor and High Frame-rate Particle Imaging Velocimetry (HFPIV) are used to validate CFD predictions. An analytical model to predict the free surface shape is proposed. Results show a complex three-dimensional flow pattern, varying in both time and space. The distribution of wall shear stress in these culture plates has been related to the topology of flow. This understanding helps explain observed endothelial cell orientation and bacterial biofilm distributions observed in culture dishes. The results suggest that the mean surface stress field is insufficient to capture the underlying dynamics mitigating biological processes.

  2. Effective Medium Theory for Drag Reducing Micro-patterned Surfaces in Turbulent Flows

    CERN Document Server

    Battiato, Ilenia

    2013-01-01

    Inspired by the lotus effect, many studies in the last decade have focused on micro- and nano-patterned surfaces. They revealed that patterns at the micro-scale combined with high contact angles can significantly reduce skin drag. However, the mechanisms and parameters that control drag reduction, e.g. Reynolds number and pattern geometry, are still unclear. We propose an effective medium representation of the micro-features, that treats the latter as a porous medium, and provides a framework to model flow over patterned surfaces in both Cassie and Wenzel states. Our key result is a closed-form expression for the skin friction coefficient in terms of frictional Reynolds (or K\\'arm\\'an) number in turbulent regime, the viscosity ratio between the fluid in and above the features, and their geometrical properties. We apply the proposed model to turbulent flows over superhydrophobic ridged surfaces. The model predictions agree with laboratory experiments for Reynolds numbers ranging from 3000 to 10000.

  3. Anaerobic co-digestion of waste activated sludge and greasy sludge from flotation process: Batch versus CSTR experiments to investigate optimal design

    OpenAIRE

    Girault, R.; Bridoux, G.; Nauleau, F.; Poullain, C.; Buffet, J.; Peu, P.; Sadowski, A.G.; Béline, F.

    2012-01-01

    In this study, the maximum ratio of greasy sluvdge to incorporate with waste activated sludge was investigated in batch and CSTR experiments. In batch experiments, inhibition occurred with a greasy sludge ratio of more than 20-30% of the feed COD. In CSTR experiments, the optimal greasy sludge ratio was 60% of the feed COD and inhibition occurred above a ratio of 80%. Hence, batch experiments can predict the CSTR yield when the degradation phenomenon are additive but cannot be used to determi...

  4. Stirring effects and bistability in the iodate-arsenous acid reaction: Premixed vs segregated flows

    Science.gov (United States)

    Hannon, L.; Horsthemke, W.

    1987-01-01

    Using a coalescence-dispersion model of the continuous flow-stirred tank reactor (CSTR), we study the effect of premixed vs nonpremixed reactant flows on chemical bistability. The region of bistability is smaller for segregated feed streams than for a fully premixed feed stream. The transition from flow branch to thermodynamic branch is particularly sensitive to the feed stream configuration.

  5. Linking fault pattern with groundwater flow in crystalline rocks at the Grimsel Test Site (Switzerland)

    Science.gov (United States)

    Schneeberger, Raphael; Berger, Alfons; Mäder, Urs K.; Niklaus Waber, H.; Kober, Florian; Herwegh, Marco

    2017-04-01

    Water flow across crystalline bedrock is of major interest for deep-seated geothermal energy projects as well as for underground disposal of radioactive waste. In crystalline rocks enhanced fluid flow is related to zones of increased permeability, i.e. to fractures that are associated to fault zones. The flow regime around the Grimsel Test Site (GTS, Central Aar massif) was assessed by establishing a 3D fault zone pattern on a local scale in the GTS underground facility (deca-meter scale) and on a regional scale at the surface (km-scale). The study reveals the existence of a dense fault zone network consisting of several km long and few tens of cm to meter wide, sub-vertically oriented major faults that are connected by tens to hundreds of meters long minor bridging faults. This geometrical information was used as input for the generation of a 3D fault zone network model. The faults originate from ductile shear zones that were reactivated as brittle faults under retrograde conditions during exhumation. Embrittlement and associated dilatancy along the faults provide the pathways for today's groundwater flow. Detection of the actual 3D flow paths is, however, challenging since flow seem to be not planar but rather tube-like. Two strategies are applied to constrain the 3D geometry of the flow tubes: (i) Characterization of the groundwater infiltrating into the GTS (location, yield, hydraulic head, and chemical composition) and (ii) stress modelling on the base of the 3D structural model to unravel potential domains of enhanced fluid flow such as fault plane intersections and domains of dilatancy. At the Grimsel Test Site, hydraulic and structural data demonstrate that the groundwater flow is head-driven from the surface towards the GTS located some 450 m below the surface. The residence time of the groundwater in this surface-near section is >60 years as evidenced by absence of detectable tritium. However, hydraulic heads obtained from interval pressure measurements

  6. Flow patterns and heat convection in a rectangular water bolus for use in superficial hyperthermia.

    Science.gov (United States)

    Birkelund, Yngve; Jacobsen, Svein; Arunachalam, Kavitha; Maccarini, Paolo; Stauffer, Paul R

    2009-07-07

    This paper investigates both numerically and experimentally the spatio-temporal effects of water flow in a custom-made water bolus used for superficial hyperthermia generated by a 915-MHz, 4 x 3 microwave applicator array. Similar hyperthermia models referenced in the literature use a constant water temperature and uniform heat flux to describe conduction and convection energy exchange within the heating apparatus available to cool the tissue surface. The results presented in this paper show that the spatially varying flow pattern and rate are vital factors for the overall heat control applicability of the 5 mm thick bolus under study. Regions with low flow rates and low heat convection clearly put restrictions on the maximum microwave energy possible within the limits of skin temperature rise under the bolus. Our analysis is illustrated by experimental flow front studies using a contrast liquid set-up monitored by high definition video and complemented by numerical analysis of liquid flow and heat exchange within the rectangular water bolus loaded by malignant tissue. Important factors for the improvement of future bolus designs are also discussed in terms of diameter and configuration of the water input and output tubing network.

  7. Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

    Directory of Open Access Journals (Sweden)

    K. Schraml

    2015-02-01

    Full Text Available Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. For this, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS-DF (Rapid Mass Movement System – Debris Flow and DAN3D (Dynamic Analysis of Landslides in Three Dimensions, to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation model with a 1 m resolution and similar initial conditions. Our results show that both simulation tools are capable of matching observed deposition patterns. The best fit parameter set of μ [–] and ξ [m s−2] range between 0.07–0.11 and 200–300 m s−2, respectively, for RAMMS-DF, and 0.07–0.08 and 300–400 m s−2, respectively, for DAN3D. Sensitivity analyses show a higher sensitivity of model parameters for the DAN3D model than for the RAMMS-DF model. This study shall contribute to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

  8. A landscape lake flow pattern design approach based on automated CFD simulation and parallel multiple objective optimization.

    Science.gov (United States)

    Guo, Hao; Tian, Yimei; Shen, Hailiang; Wang, Yi; Kang, Mengxin

    A design approach for determining the optimal flow pattern in a landscape lake is proposed based on FLUENT simulation, multiple objective optimization, and parallel computing. This paper formulates the design into a multi-objective optimization problem, with lake circulation effects and operation cost as two objectives, and solves the optimization problem with non-dominated sorting genetic algorithm II. The lake flow pattern is modelled in FLUENT. The parallelization aims at multiple FLUENT instance runs, which is different from the FLUENT internal parallel solver. This approach: (1) proposes lake flow pattern metrics, i.e. weighted average water flow velocity, water volume percentage of low flow velocity, and variance of flow velocity, (2) defines user defined functions for boundary setting, objective and constraints calculation, and (3) parallels the execution of multiple FLUENT instances runs to significantly reduce the optimization wall-clock time. The proposed approach is demonstrated through a case study for Meijiang Lake in Tianjin, China.

  9. A probabilistic approach to quantifying spatial patterns of flow regimes and network-scale connectivity

    Science.gov (United States)

    Garbin, Silvia; Alessi Celegon, Elisa; Fanton, Pietro; Botter, Gianluca

    2017-04-01

    The temporal variability of river flow regime is a key feature structuring and controlling fluvial ecological communities and ecosystem processes. In particular, streamflow variability induced by climate/landscape heterogeneities or other anthropogenic factors significantly affects the connectivity between streams with notable implication for river fragmentation. Hydrologic connectivity is a fundamental property that guarantees species persistence and ecosystem integrity in riverine systems. In riverine landscapes, most ecological transitions are flow-dependent and the structure of flow regimes may affect ecological functions of endemic biota (i.e., fish spawning or grazing of invertebrate species). Therefore, minimum flow thresholds must be guaranteed to support specific ecosystem services, like fish migration, aquatic biodiversity and habitat suitability. In this contribution, we present a probabilistic approach aiming at a spatially-explicit, quantitative assessment of hydrologic connectivity at the network-scale as derived from river flow variability. Dynamics of daily streamflows are estimated based on catchment-scale climatic and morphological features, integrating a stochastic, physically based approach that accounts for the stochasticity of rainfall with a water balance model and a geomorphic recession flow model. The non-exceedance probability of ecologically meaningful flow thresholds is used to evaluate the fragmentation of individual stream reaches, and the ensuing network-scale connectivity metrics. A multi-dimensional Poisson Process for the stochastic generation of rainfall is used to evaluate the impact of climate signature on reach-scale and catchment-scale connectivity. The analysis shows that streamflow patterns and network-scale connectivity are influenced by the topology of the river network and the spatial variability of climatic properties (rainfall, evapotranspiration). The framework offers a robust basis for the prediction of the impact of

  10. Neural Network Control of CSTR for Reversible Reaction Using Reverence Model Approach

    Directory of Open Access Journals (Sweden)

    Duncan ALOKO

    2007-01-01

    Full Text Available In this work, non-linear control of CSTR for reversible reaction is carried out using Neural Network as design tool. The Model Reverence approach in used to design ANN controller. The idea is to have a control system that will be able to achieve improvement in the level of conversion and to be able to track set point change and reject load disturbance. We use PID control scheme as benchmark to study the performance of the controller. The comparison shows that ANN controller out perform PID in the extreme range of non-linearity.This paper represents a preliminary effort to design a simplified neutral network control scheme for a class of non-linear process. Future works will involve further investigation of the effectiveness of thin approach for the real industrial chemical process

  11. CONTROL OF CONCENTRATION IN CSTR USING DMC AND CONVENTIONAL PID BASED ON RELAY FEEDBACK METHOD

    Directory of Open Access Journals (Sweden)

    S. SRINIVASULU RAJU

    2013-04-01

    Full Text Available This paper presents the design of a Dynamic Matrix Controller (DMC is analyzed for concentration control of Continuous Stirred Tank Reactors (CSTRs which have strong nonlinearities. Various control approaches have been applied on CSTR to control its parameters. All the industrial process applications require solutions of a specific chemical strength of the chemicals or fluids considered for analysis. Such specific concentrations are achieved by mixing a full strength solution with water in the desired proportions. For this, we use twocontrollers DMC and PID and analyzed. The basic PID controllers have difficulty in dealing with complex nonlinear processes. Simulation studies give satisfactory results. In this paper the control the concentration of one chemical with the help of other has been analyzed. Model design and simulation are done in MATLAB/SIMULINK, using programming. The concentration control is found better controlled with the addition of DMC instead of PID controller solely.

  12. Sensitivity analysis of a biofilm model describing mixed growth of nitrite oxidisers in a CSTR.

    Science.gov (United States)

    Kornaros, M; Dokianakis, S N; Lyberatos, G

    2006-01-01

    A simple kinetic model has been developed for describing nitrite oxidation by autotrophic aerobic nitrifiers in a CSTR reactor, in which mixed (suspended and attached) growth conditions are prevailing. In this work, a critical dimensionless parameter is identified containing both biofilm characteristics and microbial kinetic parameters, as well as the specific (per volume) surface of the reactor configuration used. Evaluation of this dimensionless parameter can easily provide information on whether or not wall attachment is critical, and should be taken into account either in kinetic studies or in reactor design, when specific pollutants are to be removed from the waste influent stream. The effect of bulk dissolved oxygen (DO) concentration on the validity of this model is addressed and minimum non-limiting DO concentrations are proposed depending on the reactor configuration.

  13. Flow patterns of GaInSn liquid on inclined stainless steel plate under a range of magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Juan-Cheng, E-mail: yangjc@xjtu.edu.cn [State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an, Shanxi 710049 (China); Qi, Tian-Yu [School of Engineering Sciences, University of Chinese Academy and Sciences, Beijing 100049 (China); Ni, Ming-Jiu, E-mail: mjni@ucas.ac.cn [School of Engineering Sciences, University of Chinese Academy and Sciences, Beijing 100049 (China); Wang, Zeng-Hui [School of Engineering Sciences, University of Chinese Academy and Sciences, Beijing 100049 (China)

    2016-11-01

    Highlights: • The liquid GaInSn metal flow loop was built to study some fusion related liquid metal MHD phenomenon. • The flow patterns of GaInSn free surface flow with the change of Re number and Ha number were got by lot of experiments. • Some detailed descriptions of these flow patterns were also made, and a solid conclusion which agreed with some previous studies was got. - Abstract: In the present paper, some preliminary experimental studies have been conducted to show the flow pattern of liquid metal flow using visualization method. For the convenience of experiments in lab, Ga{sup 67}In{sup 20.5}Sn{sup 12.5} in liquid state at room temperature is used. A test section made by stainless steel is inserted in a traverse magnetic field with strength (B{sub 0}) varies from 0 to 1.28 T. The inclined angle of stainless steel plate in test section is about 9°. Visualization results obtained by high-speed camera (Phantom M/LC 310) shown that GaInSn liquid flow on inclined stainless steel plate behaved unstable liquid column flow pattern in the low flow rate, while behaved large area spreading flow pattern with small waves on the free surface in the large flow rate. However, in the magnetic field, under the action of electromagnetic force, the flow patterns of GaInSn liquid have some significant changes on the spreading width and surface structure of free surface. Some detailed analyses on these changes have been also showed in the present paper. Plans for future work are also presented.

  14. Comparison of cerebral blood flow pattern by transcranial Doppler in patients with diffuse and focal causes of brain death

    Directory of Open Access Journals (Sweden)

    Alireza Vakilian

    2012-01-01

    Full Text Available Background: This study aims to assess the cerebral vessels flow in brain death patients with different causes, including focal and diffuse lesions and comparison of flows according to the underlying causes. Materials and Methods: Two groups of 15 brain-dead patients one with focal and the other with diffuse brain lesions were compared according to their cerebral blood flow pattern 48 h passed brain death certification. Results: Bilateral absence of flow in middle cerebral artery (MCA was found in 54.5% of brain-dead patients with diffuse lesion and 50.33% of those with focal lesions. Systolic spike pattern in MCA flow was found in 46.2% of patients with focal lesion and 16.65% of patients with diffuse lesion. Diastole-systole separation pattern in MCA was seen in 16.65% of patients with the diffuse lesions. This pattern in MCA was not seen in patients with the focal lesion group. In carotid arteries, we did not find the absence of flow in any cases. Thirty percent of all patients in both groups had a normal flow pattern (36.6% of patients with focal lesions and 23.3% of patients with diffuse lesion. Patients with focal lesion had 33.3% systolic spike pattern flow and had 23.35% diastole-systole separation flow pattern. In intra-cranial vessels, systolic spike pattern was more common among patients with focal lesions than patients with diffuse lesion, however, this difference was not statistically significant (46.2% of patients with focal lesion and 16.65% of patients with diffuse lesion (P value = 0.244-0.09. Diastole-systole separation flow was more common in patients with diffuse lesions than those with the focal lesions although this could not reach the significant level as the previous pattern (20% of patients with diffuse lesion versus no case in patients with focal lesion (P value = 0.181. Conclusion: Absence of flow was the most common brain flow pattern in the focal and diffuse group lesions. There was no difference in flow pattern

  15. A clinical study on velocity patterns of pulmonary venous flow in canine heartworm disease.

    Science.gov (United States)

    Shibata, T; Wakao, Y; Takahashi, M

    2000-02-01

    In this study, we evaluated methods of determining the velocity patterns of pulmonary venous flow (PVF) in dogs and then investigated the relationship of the patterns to cardiac functions in heartworm disease (HD) by transthoracic echocardiography (TTE). The results revealed that there was a good correlation between PVF patterns determined by transesophageal echocardiography (TEE) and TTE in animals lying on their left sides. The measurement of S and D wave velocities (PVS and PVD) by TTE was shown to allow clinical determination of the velocity patterns of PVF in dogs. The HD groups showed significant increases in PVS and PVD, and S and D wave time-velocity integrals (S-TVI and D-TVI) of the right cranial lobe PVF, when compared with the normal group, as determined by TTE (P<0.05). In contrast, the HD groups produced significant decreases in PVD and D-TVI of the right caudal lobe PVF compared with the normal group (P<0.05), and a significant increase in the ratio of S-TVI to (S-TVI + D-TVI) (P<0.05). It is, therefore, suggested that measurement of the velocity patterns of the right cranial and caudal lobe PVF could be one method of assessing the stages of obstructive lesions in the pulmonary artery.

  16. Buoyancy effect on the flow pattern and the thermal performance of an array of circular cylinders

    CERN Document Server

    Fornarelli, Francesco; Oresta, Paolo

    2016-01-01

    In this paper we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are iso-thermal and they are aligned with the Earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between -1 and 1. Two values of center to center spacing (s=3.6d - 4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri=-1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard d...

  17. A D-Shaped Bileaflet Bioprosthesis which Replicates Physiological Left Ventricular Flow Patterns.

    Directory of Open Access Journals (Sweden)

    Sean Guo-Dong Tan

    Full Text Available Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation.

  18. Patterning of ultrathin polymethylmethacrylate films by in-situ photodirecting of the Marangoni flow

    Science.gov (United States)

    Elashnikov, Roman; Fitl, Premysl; Svorcik, Vaclav; Lyutakov, Oleksiy

    2017-02-01

    Laser heating and Marangoni flow result in the formation of surface structures with different geometries and shape on thin polymer films. By laser beam irradiation combined with a sample movement the solid polymethylmethacrylate (PMMA) films are heated and undergo phase transition which leads to a material flow. Since the laser beam has a non-linear distribution of energy, the PMMA film is heated inhomogeneously and a surface tension gradient in a lateral direction is introduced. During this procedure additional phenomena such as "reversible" or cyclic polymer flow also take place. The careful choice of experimental conditions enables the preparation of patterns with sophisticated geometries and with hierarchical pattern organization. Depending on initial PMMA film thickness and speed of the sample movement line arrays are created, which can subsequently be transformed into the crimped lines or system of circular holes. In addition, the introduction of a constant acceleration in the sample movement or a laser beam distortion enables the preparation of regularly crimped lines, ordered hexagonal holes or overlapped plates.

  19. Two-dimensional intraventricular flow pattern visualization using the image-based computational fluid dynamics.

    Science.gov (United States)

    Doost, Siamak N; Zhong, Liang; Su, Boyang; Morsi, Yosry S

    2016-10-31

    The image-based computational fluid dynamics (IB-CFD) technique, as the combination of medical images and the CFD method, is utilized in this research to analyze the left ventricle (LV) hemodynamics. The research primarily aims to propose a semi-automated technique utilizing some freely available and commercial software packages in order to simulate the LV hemodynamics using the IB-CFD technique. In this research, moreover, two different physiological time-resolved 2D models of a patient-specific LV with two different types of aortic and mitral valves, including the orifice-type valves and integrated with rigid leaflets, are adopted to visualize the process of developing intraventricular vortex formation and propagation. The blood flow pattern over the whole cardiac cycle of two models is also compared to investigate the effect of utilizing different valve types in the process of the intraventricular vortex formation. Numerical findings indicate that the model with integrated valves can predict more complex intraventricular flow that can match better the physiological flow pattern in comparison to the orifice-type model.

  20. On the growth of laminar-turbulent patterns in plane Couette flow

    CERN Document Server

    Manneville, Paul

    2012-01-01

    The growth of laminar-turbulent band patterns in plane Couette flow is studied in the vicinity of the global stability threshold R_g below which laminar flow ultimately prevails. Appropriately tailored direct numerical simulations are performed to manage systems extended enough to accommodate several bands. The initial state or germ is an oblique turbulent patch of limited extent. The growth is seen to result from several competing processes: (i) nucleation of turbulent patches close to or at the extremities of already formed band segments, with the same obliquity as the germ or the opposite one, and (ii) turbulence collapse similar to gap formation for band decay. Growth into a labyrinthine pattern is observed as soon as spanwise expansion is effective. An ideally aligned pattern is usually obtained at the end of a long and gradual regularisation stage when R is large enough. Stable isolated bands can be observed slightly above R_g. When growth rates are not large enough, the germ decays at the end of a long...

  1. Fluid flow pattern and water residence time in waste stabilisation ponds.

    Science.gov (United States)

    Badrot-Nico, F; Guinot, V; Brissaud, F

    2009-01-01

    As treatment processes are kinetic-dependent, a consistent description of water residence times is essential to the prediction of waste stabilization ponds performance. A physically-based 3D transient CFD model simulating the water velocity, temperature and concentration fields as a function of all influent meteorological factors--wind speed and direction, solar radiation, air temperature and relative humidity--was used to identify the relationships between the meteorological conditions and the hydrodynamic patterns and water residence times distributions in a polishing pond. The required meteorological data were recorded on site and water temperatures recorded at 10 sampling sites for 141 days. Stratification events appear on very calm days for wind speeds lower than 3 m s(-1) and on sunny days for wind speeds lower than 5 m s(-1). De-stratification is related to two mixing processes: nightly convection cells and global mixing patterns. Numerical tracer experiments show that the results of the flow patterns can be evaluated using the dispersed flow regime approximation and, for wind speeds exceeding 6 m s(-1), the completely stirred tank reactor assumption.

  2. Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

    Science.gov (United States)

    Husain, Taha Murtuza

    Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

  3. Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

    Directory of Open Access Journals (Sweden)

    Minghui Li

    2016-05-01

    Full Text Available The permeability of coal is a critical parameter in estimating the performance of coal reservoirs. Darcy’s law describes the flow pattern that the permeability has a linear relationship with the flow velocity. However, the stress induced deformation and damage can significantly influence the gas flow pattern and permeability of coal. Coals from Songzao coalfield in Chongqing, southwest China were collected for the study. The gas flow velocities under different injection gas pressures and effective stresses in the intact coal and damaged coal were tested using helium, incorporating the role of gas flow pattern on the permeability of coal. The relationships between the flow velocity and square of gas pressure gradient were discussed, which can help us to investigate the transformation conditions of gas linear flow and gas nonlinear flow in the coal. The results showed that the gas flow in the intact coal existed pseudo-initial flow rate under low effective stress. The low-velocity non-Darcy gas flow gradually occurred and the start-up pressure gradient increased in the coal as the effective stress increased. The gas flow rate in the damaged coal increased nonlinearly as the square of pressure gradient increased under low effective stress. The instability of gas flow caused by high ratio of injection gas pressure over effective stress in the damaged coal contributed to the increase of the gas flow rate. As the effective stress increased, the increase of gas flow rate in coal turned to be linear. The mechanisms of the phenomena were explored according to the experimental results. The permeability of coal was corrected based on the relationships between the flow velocity and square of gas pressure gradient, which showed advantages in accurately estimating the performance of coal reservoirs.

  4. 二次型CSTR模型和SG模型的恒稳定解的degree%Degree of Steady-state Solutions of Quadratic CSTR Model and SG Model

    Institute of Scientific and Technical Information of China (English)

    廉进国; 孙炯

    2006-01-01

    Two systems of nonlinear ordinary differential equations are studied,which are quadratic CSTR model and SG model.Strictly positive invariant regions are found for these models.It is shown that for each model,there exists only one steady-state solution in invariant region and its degree equals 1.These establish a foundation for studying the patterns of the extended quadratic CSTR model and SG model.%研究了两个非线性常微分方程系统二次型CSTR模型和SG模型.证明了这两个模型分别存在一个严格的正不变区域且它们在各自的正不变区域内只有一个恒稳定解,这个恒稳定解的Degree是1.这为研究推广的二次型CSTR模型和SG模型解的存在性奠定了基础.

  5. Patterns of fetal lamb regional cerebral blood flow during and after prolonged hypoxia.

    Science.gov (United States)

    Ashwal, S; Majcher, J S; Vain, N; Longo, L D

    1980-10-01

    In an effort to determine to what extent cerebral blood flow (CBF) varies in different parts of the brain during prolonged fetal hypoxia, we measured flow to 34 regions in 12 chronically catheterized fetal lambs 130 to 140 days gestation. Control values of PO2, PCO2 pH, heart rate, and blood pressure were obtained, and CBF was measured by use of radioactive labeled microspheres during a control period, during (15-, 30-, and 90-min) reduction of maternal inspired O2 concentration (fetal arterial PO2 was maintained at 12 to 15 torr), and 60 min after returning the ewe to room air. control blood flow to cortical, subcortical, and brainstem structures equaled 134, 186, and 254 ml x min-1 x 100 g-1, respectively. During hypoxia, CBF increased 92%, and 60 min after fetal oxygenation was restored, it remained 50% above control values. We noted a similar response in regional CBF to the cortex, subcortex, and brainstem during and after hypoxia. Blood flow to smaller areas within the three major regions were quite homogenous and had a similar pattern of response to hypoxia. We conclude that: (1) significant fetal regional CBF differences occurred in utero with brainstem and subcortical flows being substantially greater than flows to other regions of the brain; (2) during prolonged intrauterine hypoxia, total regional CBF increased 92%; (3) 1 hr after fetal oxygenation was restored, CBF still remained 50% above control values; and finally, (4) there was no significant preferential shunting of regional CBF during prolonged hypoxia in utero.

  6. The prescribed output pattern regulates the modular structure of flow networks

    Science.gov (United States)

    Emanuel Beber, Moritz; Armbruster, Dieter; Hütt, Marc-Thorsten

    2013-11-01

    Modules are common functional and structural properties of many social, technical and biological networks. Especially for biological systems it is important to understand how modularity is related to function and how modularity evolves. It is known that time-varying or spatially organized goals can lead to modularity in a simulated evolution of signaling networks. Here, we study a minimal model of material flow in networks. We discuss the relation between the shared use of nodes, i.e., the cooperativity of modules, and the orthogonality of a prescribed output pattern. We study the persistence of cooperativity through an evolution of robustness against local damages. We expect the results to be valid for a large class of flow-based biological and technical networks. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjb/e2013-40672-3

  7. Control Theoretic Modeling and Generated Flow Patterns of a Fish-Tail Robot

    Science.gov (United States)

    Massey, Brian; Morgansen, Kristi; Dabiri, Dana

    2003-11-01

    Many real-world engineering problems involve understanding and manipulating fluid flows. One of the challenges to further progress in the area of active flow control is the lack of appropriate models that are amenable to control-theoretic studies and algorithm design and also incorporate reasonably realistic fluid dynamic effects. We focus here on modeling and model-verification of bio-inspired actuators (fish-fin type structures) used to control fluid dynamic artifacts that will affect speed, agility, and stealth of Underwater Autonomous Vehicles (UAVs). Vehicles using fish-tail type systems are more maneuverable, can turn in much shorter and more constrained spaces, have lower drag, are quieter and potentially more efficient than those using propellers. We will present control-theoretic models for a simple prototype coupled fluid and mechanical actuator where fluid effects are crudely modeled by assuming only lift, drag, and added mass, while neglecting boundary effects. These models will be tested with different control input parameters on an experimental fish-tail robot with the resulting flow captured with DPIV. Relations between the model, the control function choices, the obtained thrust and drag, and the corresponding flow patterns will be presented and discussed.

  8. ANN BASED CONTROL PATTERNS ESTIMATOR FOR UPFC USED IN POWER FLOW PROBLEM

    Directory of Open Access Journals (Sweden)

    K.Krishnaveni

    2007-09-01

    Full Text Available The continuous growth in the demand for electric power necessitates the flexibility of operation in power system. Of different power electronics-based Flexible AC Transmission System (FACTS devices, which enhance the power transmission capabilities, Unified Power Flow Controller (UPFC provides an emerging and promising solution for the power flow problems in the system, as it simultaneously and/or selectively controls the transmission parameters. In this context, the paper proposes the power flow control in a simple system by injecting the series compensating voltage, which is an important function of UPFC. For this purpose, ANN controller based UPFC is used. Control patterns are generated for obtaining the adjustable series voltage from the second converter that, in turn, controls the power flow in the system. With the proposed model, by varying control coefficient the series injected voltage can be adjusted. MATLAB Simulation is used to test the proposed model. The control horizon is identified and presented for various values of existing active and reactive powers.

  9. How the Propagation of Heat-Flux Modulations Triggers E × B Flow Pattern Formation

    Science.gov (United States)

    Kosuga, Yusuke

    2013-10-01

    Recently, a new class of E × B flow pattern, called an `` E × B staircase,'' was observed in a simulation study using the full- f flux driven GYSELA code. Here, E × B staircases are quasi-regular steady patterns of localized shear layers and temperature profile corrugations. The shear layers are interspaced between regions of turbulent avalanching of the size of several correlation length (~ 10Δc). In this work, a theory to describe the formation of such E × B staircases from a bath of stochastic avalanches is presented, based on analogy of staircase formation to jam formation in traffic flow. Namely, staircase formation is viewed as a heat flux ``jam'' that causes profile corrugation, which is analogous to a traffic jam that causes corrugations in the local car density in a traffic flow. To model such an effect in plasmas, a finite response time τ is introduced, during which instantaneous heat flux relaxes to the mean heat flux, determined by symmetry constraints. The response time introduced here is an analogue of drivers' response time in traffic flow dynamics. It is shown that the extended model describes a heat flux ``jam'' and profile corrugation, which appears as an instability, in analogy to the way a clustering instability leads to a traffic jam. Such local amplification of heat and profile corrugations can lead to the formation of E × B staircases. The scale length that gives the maximum growth rate falls in the mesoscale range and is comparable to the staircase step spacing. Present address: IAS and RIAM, Kyushu University, Japan.

  10. A scenario-based study on information flow and collaboration patterns in disaster management.

    Science.gov (United States)

    Sagun, Aysu; Bouchlaghem, Dino; Anumba, Chimay J

    2009-04-01

    Disaster management (DM) is a continuous, highly collaborative process involving governments, DM organisations, responders, the construction sector, and the general public. Most research approaches to DM include the development of information and communication technologies (ICT) to support the collaboration process rather than the creation of a collaboration process to provide information flows and patterns. An Intelligent Disaster Collaboration System (IDCS) is introduced in this paper as a conceptual model to integrate ICT into DM and the mitigation process and to enhance collaboration. The framework is applicable to the collaboration process at the local, regional and national levels. Within this context, the deployment of ICT tools in DM is explored and scenario-based case studies on flooding and terrorism--examples of natural and human-induced disasters, respectively--are presented. Conclusions are drawn regarding the differences found in collaboration patterns and ICT used during natural and human-induced disasters and the differences between currently available ICT and proposed ICT.

  11. Inertia-induced dendriticlike patterns in lifting Hele-Shaw flows

    Science.gov (United States)

    Anjos, Pedro H. A.; Dias, Eduardo O.; Miranda, José A.

    2017-01-01

    The lifting Hele-Shaw cell problem is a variant of the classical constant-gap Hele-Shaw situation in which the cell gap width is time dependent. Experiments on Newtonian fluid flows in lifting Hele-Shaw cells with large lifting velocities reveal the development of dendriticlike fingered structures that compete among themselves. The usual Darcy law description of the problem, where inertial effects are neglected, has not been able to explain the origin of these competing sidebranched patterns. In this work we use a generalized Darcy law and a perturbative mode-coupling theory to investigate the impact of inertia on the pattern-forming dynamics of the system. Two main results are deduced: Inertia induces a mechanism for finger sidebranching formation and favors the intensification of finger competition events.

  12. Effect of bank slope on the flow patterns in river intakes

    Institute of Scientific and Technical Information of China (English)

    SEYEDIAN Seyed Morteza; BAJESTAN Mahmood Shafai; FARASATI Masoomeh

    2014-01-01

    In this work, we studied the dimensions of stream tube in the vertical as well as inclined bank conditions. Data were co-llected from both a physical model and a 3-D numerical model (SSIIM 2). Equations for predicting stream tube dimensions were presented and compared with existing formulae. In comparison with vertical bank, it is found that inclining bank causes the bottom stream tube width to be greater than at the surface. The strength of secondary current formed at the entrance of branch channel is reduced. These changes in flow pattern can reduce the amount of sediment delivery into the intake.

  13. Flow patterns in a slurry-bubble-column reactor under reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Toselane, B.A.; Brown, D.M.; Zou, B.S.; Dudukovic, M.P. [Washington Univ., St. Louis, MO (United States)

    1995-12-31

    The gas and liquid radioactive tracer response curves obtained in an industrial bubble column reactor of height to diameter ratio of 10 are analyzed and the suitability of the axial dispersion model for interpretation of the results is discussed. The relationship between the tracer concentration distribution and measured detector response of the soluble gas tracer (Ar-41) is possibly dominated by the dissolved gas. The one dimensional axial dispersion model cannot match all the experimental observations well and the flow pattern of the undissolved gas cannot be determined with certainty.

  14. Characterization of flow pattern transitions for horizontal liquid-liquid pipe flows by using multi-scale distribution entropy in coupled 3D phase space

    Science.gov (United States)

    Zhai, Lu-Sheng; Zong, Yan-Bo; Wang, Hong-Mei; Yan, Cong; Gao, Zhong-Ke; Jin, Ning-De

    2017-03-01

    Horizontal oil-water two-phase flows often exist in many industrial processes. Uncovering the dynamic mechanism of the flow pattern transition is of great significance for modeling the flow parameters. In this study we propose a method called multi-scale distribution entropy (MSDE) in a coupled 3D phase space, and use it to characterize the flow pattern transitions in horizontal oil-water two-phase flows. Firstly, the proposed MSDE is validated with Lorenz system and ARFIMA processes. Interestingly, it is found that the MSDE is dramatically associated with the cross-correlations of the coupled time series. Then, through conducting the experiment of horizontal oil-water two-phase flows, the upstream and downstream flow information is collected using a conductance cross-correlation velocity probe. The coupled cross-correlated signals are investigated using the MSDE method, and the results indicate that the MSDE is an effective tool uncovering the complex dynamic behaviors of flow pattern transitions.

  15. Pattern formation of reaction-diffusion system having self-determined flow in the amoeboid organism of Physarum plasmodium

    CERN Document Server

    Yamada, H; Ito, M

    1998-01-01

    The amoeboid organism, the plasmodium of Physarum polycephalum, behaves on the basis of spatio-temporal pattern formation by local contraction-oscillators. This biological system can be regarded as a reaction-diffusion system which has spatial interaction by active flow of protoplasmic sol in the cell. Paying attention to the physiological evidence that the flow is determined by contraction pattern in the plasmodium, a reaction-diffusion system having self-determined flow arises. Such a coupling of reaction-diffusion-advection is a characteristic of the biological system, and is expected to relate with control mechanism of amoeboid behaviours. Hence, we have studied effects of the self-determined flow on pattern formation of simple reaction-diffusion systems. By weakly nonlinear analysis near a trivial solution, the envelope dynamics follows the complex Ginzburg-Landau type equation just after bifurcation occurs at finite wave number. The flow term affects the nonlinear term of the equation through the critic...

  16. The golden-mean surface pattern to enhance flow mixing in micro-channel.

    Science.gov (United States)

    Wang, J F; Liu, Y; Xu, Y S

    2009-04-01

    Mixing of analytes and reagents in microfluidic devices is often crucial to the effective functioning of lab-on-a-chip. It is possible to affect the mixing in microfluidics by intelligently controlling the thermodynamic and chemical properties of the substrate surface. Numerous studies have shown that the phase behavior of mixtures is significantly affected by surface properties of microfluidics. For example, the phase separation between the fluids can be affected by heterogeneous patterns on the substrate. The patterned substrate can offer an effective means to control fluid behavior and in turn to enhance mixing. The golden mean is a ratio that is present in the growth patterns of many biological systems--the spiral formed by a shell or the curve of a fern, for example. The golden mean or golden section was derived by the ancient Greeks. Like "pi" the golden mean ratio is an irrational number 1.618, or (square root{5} + 1) / 2. It was found that the golden mean was an optimum ratio in natural convection heat transfer problem (Liu and Phan-Thien, Numer Heat Transf 37:613-630, 2000). In this study, we numerically studied the effect of optimum surface pattern on mixing in a micro channel and found that the flow oscillation and chaotic mixing were enhanced apparently when the ratio of hydrophobic and hydrophilic boundary follows the golden mean.

  17. Knowledge Discovery for Classification of Three-Phase Vertical Flow Patterns of Heavy Oil from Pressure Drop and Flow Rate Data

    Directory of Open Access Journals (Sweden)

    Adriane B. S. Serapião

    2013-01-01

    Full Text Available This paper focuses on the use of artificial intelligence (AI techniques to identify flow patterns acquired and recorded from experimental data of vertical upward three-phase pipe flow of heavy oil, air, and water at several different combinations, in which water is injected to work as the continuous phase (water-assisted flow. We investigate the use of data mining algorithms with rule and tree methods for classifying real data generated by a laboratory scale apparatus. The data presented in this paper represent different heavy oil flow conditions in a real production pipe.

  18. Computational Analysis of Intra-Ventricular Flow Pattern Under Partial and Full Support of BJUT-II VAD

    Science.gov (United States)

    Zhang, Qi; Gao, Bin; Chang, Yu

    2017-01-01

    Background Partial support, as a novel support mode, has been widely applied in clinical practice and widely studied. However, the precise mechanism of partial support of LVAD in the intra-ventricular flow pattern is unclear. Material/Methods In this study, a patient-specific left ventricular geometric model was reconstructed based on CT data. The intra-ventricular flow pattern under 3 simulated conditions – “heart failure”, “partial support”, and “full support” – were simulated by using fluid-structure interaction (FSI). The blood flow pattern, wall shear stress (WSS), time-average wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) were calculated to evaluate the hemodynamic effects. Results The results demonstrate that the intra-ventricular flow pattern is significantly changed by the support level of BJUT-II VAD. The intra-ventricular vortex was enhanced under partial support and was eliminated under full support, and the high OSI and RRT regions changed from the septum wall to the cardiac apex. Conclusions In brief, the support level of the BJUT-II VAD has significant effects on the intra-ventricular flow pattern. The partial support mode of BJUT-II VAD can enhance the intra-ventricular vortex, while the distribution of high OSI and RRT moved from the septum wall to the cardiac apex. Hence, the partial support mode of BJUT-II VAD can provide more benefit for intra-ventricular flow pattern. PMID:28239142

  19. Computational Analysis of Intra-Ventricular Flow Pattern Under Partial and Full Support of BJUT-II VAD.

    Science.gov (United States)

    Zhang, Qi; Gao, Bin; Chang, Yu

    2017-02-27

    BACKGROUND Partial support, as a novel support mode, has been widely applied in clinical practice and widely studied. However, the precise mechanism of partial support of LVAD in the intra-ventricular flow pattern is unclear. MATERIAL AND METHODS In this study, a patient-specific left ventricular geometric model was reconstructed based on CT data. The intra-ventricular flow pattern under 3 simulated conditions - "heart failure", "partial support", and "full support" - were simulated by using fluid-structure interaction (FSI). The blood flow pattern, wall shear stress (WSS), time-average wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) were calculated to evaluate the hemodynamic effects. RESULTS The results demonstrate that the intra-ventricular flow pattern is significantly changed by the support level of BJUT-II VAD. The intra-ventricular vortex was enhanced under partial support and was eliminated under full support, and the high OSI and RRT regions changed from the septum wall to the cardiac apex. CONCLUSIONS In brief, the support level of the BJUT-II VAD has significant effects on the intra-ventricular flow pattern. The partial support mode of BJUT-II VAD can enhance the intra-ventricular vortex, while the distribution of high OSI and RRT moved from the septum wall to the cardiac apex. Hence, the partial support mode of BJUT-II VAD can provide more benefit for intra-ventricular flow pattern.

  20. Thinking Aloud While Solving a Stock-Flow Task: Surfacing the Correlation Heuristic and Other Reasoning Patterns

    NARCIS (Netherlands)

    Korzilius, H.P.L.M.; Raaijmakers, S.F.J.M.; Rouwette, E.A.J.A.; Vennix, J.A.M.

    2014-01-01

    In the literature, it is assumed that individuals, while performing stock-flow tasks, often use a correlation heuristic, a form of pattern matching in which they think that the behavior of the stock resembles the (net) flow. To investigate this assumption and to increase our insight in the actual

  1. CSTR-UASB两相厌氧系统对制糖工业废水的降解%The effect of CSTR-UASB two-phase anaerobic system on degradation of sugar wastewater

    Institute of Scientific and Technical Information of China (English)

    黄志

    2016-01-01

    CSTR-UASB两相厌氧反应器的原理如下:CSTR采用复合红糖水作为发酵底物,其液体的最终产品是UASB反应底物.污水处理厂污泥作为反应器的起始污泥.反应器运行稳定后,我们可以通过改变有机负荷对两相厌氧CSTR-UASB系统的影响.结果表明,厌氧污泥产氢能力将继续上升六个阶段,有机负荷的含量逐渐提高,并在有机负荷达到最大,产氢能力达到最大.随着有机负荷的增加,甲烷的甲烷量先增大后减小.我们发现,有机负荷为2 8公斤/(mI米3?D)同时,COD的总去除率达到最大值.因此,CSTR-UASB两相厌氧系统对红糖废水的降解,使在废s水再利用方面的差异.

  2. Effects of cohesion on the flow patterns of granular materials in spouted beds

    Science.gov (United States)

    Zhu, Runru; Li, Shuiqing; Yao, Qiang

    2013-02-01

    Two-dimensional spouted bed, capable to provide both dilute granular gas and dense granular solid flow patterns in one system, was selected as a prototypical system for studying granular materials. Effects of liquid cohesion on such kind of complex granular patterns were studied using particle image velocimetry. It is seen that the addition of liquid oils by a small fraction of 10-3-10-2 causes a remarkable narrowing (about 15%) of the spout area. In the dense annulus, as the liquid fraction increases, the downward particle velocity gradually decreases and approaches a minimum where, at a microscopic grain scale, the liquid bridge reaches spherical regimes with a maximum capillarity. Viscous lubrication effect is observed at a much higher fraction but is really weak with respect to the capillary effect. In the dilute spout, in contrast to the dry grains, the wet grains have a lightly smaller acceleration in the initial 1/3 of the spout, but have a dramatically higher acceleration in the rest of the spout. We attribute the former to the additional work needed to overcome interparticle cohesion during particle entrainment at the spout-annulus interface. Then, using mass and momentum balances, the latter is explained by the relative higher drag force resulting from both higher gas velocities and higher voidages due to spout narrowing in the wet system. The experimental findings will provide useful data for the validation of discrete element simulation of cohesive granular-fluid flows.

  3. Numerical Investigation of Liquid Flow through Micro-channels with Post Patterned Super-hydrophobic Walls

    Science.gov (United States)

    Amin, A.; Maynes, D.; Webb, B. W.

    2009-11-01

    We numerically investigate the effect of post patterned super-hydrophobic surfaces on the drag reduction for laminar liquid flow through micro-channels. Hydrophobic surfaces exhibiting micro-scale structures can significantly reduce the liquid-solid contact area resulting in reduced surface friction. The effects of cavity fraction (the ratio of cavity area to total surface area) and relative module width (ratio of post/cavity repeating length to channel hydraulic diameter) on the slip-length and on the Darcy friction factor-Reynolds number product, fRe, were explored numerically for the post structured hydrophobic walls. The cavity fraction and relative module width vary from 0.5 to 0.9998 and from 0.01 to 1.5, respectively. In general, as both cavity fraction and relative module width increase fRe decreases. The present results are compared with those for surfaces exhibiting rib/cavity patterns that are parallel and perpendicular to the flow direction. At high cavity fractions the post/cavity structuring produces larger slip-length and greater reduction in fRe than either parallel or perpendicular rib/cavity structures. The results are also compared with scaling laws previously published in the literature.

  4. Imaging wet granules with different flow patterns by electrical capacitance tomography and microwave tomography

    Science.gov (United States)

    Wang, H. G.; Zhang, J. L.; Ramli, M. F.; Mao, M. X.; Ye, J. M.; Yang, W. Q.; Wu, Z. P.

    2016-11-01

    The moisture content of granules in fluidised bed drying, granulation and coating processes can typically be between 1%~25%, resulting in the change of permittivity and conductivity during the processes. Electrical capacitance tomography (ECT) has been used for this purpose, but has a limit because too much water can cause a problem in capacitance measurement. Considering that microwave tomography (MWT) has a wide range of frequency (1~2.5 GHz) and can be used to measure materials with high permittivity and conductivity, the objective of this research is to combine ECT and MWT together to investigate the solids concentration with different moisture content and different flow patterns. The measurement results show that both ECT and MWT are functions of moisture content as well as flow patterns, and their measurements are complementary to each other. This is the first time that these two tomography modalities have been combined together and applied to image the complex solids distribution. The obtained information may be used for the process control of fluidised bed drying, granulation and coating to improve operation efficiency.

  5. Exploring Learners' Sequential Behavioral Patterns, Flow Experience, and Learning Performance in an Anti-Phishing Educational Game

    Science.gov (United States)

    Sun, Jerry Chih-Yuan; Kuo, Cian-Yu; Hou, Huei-Tse; Lin, Yu-Yan

    2017-01-01

    The purposes of this study were to provide a game-based anti-phishing lesson to 110 elementary school students in Taiwan, explore their learning behavioral patterns, and investigate the effects of the flow states on their learning behavioral patterns and learning achievement. The study recorded behaviour logs, and applied a pre- and post-test on…

  6. Exploring Learners' Sequential Behavioral Patterns, Flow Experience, and Learning Performance in an Anti-Phishing Educational Game

    Science.gov (United States)

    Sun, Jerry Chih-Yuan; Kuo, Cian-Yu; Hou, Huei-Tse; Lin, Yu-Yan

    2017-01-01

    The purposes of this study were to provide a game-based anti-phishing lesson to 110 elementary school students in Taiwan, explore their learning behavioral patterns, and investigate the effects of the flow states on their learning behavioral patterns and learning achievement. The study recorded behaviour logs, and applied a pre- and post-test on…

  7. Comparison of CSTR and UASB reactor configuration for the treatment of sulfate rich wastewaters under acidifying conditions

    NARCIS (Netherlands)

    Lopes, S.I.C.; Dreissen, C.; Capela, M.I.; Lens, P.N.L.

    2008-01-01

    The effects of lowering the operational pH from 6 to 5 on mesophilic (30 degrees C) sulfate reduction during the acidification of sucrose at an organic loading rate of 5 gCOD(1(reactor)d)(-1) and at a COD/SO42- ratio of 4 were evaluated in a CSTR and in a UASB reactor. The HRT was 24 h and 10 h, res

  8. Oscillation in the Kmno 4NH 2CH 2COOHH 3PO 4 Cstr system

    Science.gov (United States)

    Li, Hexing; Huang, Xiaojun; Deng, Jingfa

    1996-08-01

    A novel chemical oscillating reaction in the KMnO 4NH 2CH 2COOHH 3PO 4 CSTR system in the presence and absence of Ag + has been described. The reaction kinetics in a closed Mn0 4-NH 2CH 2COOHH 3PO 4 system has been analyzed and a possible mechanism has been proposed. The catalytic effect of Ag + in the above reaction has also been studied.

  9. Experimental analysis of the flow pattern of a pump turbine model in pump mode

    Science.gov (United States)

    Guggenberger, Mark; Senn, Florian; Jaberg, Helmut; Gehrer, Arno; Sallaberger, Manfred; Widmer, Christian

    2016-11-01

    Reversible pump turbines are the only means to store primary energy in an highly efficient way. Within a short time their operation can be switched between the different operational regimes thus enhancing the stabilization of the electric grid. These qualities in combination with the operation even at off-design conditions offer a high flexibility to the energy market. However, pump turbines pass through operational regimes where their behaviour becomes unstable. One of these effects occurs when the flowrate is decreased continuously down to a minimum. This point is the physical limitation of the pump operation and is very difficult to predict properly by numerical design without a model test. The purpose of the present study is to identify the fluid mechanical phenomena leading to the occurrence of instabilities of pump turbines in pump mode. A reduced scale model of a ANDRITZ pump turbine was installed on a 4-quadrant test rig for the experimental investigation of unstable conditions in pump mode. The performed measurements are based on the IEC60193-standard. Characteristic measurements at a single guide vane opening were carried out to get a detailed insight into the instabilities in pump mode. The interaction between runner and guide vane was analysed by Particle Image Velocimetry. Furthermore, high-speed visualizations of the suction side part load flow and the suction recirculation were performed. Like never before the flow pattern in the draft tube cone became visible with the help of a high-speed camera by intentionally caused cavitation effects which allow a qualitative view on the flow pattern in the draft tube cone. Suction recirculation is observed in form of single vortices separating from each runner blade and stretching into the draft tube against the main flow direction. To find an explanation for the flow phenomena responsible for the appearance of the unstable head curve also characteristic velocity distributions on the pressure side were combined

  10. A quantitative study of CSF pulsatile flow in normal pressure hydrocephalus; An analysis of flow patterns before and after a shunting procedure using cine MR phase imaging

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Shinji; Makabe, Tetsuo; Itoh, Takahiko (Okayama Univ. (Japan). School of Medicine) (and others)

    1992-06-01

    In the previous report, we described the visualization and quantitative analysis of a normal CSF pulsatile flow using cine MR phase imaging. In the present study, CSF flow velocities were measured in patients with normal pressure hydrocephalus (NPH) before and after a shunting procedure. All of the healthy subjects showed a similar flow pattern in the time-velocity flow profiles (TVFP). However, patients with NPH showed a variable pattern of TVFP and could be divided into the following four types: Type 0: the CSF flow pattern was similar to that of the healthy subjects. Type I: the caudal peak flow was delayed more than 190 msec on TVFP. Type II: the caudal peak flow was not apparent, but the CSF flow through the aqueduct was remarkable on phase images. Type III: the amplitude of TVFP was very small, and no CSF flow through the aqueduct was identified. The patients with Type III TVFP showed significantly lower NPH scores. The lumbar CSF pressures tended to be high in the patients with Type III TVFP, but nevertheless failed to reach a statistically significant level. The amplitude of TVFP increased in the patients who improved clinically after the shunting procedure. Some of the Type III patients changed into Type II, I, and 0; also, one of the Type II patients changed into a Type I patients after the shunting procedure. We conclude that cine MR phase imaging is useful for analyzing the CSF flow of the patients with NPH before and after the shunting procedure as well as for evaluating shunt patency. (author).

  11. Anaerobic digestion of blackwater from vacuum toilets and kitchen refuse in a continuous stirred tank reactor (CSTR).

    Science.gov (United States)

    Wendland, C; Deegener, S; Behrendt, J; Toshev, P; Otterpohl, R

    2007-01-01

    The objective of this research was mesophilic anaerobic digestion of blackwater from vacuum toilets (BW) and kitchen refuse (KR) in a CSTR within an ecological sanitation system. A detailed investigation of the BW characteristics was carried out. Research on anaerobic digestion was performed with CSTR of 101 volume at HRT of 10, 15 and 20 days. The digestion of BW at 20 days HRT showed stable performance without inhibition effects, in spite of relatively high ammonium concentrations. The removal of total and particulate COD was 61% and 53%, respectively, and the methane yield 10/CH4/cap/day. The addition of kitchen refuse (KR) improved the performance of the CSTR in terms of COD removal efficiency and methane yield. At 20 days HRT the removal of total and particulate COD increased up to 71% and 67%, respectively, and the methane yield to 27/CH4/cap/day. The results at 15 days HRT showed similar performance. At HRT of 10 days, the anaerobic treatment was limited but reached steady state conditions at higher VFA concentrations in the effluent, with a decrease of COD removal of 30 to 33% and of methane yields of 19 to 21%.

  12. Coupled Effects of Hyporheic Flow Structure and Metabolic Pattern on Reach-scale Nutrient Uptake

    Science.gov (United States)

    Li, A.; Aubeneau, A. F.; Bolster, D.; Tank, J. L.; Packman, A. I.

    2015-12-01

    Co-injections of conservative tracers and nutrients are commonly used to assess net reach-scale nutrient transformation rates and benthic/hyporheic uptake parameters. However, little information is available on spatial metabolic patterns in the benthic and hyporheic regions. Based on observations from real systems, we used particle tracking simulations to explore the effects of localized metabolism on estimates of reach-scale nutrient uptake rates. Metabolism locally depletes nutrient concentrations relative to conservative tracers, causing their concentration profiles of injected nutrients and conservative tracers to diverge. At slow rates of hyporheic exchange relative to rates of metabolism, overall hyporheic nutrient uptake is limited by delivery from the stream, and effective reach-scale nutrient uptake parameters will be controlled by the hyporheic exchange rate. At high rates of hyporheic exchange relative to rates of metabolism, the injected tracer can propagate beyond regions of high microbial activity, which commonly occur near the streambed surface. In this case, the injected tracer may not adequately capture timescales of nutrient replenishment in the most bioactive regions. Reach-scale nutrients uptake rate increases with increasing heterogeneity in local metabolic patterns, altering the shape of breakthrough curves downstream. More observations of hyporheic rates and metabolic patterns are needed to understand how flow heterogeneity and reaction heterogeneity interact to control nutrient dynamics at reach-scale.

  13. Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model

    Science.gov (United States)

    Ryo, Masahiro; Iwasaki, Yuichi; Yoshimura, Chihiro; Saavedra V., Oliver C.

    2015-01-01

    Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov–Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities. PMID:26207997

  14. Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model.

    Directory of Open Access Journals (Sweden)

    Masahiro Ryo

    Full Text Available Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4 and the Kolmogorov-Smirnov test (α = 0.05 by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively. These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities.

  15. Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model.

    Science.gov (United States)

    Ryo, Masahiro; Iwasaki, Yuichi; Yoshimura, Chihiro; Saavedra V, Oliver C

    2015-01-01

    Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov-Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities.

  16. Functional morphology and patterns of blood flow in the heart of Python regius.

    Science.gov (United States)

    Starck, J Matthias

    2009-06-01

    Brightness-modulated ultrasonography, continuous-wave Doppler, and pulsed-wave Doppler-echocardiography were used to analyze the functional morphology of the undisturbed heart of ball pythons. In particular, the action of the muscular ridge and the atrio-ventricular valves are key features to understand how patterns of blood flow emerge from structures directing blood into the various chambers of the heart. A step-by-step image analysis of echocardiographs shows that during ventricular diastole, the atrio-ventricular valves block the interventricular canals so that blood from the right atrium first fills the cavum venosum, and blood from the left atrium fills the cavum arteriosum. During diastole, blood from the cavum venosum crosses the muscular ridge into the cavum pulmonale. During middle to late systole the muscular ridge closes, thus prohibiting further blood flow into the cavum pulmonale. At the same time, the atrio-ventricular valves open the interventricular canal and allow blood from the cavum arteriosum to flow into the cavum venosum. In the late phase of ventricular systole, all blood from the cavum pulmonale is pressed into the pulmonary trunk; all blood from the cavum venosum is pressed into both aortas. Quantitative measures of blood flow volume showed that resting snakes bypass the pulmonary circulation and shunt about twice the blood volume into the systemic circulation as into the pulmonary circulation. When digesting, the oxygen demand of snakes increased tremendously. This is associated with shunting more blood into the pulmonary circulation. The results of this study allow the presentation of a detailed functional model of the python heart. They are also the basis for a functional hypothesis of how shunting is achieved. Further, it was shown that shunting is an active regulation process in response to changing demands of the organism (here, oxygen demand). Finally, the results of this study support earlier reports about a dual pressure

  17. Flow patterns generated by vibrations in weightlessness in binary mixture with Soret effect.

    Science.gov (United States)

    Shevtsova, Valentina; Melnikov, Denis; Gaponenko, Yuri; Lyubimova, Tatyana; Mialdun, Aliaksandr; Sechenyh, Vitaliy

    2012-07-01

    Vibrational convection refers to the specific flows that appear when a fluid with density gradient is subjected to external vibration. The density gradient may result from the inhomogeneity of temperature or composition. The study of vibrational impact on fluids has fundamental and applied importance. In weightlessness, vibrational convection is an additional way of transporting heat and matter similar to thermo- and solutocapillary convection. The response of the fluid to external forcing depends on the frequency of vibration. The case of small amplitude and high frequency vibration (when the period is much smaller than the characteristic viscous and heat (mass) diffusion times) is of special interest. In this case, the mean flow can be observed in the system, which describes the non-linear response of the fluid to a periodic excitation. The mean flow is most pronounced in the absence of other external forces (in particular, absence of static gravity). The experiment IVIDIL (Influence of Vibration on Diffusion in Liquids) has been conducted on the ISS during more than 3 months in 2009-2010. In the experimental liquids the density changes due to both the temperature and composition. 55 experimental runs of IVIDIL provided rich variety of valuable information about behavior of the liquid in weightlessness which is released with time, [1-3]. The current results provide experimental and numerical evidence of richness of flow patterns and their classification. References: 1. Shevtsova V., Mialdun A., Melnikov D., Ryzhkov I., Gaponenko Y., Saghir Z., Lyubimova T., Legros J.C., IVIDIL experiment onboard ISS: thermodiffusion in presence of controlled vibrations, Comptes Rendus Mecanique, 2011, 339, 310-317 2. Shevtsova V., Lyubimova T., Saghir Z. , Melnikov D., Gaponenko Y. , Sechenyh V. , Legros J.C. , Mialdun A., IVIDIL: on-board g-jitters and diffusion controlled phenomena; Journal of Physics: Conference Series, 2011, 327, 012031 3. Mazzoni S., Shevtsova V., Mialdun A

  18. Debris flow prevention pattern in national parks-Taking the world natural heritage Jiuzhaigou as an example

    Institute of Scientific and Technical Information of China (English)

    CUI; Peng; LIU; Suqing; TANG; Bangxing; CHEN; Xiaoqing

    2003-01-01

    With the development of the ecological tourism, how to control debris flow in national parks becomes an urgent problem. The characteristics of prevention of the debris flow in the areas are systematically studied, and a scientific strategy is introduced for dealing with debris flows. In term of the activity attribute of the debris flow and objects protected in Jiuzhaigou, some methods are proposed to arrange the projects of hazard mitigation, and finally an approach is established to carry out the technology in the control of the debris flow scientifically, reasonably and feasibly. Integrating the aforesaid strategy with methods, the pattern of prevention and countermeasures of the debris flow has been theorized, in this way the mitigation hazards engineering is in harmony with the natural view and combined with the ecology. The prevention pattern of the debris flow in national parks is divergent from those in other areas such as towns, traffic lines, and farmland.After the successful application of the pattern in the Jiuzhaigou National Park, it effectively controls debris flows and achieves the expected target, such as conserving the landscape resource, sustaining ecological environment, and securing the visitors and residents.

  19. Influence of anatomical dominance and hypertension on coronary conduit arterial and microcirculatory flow patterns: a multiscale modeling study.

    Science.gov (United States)

    Mynard, Jonathan P; Smolich, Joseph J

    2016-07-01

    Coronary hemodynamics are known to be affected by intravascular and extravascular factors that vary regionally and transmurally between the perfusion territories of left and right coronary arteries. However, despite clinical evidence that left coronary arterial dominance portends greater cardiovascular risk, relatively little is known about the effects of left or right dominance on regional conduit arterial and microcirculatory blood flow patterns, particularly in the presence of systemic or pulmonary hypertension. We addressed this issue using a multiscale numerical model of the human coronary circulation situated in a closed-loop cardiovascular model. The coronary model represented left or right dominant anatomies and accounted for transmural and regional differences in vascular properties and extravascular compression. Regional coronary flow dynamics of the two anatomical variants were compared under normotensive conditions, raised systemic or pulmonary pressures with maintained flow demand, and after accounting for adaptations known to occur in acute and chronic hypertensive states. Key findings were that 1) right coronary arterial flow patterns were strongly influenced by dominance and systemic/pulmonary hypertension; 2) dominance had minor effects on left coronary arterial and all microvascular flow patterns (aside from mean circumflex flow); 3) although systemic hypertension favorably increased perfusion pressure, this benefit varied regionally and transmurally and was offset by increased left ventricular and septal flow demands; and 4) pulmonary hypertension had a substantial negative effect on right ventricular and septal flows, which was exacerbated by greater metabolic demands. These findings highlight the importance of interactions between coronary arterial dominance and hypertension in modulating coronary hemodynamics.

  20. Three-dimensional flow structure and patterns of bed shear stress in an evolving compound meander bend

    Science.gov (United States)

    Engel, Frank; Rhoads, Bruce L.

    2016-01-01

    Compound meander bends with multiple lobes of maximum curvature are common in actively evolving lowland rivers. Interaction among spatial patterns of mean flow, turbulence, bed morphology, bank failures and channel migration in compound bends is poorly understood. In this paper, acoustic Doppler current profiler (ADCP) measurements of the three-dimensional (3D) flow velocities in a compound bend are examined to evaluate the influence of channel curvature and hydrologic variability on the structure of flow within the bend. Flow structure at various flow stages is related to changes in bed morphology over the study timeframe. Increases in local curvature within the upstream lobe of the bend reduce outer bank velocities at morphologically significant flows, creating a region that protects the bank from high momentum flow and high bed shear stresses. The dimensionless radius of curvature in the upstream lobe is one-third less than that of the downstream lobe, with average bank erosion rates less than half of the erosion rates for the downstream lobe. Higher bank erosion rates within the downstream lobe correspond to the shift in a core of high velocity and bed shear stresses toward the outer bank as flow moves through the two lobes. These erosion patterns provide a mechanism for continued migration of the downstream lobe in the near future. Bed material size distributions within the bend correspond to spatial patterns of bed shear stress magnitudes, indicating that bed material sorting within the bend is governed by bed shear stress. Results suggest that patterns of flow, sediment entrainment, and planform evolution in compound meander bends are more complex than in simple meander bends. Moreover, interactions among local influences on the flow, such as woody debris, local topographic steering, and locally high curvature, tend to cause compound bends to evolve toward increasing planform complexity over time rather than stable configurations.

  1. The Effect of Sudden Change in Pipe Diameter on Flow Patterns of Air-Water Two-Phase Flow in Vertical Pipe (Ⅱ) Sudden-Expansion Cross-Section

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this companion paper, flow patterns in the upstream and downstream tubes of a sudden-expansion cross-section (SECS) in a vertical straight pipe were presented. The effect of SECS on flow patterns upstream and downstream was analyzed by comparing with flow patterns in uniform cross-section vertical tubes. It is found the effect is great. There exist great instabilities of two-phase flow in the neighboring areas of the SECS both downstream and upstream.

  2. CFD optimization of continuous stirred-tank (CSTR) reactor for biohydrogen production.

    Science.gov (United States)

    Ding, Jie; Wang, Xu; Zhou, Xue-Fei; Ren, Nan-Qi; Guo, Wan-Qian

    2010-09-01

    There has been little work on the optimal configuration of biohydrogen production reactors. This paper describes three-dimensional computational fluid dynamics (CFD) simulations of gas-liquid flow in a laboratory-scale continuous stirred-tank reactor used for biohydrogen production. To evaluate the role of hydrodynamics in reactor design and optimize the reactor configuration, an optimized impeller design has been constructed and validated with CFD simulations of the normal and optimized impeller over a range of speeds and the numerical results were also validated by examination of residence time distribution. By integrating the CFD simulation with an ethanol-type fermentation process experiment, it was shown that impellers with different type and speed generated different flow patterns, and hence offered different efficiencies for biohydrogen production. The hydrodynamic behavior of the optimized impeller at speeds between 50 and 70 rev/min is most suited for economical biohydrogen production.

  3. Investigation of journal orbit and flow pattern in a dynamically loaded journal bearing

    DEFF Research Database (Denmark)

    Christiansen, Christian Kim; Walther, Jens Honore; Klit, Peder

    2017-01-01

    A hydrodynamic journal bearing has been investigated using both the traditional two-dimensional (2D) Reynolds equation, and the full solution being the three-dimensional (3D) Navier-Stokes equations. The two approaches are compared by performing an investigation of two inlet groove designs......: the axial and the circumferential groove, respectively, on a bearing with length-to-diameter ratio of 0.5 exposed to a sinusoidal load pattern. Pressure distributions, journal orbits and frictional losses are compared. The modelling of grooves by pressure boundary conditions versus geometric conditions...... is examined. It is investigated if the presence of a groove increases frictional losses and the increase relates to groove dimensions. Furthermore, the influence of the groove design on the flow field is studied using the 3D solution....

  4. Two-Dimensional River Flow Patterns Observed with a Pair of UHF Radar System

    Directory of Open Access Journals (Sweden)

    Yidong Hou

    2017-01-01

    Full Text Available A pair of ultrahigh-frequency (UHF radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329–339 MHz and 341–351 MHz. The adoption of direct radio frequency (RF sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.

  5. Evolution of dislocation patterns and its application in prediction of flow stress

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhimin; SUN Yanrui

    2004-01-01

    The feature of dislocation patterns generated in plastic deformation is the ordered structure of alternative appearance of high and low dislocation density zones. With regard to the system of edge and screw dislocations, a nonlinear partial differential equation (eq. (13) in the text)including high order terms is established based on the reaction-diffusion equation. The contribution of cross slip of screw dislocations to the edge dislocation density is also considered in the analysis. The established equation has the typical feature of nonlinear system. Therefore, one does not need to deal with the complex expressions of the reaction and generation terms for dislocations. By theoretical analysis, the distance between adjacent high dislocation density zones (cell size or distance between cell walls) is obtained. By using this relationship, the flow stresses of ultrafine grained (UFG)copper and aluminum are predicted. The calculated results are well consistent with the experimental.

  6. Heat Flow Pattern and Thermal Resistance Modeling of Anisotropic Heat Spreaders

    Science.gov (United States)

    Falakzaadeh, F.; Mehryar, R.

    2017-01-01

    To ensure safe operating temperatures of the ever smaller heat generating electronic devices, drastic measures should be taken. Heat spreaders are used to increase surface area, by spreading the heat without necessarily transferring it to the ambient in the first place. The heat flow pattern is investigated in heat spreaders and the fundamental differences regarding how heat conducts in different materials is addressed. Isotropic materials are compared with anisotropic ones having a specifically higher in-plane thermal conductivity than through plane direction. Thermal resistance models are proposed for anisotropic and isotropic heat spreaders in compliance with the order of magnitude of dimensions used in electronics packaging. After establishing thermal resistance models for both the isotropic and anisotropic cases, numerical results are used to find a correlation for predicting thermal resistance in anisotropic heat spreaders with high anisotropy ratios.

  7. 突变管段三相流流型研究%The Study on Flow Pattern of Three-Phase Flow in Mutation Pipe

    Institute of Scientific and Technical Information of China (English)

    常方圆; 马贵阳; 安利姣; 李泽; 孙淼

    2015-01-01

    Due to the oil-gas-water three-phase flow is extremely complex,the three-phase hybrid interface is weak of stability,different delivery conditions exist a variety of flow patterns.Using the VOF model simulation,the mock object was oil-gas-water three-phase flow in mutation tube,studying the fluid flow in pipe when the parameters(volume gas fraction,oil viscosity and velocity)was different,thus it gotten the corresponding phase distribution nephogram.Through analyzing the results showed that the gas volume fraction and velocity had great effect on mutiphase flow pattern.The effect of crude oil viscosity on flow patterns was not very obvious.The size of the pipe diameter also affected the flow pattern.%油气水三相流动极其复杂,三相之间的混合界面稳定性较弱,因此在不同的输送条件下存在多种流型。使用 VOF 模型,以突变管段内油气水三相流为模拟对象,在气体体积分数、原油黏度及流动速度等参数不同的条件下,对流体在管内的流动进行了模拟,得到了相应的相分布云图。研究结果表明,气体体积分数及流速对多相流流型具有很大的影响,而原油的黏度对流型的影响不是很明显。

  8. AN INTELLIGENT CONTROL SYSTEM BASED ON RECURRENT NEURAL FUZZY NETWORK AND ITS APPLICATION TO CSTR

    Institute of Scientific and Technical Information of China (English)

    JIA Li; YU Jinshou

    2005-01-01

    In this paper, an intelligent control system based on recurrent neural fuzzy network is presented for complex, uncertain and nonlinear processes, in which a recurrent neural fuzzy network is used as controller (RNFNC) to control a process adaptively and a recurrent neural network based on recursive predictive error algorithm (RNNM) is utilized to estimate the gradient information (ey)/(e)u for optimizing the parameters of controller.Compared with many neural fuzzy control systems, it uses recurrent neural network to realize the fuzzy controller. Moreover, recursive predictive error algorithm (RPE) is implemented to construct RNNM on line. Lastly, in order to evaluate the performance of theproposed control system, the presented control system is applied to continuously stirred tank reactor (CSTR). Simulation comparisons, based on control effect and output error,with general fuzzy controller and feed-forward neural fuzzy network controller (FNFNC),are conducted. In addition, the rates of convergence of RNNM respectively using RPE algorithm and gradient learning algorithm are also compared. The results show that the proposed control system is better for controlling uncertain and nonlinear processes.

  9. The effect of organic loading rate and retention time on hydrogen production from a methanogenic CSTR.

    Science.gov (United States)

    Pakarinen, O; Kaparaju, P; Rintala, J

    2011-10-01

    The possibility of shifting a methanogenic process for hydrogen production by changing the process parameters viz., organic loading rate (OLR) and hydraulic retention time (HRT) was evaluated. At first, two parallel semi-continuously fed continuously stirred tank reactors (CSTR) were operated as methanogenic reactors (M1 and M2) for 78 days. Results showed that a methane yield of 198-218 L/kg volatile solids fed (VS(fed)) was obtained when fed with grass silage at an OLR of 2 kgVS/m³/d and HRT of 30 days. After 78 days of operation, hydrogen production was induced in M2 by increasing the OLR from 2 to 10 kgVS/m³/d and shortening the HRT from 30 to 6 days. The highest H₂ yield of 42 L/kgVS(fed) was obtained with a maximum H₂ content of 24%. The present results thus demonstrate that methanogenic process can be shifted towards hydrogen production by increasing the OLR and decreasing HRT.

  10. Cassava Stillage Treatment by Thermophilic Anaerobic Continuously Stirred Tank Reactor (CSTR)

    Science.gov (United States)

    Luo, Gang; Xie, Li; Zou, Zhonghai; Zhou, Qi

    2010-11-01

    This paper assesses the performance of a thermophilic anaerobic Continuously Stirred Tank Reactor (CSTR) in the treatment of cassava stillage under various organic loading rates (OLRs) without suspended solids (SS) separation. The reactor was seeded with mesophilic anaerobic granular sludge, and the OLR increased by increments to 13.80 kg COD/m3/d (HRT 5d) over 80 days. Total COD removal efficiency remained stable at 90%, with biogas production at 18 L/d (60% methane). Increase in the OLR to 19.30 kg COD/m3/d (HRT 3d), however, led to a decrease in TCOD removal efficiency to 79% due to accumulation of suspended solids and incomplete degradation after shortened retention time. Reactor performance subsequently increased after OLR reduction. Alkalinity, VFA and pH levels were not significantly affected by OLR variation, indicating that no additional alkaline or pH adjustment is required. More than half of the SS in the cassava stillage could be digested in the process when HRT was 5 days, which demonstrated the suitability of anaerobic treatment of cassava stillage without SS separation.

  11. Enhanced anaerobic treatment of CSTR-digested effluent from chicken manure: The effect of ammonia inhibition.

    Science.gov (United States)

    Liu, Zhan-Guang; Zhou, Xue-Fei; Zhang, Ya-Lei; Zhu, Hong-Guang

    2012-01-01

    The effect of ammonia inhibition was evaluated during the enhanced anaerobic treatment of digested effluent from a 700m(3) chicken-manure continuous stirred tank reactor (CSTR). A 12.3L internal circulation (IC) reactor inoculated with an anaerobic granular sludge and operated at 35±1°C was employed for the investigation. With a corresponding organic loading rate of 1.5-3.5kg-COD/m(3)d over a hydraulic retention time of 1.5d, a maximum volumetric biogas production rate of 1.2m(3)/m(3)d and TCOD (total COD) removal efficiency ranging from 70% to 80% was achieved. However, the continual increase in the influent TAN content led to ammonia inhibition in the methanogenesis system. The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was presented to be the key controlling factor for the anaerobic treatment of semi-digested chicken manure, and further validation through shock loading and ammonia inhibition experiments was conducted. The threshold value of the SCOD/TAN ratio was determined to be 2.4 (corresponding to a TAN of 1250mg/L) at an influent pH of 8.5-9.

  12. Effect of Internal Flow Patterns on Heat transfer Performance of a Closed-end Oscillating Heat Pipe at Vertical Position

    Directory of Open Access Journals (Sweden)

    S. Rittidech

    2007-01-01

    Full Text Available This article describes the effects of varying bond numbers (Bo and aspect ratios (Le/d on flow pattern of a close-end oscillating heat-pipe (CEOHP. The CEOHPs used employed a glass tube with inside diameter of 3 mm. The length of evaporator of 100 and 150 mm (the lengths of evaporator adiabatic and condenser section were equal were employed with 10 turns. Observation of the flow pattern was conducted at 90° from the horizontal plane, with bond numbers of 1.8 and 2.6 with aspect ratios of 33.3 and 50. R141b and ethanol were used as the working fluids with filling ratio of 50% of internal volume of tube. The evaporator section was heated by heater and the condenser section was cooled by distilled water. The working temperature was controlled at 50°C. The temperature at adiabatic section and the inlet-outlet of distilled water at condenser section were recorded. The photographs of flow patterns at specific times were recorded at evaporator section by a digital camera and video camera were used to observe the flow patterns at evaporator section condenser together with adiabatic section and total part of CEOHP. It was found that the maximum heat flux occurred with Le/d 33 and Bo 2.6 an inside phenomena occurred is a dispersed bubble flow and slug flow.

  13. Impact of long-term drainage on summer groundwater flow patterns in the Mer Bleue peatland, Ontario, Canada

    Directory of Open Access Journals (Sweden)

    B. J. Kopp

    2013-09-01

    Full Text Available Long-term impacts of drier conditions on the hydrology of northern peatlands are poorly understood. We used long-term drainage near a historic drainage ditch, separating an area from the main peatland, as an analogue for long-term drying in a northern temperate bog. The objective was to identify the impact of drier conditions on ecohydrological processes and groundwater flow patterns in an area now forested and an area that maintained a bog-like character. Groundwater flow patterns alternated between mostly downward flow and occasionally upward flow in the bog area and were mostly upward-orientated in the forested area, which suggested that there the flow pattern had shifted from bog- to fen-like conditions. Flow patterns were in agreement with changes in post-drainage hydraulic conductivities, storage capacity of the peat and water table levels. Compared to the bog, hydraulic conductivities in the forested area were one to three orders of magnitude lower in the uppermost 0.75 m of peat (paired t test, p < 0.05. Bulk density had increased and the water table level was lower and more strongly fluctuating in the forested area. Our findings suggest hydraulic gradients and flow patterns have changed due to increased evapotranspiration and interception with the emergence of a tree cover. The smaller size of the now-forested area relative to the remaining bog area appeared to be important for the hydrological change. With the main Mer Bleue bog as hinterland, enhanced runoff to the drainage channel had little effect on hydrologic and vegetation patterns. In the cut-off, smaller, now forested area pervasive changes in vegetation and hydrologic processes occurred. The difference in response to local drainage raises questions about tipping points with respect to the impact of drying on peatland ecosystems that need to be addressed in future research.

  14. Interfacial wave patterns and their transitions in gas-liquid two-phase flow through horizontal ducts

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The interfacial wave patterns and their transition characteristics in gas-liquid two-phase flow through rectangular and circular horizontal conduits are investigated.The interfacial waves were traced and recorded by using conductance probes.With the experimental observation and the analysis,some kinds of different interfacial waves were distinguished and dfined,and then the interfacial wave patterns were given,which were compared with previous results.The interfacial wave transition mechanism between each interfacial wave pattern was discussed and a set of transition equations were presented to predict the interfacial wave pattern transitions.The repdictive results are in good agreement with the experimental data.

  15. Two-phase flow pattern measurements with a wire mesh sensor in a direct steam generating solar thermal collector

    Science.gov (United States)

    Berger, Michael; Mokhtar, Marwan; Zahler, Christian; Willert, Daniel; Neuhäuser, Anton; Schleicher, Eckhard

    2017-06-01

    At Industrial Solar's test facility in Freiburg (Germany), two phase flow patterns have been measured by using a wire mesh sensor from Helmholtz Zentrum Dresden-Rossendorf (HZDR). Main purpose of the measurements was to compare observed two-phase flow patterns with expected flow patterns from models. The two-phase flow pattern is important for the design of direct steam generating solar collectors. Vibrations should be avoided in the peripheral piping, and local dry-outs or large circumferential temperature gradients should be prevented in the absorber tubes. Therefore, the choice of design for operation conditions like mass flow and steam quality are an important step in the engineering process of such a project. Results of a measurement with the wire mesh sensor are the flow pattern and the plug or slug frequency at the given operating conditions. Under the assumption of the collector power, which can be assumed from previous measurements at the same collector and adaption with sun position and incidence angle modifier, also the slip can be evaluated for a wire mesh sensor measurement. Measurements have been performed at different mass flows and pressure levels. Transient behavior has been tested for flashing, change of mass flow, and sudden changes of irradiation (cloud simulation). This paper describes the measurements and the method of evaluation. Results are shown as extruded profiles in top view and in side view. Measurement and model are compared. The tests have been performed at low steam quality, because of the limits of the test facility. Conclusions and implications for possible future measurements at larger collectors are also presented in this paper.

  16. Revealing the Source of the Radial Flow Patterns in Proton-Proton Collisions using Hard Probes

    CERN Document Server

    Ortiz, Antonio; Bello, Héctor

    2016-01-01

    In this work, we propose a tool to reveal the origin of the collective-like phenomena observed in proton-proton collisions. We exploit the fundamental difference between the underlying mechanisms, color reconnection (CR) and hydrodynamics, which produce radial flow patterns in PYTHIA 8 and EPOS 3, respectively. Namely, the strength of the coupling between the soft and hard components which by construction is larger in PYTHIA 8 than in EPOS 3. We, therefore, study the transverse momentum ($p_{\\rm T}$) distributions of charged pions, kaons and (anti)protons as a function of the event multiplicity and the transverse momentum of the leading jet ($p_{\\rm T}^{\\rm jet}$), being all of them determined within a pseudorapidity interval of $|\\eta|<1$. Quantitative and qualitative differences between PYTHIA 8 and EPOS 3 are found in the $p_{\\rm T}$ spectra when (for a given multiplicity class) the leading jet $p_{\\rm T}$ is increased. In addition, we show that for low-multiplicity events jets can produce radial flow-l...

  17. Spatio-temporal cerebral blood flow perfusion patterns in cortical spreading depression

    Science.gov (United States)

    Verisokin, Andrey Yu.; Verveyko, Darya V.; Postnov, Dmitry E.

    2017-04-01

    Cortical spreading depression (CSD) is an example of one of the most common abnormalities in biophysical brain functioning. Despite the fact that there are many mathematical models describing the cortical spreading depression (CSD), most of them do not take into consideration the role of redistribution of cerebral blood flow (CBF), that results in the formation of spatio-temporal patterns. The paper presents a mathematical model, which successfully explains the CBD role in the CSD process. Numerical study of this model has revealed the formation of stationary dissipative structures, visually analogous to Turing structures. However, the mechanism of their formation is not diffusion. We show these structures occur due to another type of spatial coupling, that is related to tissue perfusion rate. The proposed model predicts that at similar state of neurons the distribution of blood flow and oxygenation may by different. Currently, this effect is not taken into account when the Blood oxygen-level dependent (BOLD) contrast imaging used in functional magnetic resonance imaging (fMRI). Thus, the diagnosis on the BOLD signal can be ambiguous. We believe that our results can be used in the future for a more correct interpretation of the data obtained with fMRI, NIRS and other similar methods for research of the brain activity.

  18. Reorganization of ice sheet flow patterns in Arctic Canada and the mid-Pleistocene transition

    Science.gov (United States)

    Refsnider, Kurt A.; Miller, Gifford H.

    2010-07-01

    Evidence for the evolution of Laurentide Ice Sheet (LIS) basal thermal regime patterns during successive glaciations is poorly preserved in the geologic record. Here we explore a new approach to constrain the distribution of cold-based ice across central Baffin Island in the eastern Canadian Arctic over many glacial-interglacial cycles by combining till geochemistry and cosmogenic radionuclide (CRN) data. Parts of the landscaped with geomorphic evidence for limited glacial erosion are covered by till characterized by high chemical index of alteration (CIA) values and CRN concentrations requiring complicated burial-exposure histories. Till from regions scoured by glacial erosion have CIA values indistinguishable from local bedrock and CRN concentrations that can be explained by simple exposure following deglaciation. CRN modeling results based on these constraints suggest that the weathered tills were deposited by 1.9 to 1.2 Ma, and by that time the fiorded Baffin Island coastline must have developed close to its modern configuration as piracy of ice flow by the most efficient fiord systems resulted in a major shift in the basal thermal regime across the northeastern LIS. The resultant concentration of ice flow in fewer outlet systems may help explain the cause of the mid-Pleistocene transition from 41- to 100-kyr glacial cycles.

  19. Revealing the source of the radial flow patterns in proton-proton collisions using hard probes

    Science.gov (United States)

    Ortiz, Antonio; Bencédi, Gyula; Bello, Héctor

    2017-06-01

    In this work, we propose a tool to reveal the origin of the collective-like phenomena observed in proton-proton collisions. We exploit the fundamental difference between the underlying mechanisms, color reconnection and hydrodynamics, which produce radial flow patterns in Pythia 8 and Epos 3, respectively. Specifically, we proceed by examining the strength of the coupling between the soft and hard components which, by construction, is larger in Pythia 8 than in Epos 3. We study the transverse momentum ({p}{{T}}) distributions of charged pions, kaons and (anti) protons in inelastic pp collisions at \\sqrt{s}=7 TeV produced at mid-rapidity. Specific selections are made on an event-by-event basis as a function of the charged particle multiplicity and the transverse momentum of the leading jet ({p}{{T}}{jet}) reconstructed using the FastJet algorithm at mid-pseudorapidity (| η | events the presence of jets can produce radial flow-like behavior. Motivated by our findings, we propose to perform a similar analysis using experimental data from RHIC and LHC.

  20. Traffic Management as a Service: The Traffic Flow Pattern Classification Problem

    Directory of Open Access Journals (Sweden)

    Carlos T. Calafate

    2015-01-01

    Full Text Available Intelligent Transportation System (ITS technologies can be implemented to reduce both fuel consumption and the associated emission of greenhouse gases. However, such systems require intelligent and effective route planning solutions to reduce travel time and promote stable traveling speeds. To achieve such goal these systems should account for both estimated and real-time traffic congestion states, but obtaining reliable traffic congestion estimations for all the streets/avenues in a city for the different times of the day, for every day in a year, is a complex task. Modeling such a tremendous amount of data can be time-consuming and, additionally, centralized computation of optimal routes based on such time-dependencies has very high data processing requirements. In this paper we approach this problem through a heuristic to considerably reduce the modeling effort while maintaining the benefits of time-dependent traffic congestion modeling. In particular, we propose grouping streets by taking into account real traces describing the daily traffic pattern. The effectiveness of this heuristic is assessed for the city of Valencia, Spain, and the results obtained show that it is possible to reduce the required number of daily traffic flow patterns by a factor of 4210 while maintaining the essence of time-dependent modeling requirements.

  1. Impact of long-term drainage on summer groundwater flow patterns in the Mer Bleue peatland, Ontario, Canada

    Directory of Open Access Journals (Sweden)

    B. J. Kopp

    2013-01-01

    Full Text Available Long-term impacts of a drier climate on coupled hydrology and carbon cycling in northern peatlands are poorly understood. We used a historic drainage ditch, separating an area from the main peatland, as an analogue for long-term drying in a northern temperate bog. The objective was to identify the impact of drier conditions on ecohydrological processes and groundwater flow patterns in an area now wooded and an area that maintained bog character. Groundwater flow patterns alternated between downward flow and upward flow in the bog area and were mostly upward orientated in the wooded area. Flow patterns were in agreement with changes in post-drainage hydraulic conductivities, storage capacity of the peat and hydraulic gradients. Compared to the bog, hydraulic conductivities in the wooded area were one to three orders of magnitude lower in the uppermost 0.75 m (paired t-test, p<0.05 of peat but partly higher below. Bulk density had increased and the water table level was lower and more strongly fluctuating. Our findings suggest hydraulic gradients and flow patterns have changed due to increased evapotranspiration and interception with the emergence of a tree cover. The smaller size of the now-forested area relative to the remaining bog area appeared to be important for the hydrological change. When water supply from undisturbed areas was large, enhanced runoff to the drainage channel had little effect on hydrologic patterns and vegetation pattern, whereas in the smaller, now forested area pervasive changes in vegetation and hydrologic processes occurred. This finding raises questions about tipping points with respect to the impact of drying on bog ecosystems that need to be addressed in future research.

  2. Convective thermal fluxes in unsteady non-homogeneous flows generating complex three dimensional vorticity patterns

    Science.gov (United States)

    Tellez Alvarez, Jackson David; Redondo, Jose Manuel; Sanchez, Jesu Mary

    2016-04-01

    The improvements in experimental methods and high resolution image analysis are nowadays able to detect subtle changes in the structure of the turbulence over a wide range of temporal and spatial scales [1], we compare the scaling shown by different mixing fronts driven by buoyancy that form convective driven mixing. We use PIV and density front tracking in several experimental configurations akin to geophysical overturning [2, 3]. We parametrize the role of unstable stratification by means of the Rayleigh and Atwood numbers and compare the scaling and the multifractal structure functions of the different markers used to visualize the non-homogeneous. Both reactive and passive scalar tracers are used to investigate the mixing structure and the intermittency of the flow. Different initial conditions are compared and the mixing efficiency of the overall turbulent process is evaluated [4 - 6]. Diffusion is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of Thermoelectric generated heating and cooling [2, 4]. Patterns arise by setting up a convective flow generated by a buoyant heat flux either in the base or in a side wall of the convective enclosure [1, 6]. The experiments described here investigate high Prandtl number mixing using brine or sugar solutions and fresh water in order to form a density interface and low Prandtl number mixing with only temperature gradients [7]. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [8, 9]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. The experiments described here investigate high Prandtl number mixing using salt or sugar solutions and

  3. Use of soil moisture dynamics and patterns at different spatio-temporal scales for the investigation of subsurface flow processes

    Directory of Open Access Journals (Sweden)

    T. Blume

    2009-07-01

    Full Text Available Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale and binary indicator maps (for the long-term and hillslope scale. Annual dynamics of soil moisture and decimeter-scale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a data-scarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to

  4. Understanding thermo-fluidic characteristics of a glass tube closed loop pulsating heat pipe: flow patterns and fluid oscillations

    Science.gov (United States)

    Karthikeyan, V. K.; Ramachandran, K.; Pillai, B. C.; Brusly Solomon, A.

    2015-12-01

    An experimental program has been carried out to understand the thermo-fluidic characterization of deionized (DI) water charged closed loop pulsating heat pipe (CLPHP) with flow patterns and fluid oscillations. The CLPHP is examined under vertical and horizontal heating modes with varying heat power. The flow patterns along with fluid oscillations are correlated with thermal performance of the CLPHP. Further, the CLPHP with copper oxide nanofluid study is carried out to understand operational behavior of the device. Fast Fourier frequencies, average frequency of the internal fluid temperature are investigated. Several important features of CLPHP operation are identified by the visual study.

  5. Evaluation of Blood Flow Patterns of Solitary Pulmonary Nodules with Dynamic Multi-slice Spiral Computed Tomography

    Institute of Scientific and Technical Information of China (English)

    LIShenjiang; XIAOXiangsheng; LIHuimin; LIUShiyuan; LIChengzhou; ZHANGChenshi; TAOZhiwei; YANGChunshan

    2004-01-01

    To evaluate the efficacy of dynamic multi-slice spiral computed tomography (MSCT) for providing quantitative information about blood flow patterns of solitary pulmonary nodules (SPNs) and differentiating solitary pulmonary nodules (SPNs). Methods: 37 patients with SPNs (diameter0.01). SFN-to-aorta ratio in inflammatory SPNs (20.78%±4.14) was significantly higher than that in benign (2.00%±2.26) and malig nant (14.63%±6.22) SPNs (P0.01). Conclusion: MSCT provides quantitative information about blood flow patterns of solitary pulmonary nodules (SPNs) and is applicable diagnostic method for differentiating SPNs.

  6. Effect of organic loading on CSTR-UASB two-phase anaerobic system%有机负荷对CSTR-UASB两相厌氧系统的影响

    Institute of Scientific and Technical Information of China (English)

    赵健慧; 王玥; 李永峰

    2014-01-01

    采用连续流CSTR-UASB两相厌氧反应装置,CSTR以人工配制的红糖水作为发酵底物,其液相末端产物作为UASB的反应底物,污水处理厂剩余污泥作为反应器的启动污泥,反应器实现稳定运行(CSTR为乙醇型发酵)后,在其它参数不变的情况下,通过改变有机负荷,研究其对CSTR-UASB两相厌氧系统的影响.有机负荷从12 kg/(m3·d)提升至32 kg/(m3·d)的过程分为六个阶段,结果表明厌氧活性污泥产氢能力持续升高,在有机负荷为32 kg/(m3·d)时,最大产氢量为12.8L/d,较初始有机负荷12 kg/(m3·d)时提高了71.9%;产甲烷量随有机负荷的升高先增大后减小,在有机负荷为24 kg/(m3·d)时,最大产甲烷量为18.5L/d;当有机负荷提高至28 kg/(m3·d)时,总COD去除率达最大值72%.因此,CSTR-UASB两相厌氧系统对红糖废水具有较好的降解效果,同时能源回收效率较高.

  7. The effects of channel diameter on flow pattern, void fraction and pressure drop of two-phase air-water flow in circular micro-channels

    Energy Technology Data Exchange (ETDEWEB)

    Saisorn, Sira [Energy Division, The Joint Graduate School of Energy and Environment (JGSEE), King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand); Wongwises, Somchai [Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Lab. (FUTURE), Department of Mechanical Engineering, King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)

    2010-05-15

    Two-phase air-water flow characteristics are experimentally investigated in horizontal circular micro-channels. Test sections are made of fused silica. The experiments are conducted based on three different inner diameters of 0.53, 0.22 and 0.15 mm with the corresponding lengths of 320, 120 and 104 mm, respectively. The test runs are done at superficial velocities of gas and liquid ranging between 0.37-42.36 and 0.005-3.04 m/s, respectively. The flow visualisation is facilitated by systems mainly including stereozoom microscope and high-speed camera. The flow regime maps developed from the observed flow patterns are presented. The void fractions are determined based on image analysis. New correlation for two-phase frictional multiplier is also proposed for practical applications. (author)

  8. Groundwater occurrence and flow patterns in the Ishiagu mining area of southeastern Nigeria

    Institute of Scientific and Technical Information of China (English)

    I.C.EZEKWE; E.ODUBO; G.N.CHIMA; I.S.ONWUCHEKWA

    2012-01-01

    The Ishiagu area is a water scarce region and has played host to mining activities for more than four decades.Mining-related activities have become a threat to potable water supply in the area.This paper is an attempt to show the extent of this threat and in particular,investigate the regional groundwater occurrence and flow pattern based on GPS,water well and geological data.This basinwide model can be used for further groundwater assessment,pollution control and contaminant management.Groundwater occurs between 2.4 and 9 m in the Lekwesi-Lokpaukwu area; 1.5-3.7 m in the Ndi-Ugbugbor-Ayaragu axis and 1.2-4.6 m in the Ishiagu area.Recharge areas include the Leru-Amaubiri-Lekwesi sandstone hills and the lhetutu-Ugwuajirija mine field.While the ultimate sink of contamiants is the Ivo River system,other discharge axis is the Ishiagu-Ayaragu axis and the Ogwor Ndi-Ugbugbor zone.An unconfined and a confined (> 10)circulation groundwater system was inferred,and flow model reveals that a large part of Ishiag-Ayaragu and NdiUgbugbor part of the study area suffer polluted recharge from the Pb/Zn mining area.Groundwater was also subjected to hierarchical cluster analysis and the existence of 3-4 hydrological regimes,which revealed:Unpolluted recharge areas,areas affected by polluted recharge,a deep water and shallow water circulation and mine effluents.

  9. From time-series to complex networks: Application to the cerebrovascular flow patterns in atrial fibrillation

    Science.gov (United States)

    Scarsoglio, Stefania; Cazzato, Fabio; Ridolfi, Luca

    2017-09-01

    A network-based approach is presented to investigate the cerebrovascular flow patterns during atrial fibrillation (AF) with respect to normal sinus rhythm (NSR). AF, the most common cardiac arrhythmia with faster and irregular beating, has been recently and independently associated with the increased risk of dementia. However, the underlying hemodynamic mechanisms relating the two pathologies remain mainly undetermined so far; thus, the contribution of modeling and refined statistical tools is valuable. Pressure and flow rate temporal series in NSR and AF are here evaluated along representative cerebral sites (from carotid arteries to capillary brain circulation), exploiting reliable artificially built signals recently obtained from an in silico approach. The complex network analysis evidences, in a synthetic and original way, a dramatic signal variation towards the distal/capillary cerebral regions during AF, which has no counterpart in NSR conditions. At the large artery level, networks obtained from both AF and NSR hemodynamic signals exhibit elongated and chained features, which are typical of pseudo-periodic series. These aspects are almost completely lost towards the microcirculation during AF, where the networks are topologically more circular and present random-like characteristics. As a consequence, all the physiological phenomena at the microcerebral level ruled by periodicity—such as regular perfusion, mean pressure per beat, and average nutrient supply at the cellular level—can be strongly compromised, since the AF hemodynamic signals assume irregular behaviour and random-like features. Through a powerful approach which is complementary to the classical statistical tools, the present findings further strengthen the potential link between AF hemodynamic and cognitive decline.

  10. Interpreting the spatio-temporal patterns of sea turtle strandings: Going with the flow

    Science.gov (United States)

    Hart, K.M.; Mooreside, P.; Crowder, L.B.

    2006-01-01

    Knowledge of the spatial and temporal distribution of specific mortality sources is crucial for management of species that are vulnerable to human interactions. Beachcast carcasses represent an unknown fraction of at-sea mortalities. While a variety of physical (e.g., water temperature) and biological (e.g., decomposition) factors as well as the distribution of animals and their mortality sources likely affect the probability of carcass stranding, physical oceanography plays a major role in where and when carcasses strand. Here, we evaluate the influence of nearshore physical oceanographic and wind regimes on sea turtle strandings to decipher seasonal trends and make qualitative predictions about stranding patterns along oceanfront beaches. We use results from oceanic drift-bottle experiments to check our predictions and provide an upper limit on stranding proportions. We compare predicted current regimes from a 3D physical oceanographic model to spatial and temporal locations of both sea turtle carcass strandings and drift bottle landfalls. Drift bottle return rates suggest an upper limit for the proportion of sea turtle carcasses that strand (about 20%). In the South Atlantic Bight, seasonal development of along-shelf flow coincides with increased numbers of strandings of both turtles and drift bottles in late spring and early summer. The model also predicts net offshore flow of surface waters during winter - the season with the fewest relative strandings. The drift bottle data provide a reasonable upper bound on how likely carcasses are to reach land from points offshore and bound the general timeframe for stranding post-mortem (strandings follow a seasonal regime predictable from physical oceanography and mimicked by drift bottle experiments. Managers can use these findings to reevaluate incidental strandings limits and fishery takes for both nearshore and offshore mortality sources. ?? 2005 Elsevier Ltd. All rights reserved.

  11. Towards the On-line Identification of Peer-to-peer Flow Patterns

    Directory of Open Access Journals (Sweden)

    Antonio Nogueira

    2009-04-01

    Full Text Available The number and variety of IP applications have hugely increased in the last few years. Among them, peer-to-peer (P2P file-sharing applications have become very popular: more users are continuously joining such systems and more objects are being made available, seducing even more users to join. An accurate mapping of traffic to applications is important for a wide range of network management tasks. Besides, traditional mapping approaches have become increasingly inaccurate because many applications use non-default or ephemeral port numbers, use well-known port numbers associated with other applications, change application signatures or use traffic encryption. This paper proposes a framework to identify Internet applications that can be mainly used in situations where existing identification frameworks are not efficient or can not be used at all. The core block of the identification tool is based on neural networks and is able to identify different flow patterns generated by various Internet applications. Neural network based identification relies on a previous identification of the different IP applications that can be obtained offline using any reliable method. In this way, the paper also presents a module to process IP traffic flows and identify the underlying applications using payload analysis techniques. The identification results obtained from this tool are used in the training phase of the neural network identification framework. The accuracy of the identification framework was evaluated by performing a set of intensive tests and the results obtained show that, when conveniently trained, neural networks constitute a valuable tool to identify Internet applications while being, at the same time, immune to the most important disadvantages presented by other identification methods.

  12. Experimental study on two-phase gas-liquid flow patterns at normal and reduced gravity conditions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Experimental studies have been performed for horizontal two-phase air-water flows at nor-mal and reduced gravity conditions in a square cross-section channel. The experiments at reducedgravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namelybubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gassuperficial velocities at both conditions. Semi-theoretical Weber number model is developed to includethe shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agree-ment with the experimental slug-annular transition under both conditions. For the case of two-phasegas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observedboundary between bubble and slug flows.

  13. Optimal forcing perturbations for regional flow patterns conditioning polar low development

    Science.gov (United States)

    Kristiansen, Jørn; Iversen, Trond; Jung, Thomas; Barkmeijer, Jan

    2013-04-01

    olar lows are short lived maritime mesoscale cyclones that develop because of processes unique to the Polar Regions. In the ice-free Nordic and Barents Seas they are associated with violent weather during wintertime and form in cold air outbreaks underneath a cold through. The longer predictability of the large-scales may provide early warnings of the potential for polar lows. We investigate the rare events when the atmosphere is highly sensitive to small external forcings that excite changes in the variability of the North Atlantic Oscillation (NAO). Employing a numerical weather prediction model, the period 1957-2002 is sampled for 4-day optimal forcing sensitivity patterns (FSPs). The highly sensitive events are relatively well-defined. A flow pattern resembling the negative-phase NAO is identified as a potential precursor of the most unpredictable transitions in the NAO. The least sensitive events are dominated by a coinciding cyclonic circulation. In the former there is high polar low potential (40-45%) in the northern North Atlantic but it is low south of Iceland. The least sensitive events display high potential along the storm track reaching 80% south of Iceland. The FSPs tend to either strengthen or hamper the transition toward the negative-phase NAO. The strengthened circulation makes the atmosphere favourable in 70% of the events for the formation of polar lows in the Nordic and Barents Seas with high potentials also in the North Sea. From the hampered transition we learn that in the Nordic Seas high- and low-pressure systems can produce similar levels of polar low potential. Temperature and momentum are equally important forcing variables and there are positive feedbacks between them. The forcing is dominantly in-situ and strongest in mid-troposphere. The variability is more localized and larger than the average. Close to the surface the FSPs appear influenced by the Norwegian current.

  14. Disturbed flow in a patient-specific arteriovenous fistula for hemodialysis: Multidirectional and reciprocating near-wall flow patterns.

    Science.gov (United States)

    Ene-Iordache, Bogdan; Semperboni, Cristina; Dubini, Gabriele; Remuzzi, Andrea

    2015-07-16

    Actual surgical creation of vascular access has unacceptable failure rates of which stenosis formation is a major cause. We have shown previously in idealized models of side-to-end arteriovenous fistula that disturbed flow, a near-wall hemodynamic condition characterized by low and oscillating fluid shear stress, develops in focal points that corresponds closely to the sites of future stenosis. Our present study was aimed at investigating whether disturbed flow occurs in patient-specific fistulae, too. We performed an image-based computational fluid dynamics study within a realistic model of wrist side-to-end anastomosis fistula at six weeks post-surgery, with subject-specific blood rheology and boundary conditions. We then categorized disturbed flow by means of established hemodynamic wall parameters. The numerical analysis revealed laminar flow within the arterial limbs and a complex flow field in the swing segment, featuring turbulent eddies leading to high frequency oscillation of the wall shear stress vectors. Multidirectional disturbed flow developed on the anastomosis floor and on the whole swing segment. Reciprocating disturbed flow zones were found on the distal artery near the floor and on the inner wall of the swing segment. We have found that both multidirectional and reciprocating disturbed flow develop on the inner side of the swing segment in a patient-specific side-to-end fistula used for vascular access after six weeks post-operatively. This has obvious implications for elucidating the hemodynamic forces involved in the initiation of venous wall thickening in vascular access. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Source Water Flow Pathways In Forested, Mountain, Headwater Streams: A Link Between Sediment Movement Patterns And Stream Water Chemistry.

    Science.gov (United States)

    Martin, S.; Conklin, M. H.; Liu, F.

    2015-12-01

    Three years of continuous and discrete sediment and water quality data, from four forested, mountain, headwater catchments in the Sierra Nevada, is used to identify water sources, determine the importance of sub-surface flow pathways, detect any changes in source waters due to seasonal variation or drought, and link flow pathways with observed patterns of in-channel sediment movement within the study watersheds. Patterns in stream chemistry and turbidity point to infiltration as the dominant flow pathway within these catchments. Data support a flow pathway conceptual model in which precipitation water infiltrates into the shallow or deeper subsurface, increasing the hydraulic head of the water table and pushing pre-event water into the stream ahead of event water. Study catchments contain perennial streams and are characterized by a Mediterranean climate with a distinct wet and dry season. Sites are located in the rain-snow transition zone with snow making up 40 to 60 percent of average annual precipitation. Barring human disturbances such as logging/grazing (compaction) or fire (hydrophobicity), catchment soils have high infiltration capacities. Springs and seeps maintain baseflow during the summer low-flow season, and shifting chemical signals within the streams indicate the increased importance of sub-surface water sources during drought years. End-member mixing analysis was conducted to identify possible water end members. Turbidity hysteresis patterns described by previous studies show in-channel sources are dominant for discharge events year round, and there is no difference in fine sediment delivery to streams with or without a soil protecting layer of snow on the land surface. The dominance of sub-surface water sources and evidence for infiltration flow fits with turbidity data, as little material is reaching the stream due to erosive overland flow. An understanding of flow pathways provides a foundation for sustainable land use management in forested

  16. Simulation of Few Bifurcation Phase Diagrams of Belousov-Zhabotinsky Reaction with Eleven Variable Chaotic Model in CSTR

    Directory of Open Access Journals (Sweden)

    B. Swathi

    2009-01-01

    Full Text Available Simulation of the Gyorgyi, Rempe and Field eleven variable chaotic model in CSTR [Continuously Stirred Tank Reactor] is performed with respect to the concentrations of malonic acid and [Ce(III]. These simulation studies show steady state, periodic and non-periodic regions. These studies have been presented as two variable bifurcation phase diagrams. We also have observed the bursting phenomenon under different set of constraints. We have given much importance on computer simulation work but not included the experimental methods in this paper.

  17. A combination anaerobic digestion scheme for biogas production from dairy effluent-CSTR and ABR, and biogas upgrading

    DEFF Research Database (Denmark)

    Jürgensen, Lars; Ehimen, Ehiaze Augustine; Born, Jens

    2017-01-01

    substrate organic loading rates between 1.25 and 4.50 kg m-3 d-1. The average chemical oxygen demand (COD) removal was 82% with a biogas yield of 0.26 m3 kg-1. The use of the derived biogas for the Sabatier process to convert hydrogen into CH4 showed no disadvantages compared to synthetic gas mixtures....... The combination of CSTR and ABR overcame the individual disadvantages of both reactor types. The investigated anaerobic digestion system can be further optimized and adopted to replace conventional waste water treatment systems....

  18. 卡尔曼滤波在CSTR系统中的应用%Application of Kalman filter in CSTR system

    Institute of Scientific and Technical Information of China (English)

    高兴泉; 高玉坤; 姜德龙

    2003-01-01

    从现在的工艺条件及经济方面考虑,在连续搅拌反应釜(CSTR)系统中直接测量其组分的浓度是很困难的.本文基于卡尔曼滤波技术,通过实时测量反应釜的反应温度与冷却温度来在线估计其组分的浓度,取得了很好的效果.最后给出了在CSTR系统中应用的仿真结果.

  19. Interfacial-tension-force model for the wavy stratified liquid-liquid flow pattern transition: The usage of two different approaches

    Science.gov (United States)

    de Castro, Marcelo Souza; Rodriguez, Oscar Mauricio Hernandez

    2016-06-01

    The study of the hydrodynamic stability of flow patterns is important in the design of equipment and pipelines for multiphase flows. The maintenance of a particular flow pattern becomes important in many applications, e.g., stratified flow pattern in heavy oil production avoiding the formation of emulsions because of the separation of phases and annular flow pattern in heat exchangers which increases the heat transfer coefficient. Flow maps are drawn to orientate engineers which flow pattern is present in a pipeline, for example. The ways how these flow maps are drawn have changed from totally experimental work, to phenomenological models, and then to stability analysis theories. In this work an experimental liquid-liquid flow map, with water and viscous oil as work fluids, drawn via subjective approach with high speed camera was used to compare to approaches of the same theory: the interfacial-tension-force model. This theory was used to drawn the wavy stratified flow pattern transition boundary. This paper presents a comparison between the two approaches of the interfacial-tension-force model for transition boundaries of liquid-liquid flow patterns: (i) solving the wave equation for the wave speed and using average values for wave number and wave speed; and (ii) solving the same equation for the wave number and then using a correlation for the wave speed. The results show that the second approach presents better results.

  20. Effect of force fields on pool boiling flow patterns in normal and reduced gravity

    Science.gov (United States)

    di Marco, P.; Grassi, W.

    2009-05-01

    This paper reports the observations of boiling flow patterns in FC-72, performed during a microgravity experiment, recently flown aboard of Foton-M2 satellite, in some instances with the additional aid of an electrostatic field to replace the buoyancy force. The heater consisted of a flat plate, 20 × 20 mm2, directly heated by direct current. Several levels of liquid subcooling (from 20 to 6 K) and heat fluxes up to 200 kW/m2 were tested. A complete counterpart test, carried out on ground before the mission, allowed direct comparison with terrestrial data. The void fraction in microgravity revealed much larger than in normal gravity condition: this may be attributed to increased bubble coalescence that hinders vapor condensation in the bulk of the subcooled fluid. In several cases, an oscillatory boiling behavior was detected, leading to periodical variation of average wall overheating of some degrees. The electric field confirmed to be very effective, even at low values of applied voltage, in reducing bubble size, thus improving their condensation rate in the bulk fluid, and in enhancing heat transfer performance, suppressing the boiling oscillations and preventing surface dryout.

  1. Study of air-liquid flow patterns in hydrocyclone enhanced by air bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Z.; Wang, H.; Tu, S.T. [School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai (China)

    2009-01-15

    In order to improve the oil-water separation efficiency of a hydrocyclone, a new process utilizing air bubbles has been developed to enhance separation performance. Using the two-component phase Doppler particle analyzer (PDPA) technique, the velocities of two phases, air and liquid, and air bubble diameter were measured in a hydrocyclone. The air-liquid mixing pump can produce 15 to 60 {mu}m-diameter air bubbles in water. There is an optimum air-liquid ratio for oil-water separation of a hydrocyclone enhanced by air bubbles. An air core occurs in the hydrocyclone when the air-liquid ratio is more than 1 %. The velocities of air bubbles have a similar flow pattern to the water phase. The axial and tangential velocity differences of the air bubbles at different air-liquid ratio are greater near the wall and near the core of the hydrocyclone. The measured results show that the size distribution of the air bubbles produced by the air-liquid mixing pump is beneficial to the process where air bubbles capture oil droplets in the hydrocyclone. These studies are helpful to understand the separation mechanism of a hydrocyclone enhanced by air bubbles. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  2. Pressure distributions and oil-flow patterns for a swept circulation-control wing

    Science.gov (United States)

    Keener, Earl R.; Sanderfer, Dwight T.; Wood, Norman J.

    1987-01-01

    Pressure distributions and photographs of oil flow patterns are presented for a circulation control wing. The model was an aspect ratio four semispan wing mounted on the side wall of the NASA Ames Transonic Wind Tunnel. The airfoil was a 20 percent thick ellipse, modified with circular leading and trailing edges of 4 percent radius, and had a 25.4 cm constant chord. This configuration does not represent a specific wing design, but is generic. A full span, tangetial, rearward blowing, circulation control slot was incorporated ahead of the trailing edge on the upper surface. The wing was tested at Mach numbers from 0.3 to 0.75 at sweep angle of 0 to 45 deg with internal to external pressure ratios of 1.0 to 3.0. Lift and pitching momemt coefficients were obtained from measured pressure distributions at five span stations. When the conventional corrections resulting from sweep angle are applied to the lift and moment of circulation control sections, no additional corrections are necessary to account for changes in blowing efficiency. This is demonstrated for an aft sweep angle of 45 deg. An empirical technique for estimating the downwash distribution of a swept wing was validated.

  3. Membrane fouling and dialysate flow pattern in an internal filtration-enhancing dialyzer.

    Science.gov (United States)

    Yamamoto, Ken-ichiro; Hiwatari, Michihito; Kohori, Fukashi; Sakai, Kiyotaka; Fukuda, Makoto; Hiyoshi, Tatsuo

    2005-01-01

    For efficient removal of large molecular weight solutes by dialysis, several types of internal filtration-enhancing dialyzers (IFEDs) are commercially available. However, in a pressure-driven membrane separation process (i.e., filtration), membrane fouling caused by adhesion of plasma proteins is a severe problem. The objective of the present study is to investigate the effects of internal filtration on membrane fouling based on the membrane's pure-water permeability, diffusive permeability, and sieving coefficient. Hemodialysis experiments were performed with two different dialyzers, IFEDs and non-IFEDs. Local membrane fouling in each dialyzer was evaluated by measuring the pure-water permeability, the diffusive permeability, and the sieving coefficient of native membranes and membranes treated with bovine blood. The effects of packing ratio on dialysate flow pattern were also evaluated by measuring the time required for an ion tracer to reach electrodes placed in the dialyzers. In the IFED, membrane fouling caused by protein adhesion is increased because of enhanced internal filtration only at the early stage of dialysis, and this fouling tends to occur only near the dialysate outlet port. However, enhanced internal filtration has little effect on measured membrane transfer parameters.

  4. Characteristics of two-phase flow pattern transitions and pressure drop of five refrigerants in horizontal circular small tubes

    Energy Technology Data Exchange (ETDEWEB)

    Pamitran, A.S. [Department of Mechanical Engineering, University of Indonesia, Kampus Baru UI, Depok 16424 (Indonesia); Choi, Kwang-Il [Graduate School, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550-749 (Korea); Oh, Jong-Taek [Department of Refrigeration and Air Conditioning Engineering, Chonnam National University, San 96-1, Dunduk-Dong, Yeosu, Chonnam 550-749 (Korea); Hrnjak, Pega [Department of Mechanical Science and Engineering, ACRC, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801 (United States)

    2010-05-15

    An experimental investigation on the characteristics of two-phase flow pattern transitions and pressure drop of R-22, R-134a, R-410A, R-290 and R-744 in horizontal small stainless steel tubes of 0.5, 1.5 and 3.0 mm inner diameters is presented. Experimental data were obtained over a heat flux range of 5-40 kW/m{sup 2}, mass flux range of 50-600 kg/(m{sup 2} s), saturation temperature range of 0-15 C, and quality up to 1.0. Experimental data were evaluated with Wang et al. and Wojtan et al. [Wang, C.C., Chiang, C.S., Lu, D.C., 1997. Visual observation of two-phase flow pattern of R-22, R-134a, and R-407C in a 6.5-mm smooth tube. Exp. Therm. Fluid Sci. 15, 395-405; Wojtan, L., Ursenbacher, T., Thome, J.R., 2005. Investigation of flow boiling in horizontal tubes: part I - a new diabatic two-phase flow pattern map. Int. J. Heat Mass Transfer 48, 2955-2969.] flow pattern maps. The effects of mass flux, heat flux, saturation temperature and inner tube diameter on the pressure drop of the working refrigerants are reported. The experimental pressure drop was compared with the predictions from some existing correlations. A new two-phase pressure drop model that is based on a superposition model for two-phase flow boiling of refrigerants in small tubes is presented. (author)

  5. Flow patterns and boundary conditions for inlet and outlet conduits of large pump system with low head

    Institute of Scientific and Technical Information of China (English)

    徐磊; 陆伟刚; 陆林广; 董雷; 王兆飞

    2014-01-01

    The flow patterns in the inlet and outlet conduits have a decisive effect on the safe, stable, and highly efficient operation of the pump in a large pumping station with low head. The numerical simulation of three-dimensional (3D) turbulence flow in conduits is an important method to study the hydraulic performance and conduct an optimum hydraulic design for the conduits. With the analyses of the flow patterns in the inlet and outlet conduits, the boundary conditions of the numerical simulation for them can be determined. The main obtained conclusions are as follows: (i) Under normal operation conditions, there is essentially no pre-swirl flow at the impeller chamber inlet of an axial-flow pump system, based on which the boundary condition at the inlet conduit may be defined. (ii) The circulation at the guide vane outlet of an axial-flow pump system has a great effect on the hydraulic performance of the outlet conduit, and there is optimum circulation for the performance. Therefore, it is strongly suggested to design the guide vane according to the optimum circulation. (iii) The residual circulation at the guide vane outlet needs to be considered for the inlet boundary condition of the outlet conduit, and the value of the circulation may be measured in a specially designed test model.

  6. Effects of lung disease on the three-dimensional structure and air flow pattern in the human airway tree

    Science.gov (United States)

    van de Moortele, Tristan; Nemes, Andras; Wendt, Christine; Coletti, Filippo

    2016-11-01

    The morphological features of the airway tree directly affect the air flow features during breathing, which determines the gas exchange and inhaled particle transport. Lung disease, Chronic Obstructive Pulmonary Disease (COPD) in this study, affects the structural features of the lungs, which in turn negatively affects the air flow through the airways. Here bronchial tree air volume geometries are segmented from Computed Tomography (CT) scans of healthy and diseased subjects. Geometrical analysis of the airway centerlines and corresponding cross-sectional areas provide insight into the specific effects of COPD on the airway structure. These geometries are also used to 3D print anatomically accurate, patient specific flow models. Three-component, three-dimensional velocity fields within these models are acquired using Magnetic Resonance Imaging (MRI). The three-dimensional flow fields provide insight into the change in flow patterns and features. Additionally, particle trajectories are determined using the velocity fields, to identify the fate of therapeutic and harmful inhaled aerosols. Correlation between disease-specific and patient-specific anatomical features with dysfunctional airflow patterns can be achieved by combining geometrical and flow analysis.

  7. The effect of flow pattern around a bubble rising near a vertical wall, on the wall to liquid heat transfer

    Science.gov (United States)

    Bhuvankar, Pramod; Dabiri, Sadegh

    2016-11-01

    Two-phase flow is an effective means for heat removal due to the enhanced convective effect caused by bubbly flow and the usually high latent heat of vaporization of the liquid phase. We present a numerical study of the effect of flow patterns around a single bubble rising in shear flow near a vertical wall, on the wall-to-liquid heat transfer. The Navier-Stokes equations are solved in a frame of reference moving with the bubble, by using the front tracking method for interface tracking. Our simulations reveal an enhancement of heat transfer downstream of the bubble, and a less pronounced diminishment of heat transfer upstream of the bubble. We observe that in the range of 5 Archimedes number. The heat transfer enhancement is attributed to flow reversal happening in a confined region of the shear flow, in the presence of a bubble. The analytical solution of 2 - D inviscid shear flow over a cylinder near a wall is used to identify two parameters of flow reversal namely 'reversal height' and 'reversal width'. These parameters are then used to qualitatively explain what we observe in 3 - D simulations.

  8. Augmented Lagrangian and penalty methods for the simulation of two-phase flows interacting with moving solids. Application to hydroplaning flows interacting with real tire tread patterns

    Science.gov (United States)

    Vincent, Stéphane; Sarthou, Arthur; Caltagirone, Jean-Paul; Sonilhac, Fabien; Février, Pierre; Mignot, Christian; Pianet, Grégoire

    2011-02-01

    The numerical simulation of the interaction between a free surface flow and a moving obstacle is considered for the analysis of hydroplaning flows. A new augmented Lagrangian method, coupled to fictitious domains and penalty methods, is proposed for the simulation of multi-phase flows. The augmented Lagrangian parameter is estimated by an automatic analysis of the discretization matrix resulting from the approximation of the momentum equations. The algebraic automatic augmented Lagrangian 3AL approach is validated on the natural convection in a differentially heated cavity, a two-dimensional collapse of a water column, the three-dimensional settling of a particle in a tank and the falling of a dense cylinder in air. Finally, the 3AL method is utilized to simulate the hydroplaning of a tire under various pattern shape conditions.

  9. Pattern Selection, Wave Formation, Turbulence and Vortex Breakdown in Spiral Flows

    Science.gov (United States)

    1990-01-01

    problems in rotating plane Couette - Poiseuille flow " (joint work with George H. Knightly), Contemporary Math., 108 (1990), to appear. The following...continuum of periodic waves in rotating plane Couette flow , and an analytic description of a mechanism to generate the turbulent-like flows observed in...during the period of the report: (1) "Waves in rotating plane Couette flow " (joint work with George H. Knightly, University of Massachusetts), Geometry

  10. Modeling of debris flow depositional patterns according to the catchment and sediment source area characteristics

    OpenAIRE

    2015-01-01

    A method to predict the most probable flow rheology in Alpine debris flows is presented. The methods classifies outcropping rock masses in catchments on the basis of the type of resulting unconsolidated deposits. The grain size distribution of the debris material and the depositional style of past debris flow events are related to the dominant flow processes: viscoplastic and frictional/collisional. Three catchments in the upper Susa Valley (Western Alps), characterized by different lithologi...

  11. Stripped elliptical galaxies as probes of ICM physics: I. Tails, wakes, and flow patterns in and around stripped ellipticals

    CERN Document Server

    Roediger, E; Nulsen, P E J; Forman, W R; Machacek, M; Randall, S; Jones, C; Churazov, E; Kokotanekova, R

    2014-01-01

    (abridged) Elliptical cluster galaxies are successively stripped of their gaseous atmospheres due to their motion through the ICM. The stripped galactic gas forms a 'tail' in the galaxy's wake. Deep X-ray observations reveal the fine-structure of the gas tail and of the interface between galactic gas and ICM. This fine-structure depends on dynamic conditions (galaxy potential, initial gas contents, orbit in the host cluster), stripping stage (early infall, pre-/post-pericenter passage), and on the still ill-constrained ICM plasma properties (thermal conductivity, viscosity, magnetic field structure). In a series of papers, we aim at disentangling dynamic and plasma effects in order to use observed stripped ellipticals as probes of the ICM plasma properties. This first paper determines flow phases and flow patterns of successive gas stripping by means of hydrodynamical simulations. During quasi-steady stripping, the flow of ICM around the remnant atmosphere is similar to the flow around solid bodies, including...

  12. Physics and (patho)physiology in confined flows: from colloidal patterns to cytoplasmic rheology and sickle cell anemia

    Science.gov (United States)

    Mahadevan, L.

    2015-03-01

    I will discuss a few problems that involve the interaction of fluids and solids in confined spaces. (i) Jamming in pressure-driven suspension flows that show a transition from Stokes flows to Darcy flows as the solids start to lock, as in evaporative patterning in colloids (e.g. coffee stain formation) .(ii) Jamming and clogging of red blood cells, as in sickle-cell pathophysiology, with implications for other diseases that involve jamming. (iii) The mechanical response of crowded networks of filaments bathed in a fluid, as in the cytoskeleton, that can be described by poroelasticity theory. In each case, I will show how simple theories of multiphase flow and deformation can be used to explain a range of experimental observations, while failing to account for others, along with some thoughts on how to improve them.

  13. Design configurations affecting flow pattern and solids accumulation in horizontal free water and subsurface flow constructed wetlands.

    Science.gov (United States)

    Pedescoll, A; Sidrach-Cardona, R; Sánchez, J C; Carretero, J; Garfi, M; Bécares, E

    2013-03-01

    The aim of this study was to evaluate the effect of different horizontal constructed wetland (CW) design parameters on solids distribution, loss of hydraulic conductivity over time and hydraulic behaviour, in order to assess clogging processes in wetlands. For this purpose, an experimental plant with eight CWs was built at mesocosm scale. Each CW presented a different design characteristic, and the most common CW configurations were all represented: free water surface flow (FWS) with different effluent pipe locations, FWS with floating macrophytes and subsurface flow (SSF), and the presence of plants and specific species (Typha angustifolia and Phragmites australis) was also considered. The loss of the hydraulic conductivity of gravel was greatly influenced by the presence of plants and organic load (representing a loss of 20% and c.a. 10% in planted wetlands and an overloaded system, respectively). Cattail seems to have a greater effect on the development of clogging since its below-ground biomass weighed twice as much as that of common reed. Hydraulic behaviour was greatly influenced by the presence of a gravel matrix and the outlet pipe position. In strict SSF CW, the water was forced to cross the gravel and tended to flow diagonally from the top inlet to the bottom outlet (where the inlet and outlet pipes were located). However, when FWS was considered, water preferentially flowed above the gravel, thus losing half the effective volume of the system. Only the presence of plants seemed to help the water flow partially within the gravel matrix. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Rainfall-triggering response patterns of post-seismic debris flows in the Wenchuan earthquake area

    NARCIS (Netherlands)

    Zhou, W.; Tang, C.; van Asch, Th.W.J.; Zhou, nn.

    2013-01-01

    Several giant debris flows occurred in southwestern China after the Wenchuan earthquake, causing serious casualties and economic losses. Debris flows were frequently triggered after the earthquake. A relatively accurate prediction of these post-seismic debris flows can help to reduce the consequent

  15. THE PATTERN OF AIR FLOW OUT OF THE MOUTH DURING SPEECH.

    Science.gov (United States)

    LANE, H.; AND OTHERS

    SINCE THE 19TH CENTURY, KYMOGRAPHIC RECORDING OF TOTAL AIR FLOW OUT OF THE MOUTH HAS BEEN USED TO DIAGNOSE THE VARYING DURATIONS AND DEGREES OF CONSTRICTIONS OF THE VOCAL TRACT DURING SPEECH. THE PRESENT PROJECT ATTEMPTS TO INTRODUCE A SECOND DIMENSION TO RECORDINGS OF AIR FLOW OUT OF THE MOUTH--NAMELY, CROSS-SECTIONAL AREA OF FLOW--ON THE…

  16. Application of a continuously stirred tank bioreactor (CSTR) for bioremediation of hydrocarbon-rich industrial wastewater effluents

    Energy Technology Data Exchange (ETDEWEB)

    Gargouri, Boutheina; Karray, Fatma; Mhiri, Najla; Aloui, Fathi [Laboratoire des Bioprocedes Environnementaux, Pole d' Excellence Regional AUF-LBPE, Centre de Biotechnologie de Sfax, Universite de Sfax, BP 1117, 3018 Sfax (Tunisia); Sayadi, Sami, E-mail: sami.sayadi@cbs.rnrt.tn [Laboratoire des Bioprocedes Environnementaux, Pole d' Excellence Regional AUF-LBPE, Centre de Biotechnologie de Sfax, Universite de Sfax, BP 1117, 3018 Sfax (Tunisia)

    2011-05-15

    A continuously stirred tank bioreactor (CSTR) was used to optimize feasible and reliable bioprocess system in order to treat hydrocarbon-rich industrial wastewaters. A successful bioremediation was developed by an efficient acclimatized microbial consortium. After an experimental period of 225 days, the process was shown to be highly efficient in decontaminating the wastewater. The performance of the bioaugmented reactor was demonstrated by the reduction of COD rates up to 95%. The residual total petroleum hydrocarbon (TPH) decreased from 320 mg TPH l{sup -1} to 8 mg TPH l{sup -1}. Analysis using gas chromatography-mass spectrometry (GC-MS) identified 26 hydrocarbons. The use of the mixed cultures demonstrated high degradation performance for hydrocarbons range n-alkanes (C10-C35). Six microbial isolates from the CSTR were characterized and species identification was confirmed by sequencing the 16S rRNA genes. The partial 16S rRNA gene sequences demonstrated that 5 strains were closely related to Aeromonas punctata (Aeromonas caviae), Bacillus cereus, Ochrobactrum intermedium, Stenotrophomonas maltophilia and Rhodococcus sp. The 6th isolate was affiliated to genera Achromobacter. Besides, the treated wastewater could be considered as non toxic according to the phytotoxicity test since the germination index of Lepidium sativum ranged between 57 and 95%. The treatment provided satisfactory results and presents a feasible technology for the treatment of hydrocarbon-rich wastewater from petrochemical industries and petroleum refineries.

  17. Application of a continuously stirred tank bioreactor (CSTR) for bioremediation of hydrocarbon-rich industrial wastewater effluents.

    Science.gov (United States)

    Gargouri, Boutheina; Karray, Fatma; Mhiri, Najla; Aloui, Fathi; Sayadi, Sami

    2011-05-15

    A continuously stirred tank bioreactor (CSTR) was used to optimize feasible and reliable bioprocess system in order to treat hydrocarbon-rich industrial wastewaters. A successful bioremediation was developed by an efficient acclimatized microbial consortium. After an experimental period of 225 days, the process was shown to be highly efficient in decontaminating the wastewater. The performance of the bioaugmented reactor was demonstrated by the reduction of COD rates up to 95%. The residual total petroleum hydrocarbon (TPH) decreased from 320 mg TPH l(-1) to 8 mg TPH l(-1). Analysis using gas chromatography-mass spectrometry (GC-MS) identified 26 hydrocarbons. The use of the mixed cultures demonstrated high degradation performance for hydrocarbons range n-alkanes (C10-C35). Six microbial isolates from the CSTR were characterized and species identification was confirmed by sequencing the 16S rRNA genes. The partial 16S rRNA gene sequences demonstrated that 5 strains were closely related to Aeromonas punctata (Aeromonas caviae), Bacillus cereus, Ochrobactrum intermedium, Stenotrophomonas maltophilia and Rhodococcus sp. The 6th isolate was affiliated to genera Achromobacter. Besides, the treated wastewater could be considered as non toxic according to the phytotoxicity test since the germination index of Lepidium sativum ranged between 57 and 95%. The treatment provided satisfactory results and presents a feasible technology for the treatment of hydrocarbon-rich wastewater from petrochemical industries and petroleum refineries.

  18. Methane production from cattle manure supplemented with crude glycerin from the biodiesel industry in CSTR and IBR.

    Science.gov (United States)

    Castrillón, L; Fernández-Nava, Y; Ormaechea, P; Marañón, E

    2013-01-01

    The aim of the present research work was to optimise biogas production from cattle manure by adding crude glycerin from the biodiesel industry. For this purpose, 6%v/v crude glycerin (the optimum amount according to previous research) was added to ground manure and the mixture was sonicated to enhance biodegradability prior to anaerobic co-digestion at 55 °C. Two different reactors were used: continuously stirred (CSTR) and induced bed (IBR). The methanol and pure glycerin contents of the crude glycerin used in this study were 5.6% and 49.4% (w/w), respectively. The best results when operating in CSTR were obtained for an organic loading rate (OLR) of 5.4 kg COD/m(3) day, obtaining 53.2m(3) biogas/t wet waste and 80.7% COD removal. When operating in IBR, the best results were obtained for an OLR of 6.44 kg COD/m(3)day, obtaining 89.6% COD removal and a biogas production of 56.5m(3)/t wet waste.

  19. Simultaneous treatment of raw palm oil mill effluent and biodegradation of palm fiber in a high-rate CSTR.

    Science.gov (United States)

    Khemkhao, Maneerat; Techkarnjanaruk, Somkiet; Phalakornkule, Chantaraporn

    2015-02-01

    A high-rate continuous stirred tank reactor (CSTR) was used to produce biogas from raw palm oil mill effluent (POME) at 55°C at a highest organic loading rate (OLR) of 19 g COD/ld. Physical and chemical pretreatments were not performed on the raw POME. In order to promote retention of suspended solids, the CSTR was installed with a deflector at its upper section. The average methane yield was 0.27 l/g COD, and the biogas production rate per reactor volume was 6.23 l/l d, and the tCOD removal efficiency was 82%. The hydrolysis rate of cellulose, hemicelluloses and lignin was 6.7, 3.0 and 1.9 g/d, respectively. The results of denaturing gradient gel electrophoresis (DGGE) suggested that the dominant hydrolytic bacteria responsible for the biodegradation of the palm fiber and residual oil were Clostridium sp., while the dominant methanogens were Methanothermobacter sp.

  20. Patterned turbulence in liquid metal flow: computational reconstruction of the Hartmann experiment.

    Science.gov (United States)

    Krasnov, Dmitry; Thess, André; Boeck, Thomas; Zhao, Yurong; Zikanov, Oleg

    2013-02-22

    We present results of a numerical analysis of Hartmann's historical experiments on flows of mercury in pipes and ducts under the influence of magnetic fields. The computed critical parameters for the laminar-turbulent transition as well as the friction coefficients are in excellent agreement with Hartmann's data. The simulations provide a first detailed view of the flow structures that are experimentally inaccessible. Novel flow regimes with localized turbulent spots near the sidewalls parallel to the magnetic field and otherwise laminar flow are discovered. We finally suggest how these predictions can be tested in a transparent fluid using optical flow measurement.

  1. Three-phase theory of city traffic: Moving synchronized flow patterns in under-saturated city traffic at signals

    Science.gov (United States)

    Kerner, Boris S.

    2014-03-01

    Three-phase traffic flow theory of city traffic has been developed. Based on simulations of a stochastic microscopic traffic flow model, features of moving synchronized flow patterns (MSP) have been studied, which are responsible for a random time-delayed breakdown of a green-wave (GW) organized in a city. A possibility of GW control leading to the prevention of GW breakdown has been demonstrated. A diagram of traffic breakdown in under-saturated traffic (transition from under- to over-saturated city traffic) at the signal has been found; the diagram presents regions of the average arrival flow rate, within which traffic breakdown can occur, in dependence of parameters of the time-function of the arrival flow rate or/and signal parameters. Physical reasons for a crucial difference between results of classical theory of city traffic and three-phase theory are explained. In particular, we have found that under-saturated traffic at the signal can exist during a long time interval, when the average arrival flow rate is larger than the capacity of the classical theory; the classical capacity is equal to a minimum capacity in three-phase theory. Within a range of the average arrival flow rate between the minimum and maximum signal capacities, under-saturated traffic is in a metastable state with respect to traffic breakdown. We have distinguished the following possible causes for the metastability of under-saturated traffic: (i) The arrival flow rate during the green phase is larger than the saturation flow rate. (ii) The length of the upstream front of a queue at the signal is a finite value. (iii) The outflow rate from a MSP (the rate of MSP discharge) is larger than the saturation flow rate.

  2. Glacial geomorphology of the northwestern Weddell Sea, eastern Antarctic Peninsula continental shelf: Shifting ice flow patterns during deglaciation

    Science.gov (United States)

    Campo, Jennifer M.; Wellner, Julia S.; Domack, Eugene; Lavoie, Caroline; Yoo, Kyu-Cheul

    2017-03-01

    During the Last Glacial Maximum, grounded ice from the expanded Antarctic Peninsula Ice Sheet extended across the continental shelf. Grounded and flowing ice created a distinctive array of glacial geomorphic features on the sea floor, which were then exposed as the ice sheet retreated. The recent disintegration of the northern parts of the Larsen Ice Shelf (Larsen A and B) have permitted acquisition of marine geophysical data in previously inaccessible and unmapped areas. We present a reconstruction of the evolving ice-flow path and ice sheet geometry of the eastern Antarctic Peninsula, with particular focus paid to newly surveyed areas that shed light on the dynamics of a marine-terminating glacial geomorphic environment, where ice shelves play a major role in grounding line stability. Shifting flow directions were mapped in several areas, including across the Seal Nunataks, which divide Larsen A and B, and offshore of Larsen C, indicating flow reorientation that reflects the changing ice sheet geometry as retreat neared the modern coastline. The measured flow indicators in this area reveal comparatively high elongation ratios (> 20), indicating rapid ice flow. Evidence of possible previous ice-shelf collapses are noted near the shelf break, further illustrating the critical, protective effect that ice shelves impart to marine-terminating glacial environments. Modern ice retreat is governed in part by reorganization of flow patterns accompanying grounding line movement; such reorganizations happened in the past and can aid understanding of modern processes.

  3. Heat flow patterns of the North American continent: A discussion of the DNAG Geothermal Map of North America

    Energy Technology Data Exchange (ETDEWEB)

    Blackwell, David D.; Steele, John L.; Carter, Larry C.

    1990-01-01

    The large and small-scale geothermal features of the North American continent and surrounding ocean areas illustrated on the new 1:5,000,000 DNAG Geothermal Map of North America are summarized. Sources for the data included on the map are given. The types of data included are heat flow sites coded by value, contours of heat flow with a color fill, areas of major groundwater effects on regional heat flow, the top-of-geopressure in the Gulf Coast region, temperature on the Dakota aquifer in the midcontinent, location of major hot springs and geothermal systems, and major center of Quaternary and Holocene volcanism. The large scale heat flow pattern that is well known for the conterminous United States and Canada of normal heat flow east of the Cordillera and generally high heat flow west of the front of the Cordillera dominates the continental portion of the map. However, details of the heat flow variations are also seen and are discussed briefly in this and the accompanying papers.

  4. 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.

  5. The annual pattern of sap flow in tow Eucalyptus species established in the vicinity of gold-mine tailings dams in central South Africa

    CSIR Research Space (South Africa)

    Dye, P

    2016-08-01

    Full Text Available of contaminants. The annual pattern of hourly sap flow in four contiguous Eucalyptus dunnii trees (aged three years) was followed over a full year in a species trial situated near Carltonville. The annual pattern of hourly sap flow was also recorded in four...

  6. Patterns of a slow air-water flow in a semispherical container

    DEFF Research Database (Denmark)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.

    2016-01-01

    This numerical study analyzes the development of eddies in a slow steady axisymmetric air-water flow in a sealed semispherical container, driven by a rotating top disk. As the water height, Hw, increases, new flow cells emerge in both water and air. First, an eddy emerges near the axis-bottom int......This numerical study analyzes the development of eddies in a slow steady axisymmetric air-water flow in a sealed semispherical container, driven by a rotating top disk. As the water height, Hw, increases, new flow cells emerge in both water and air. First, an eddy emerges near the axis...... on the air flow. In contrast to flows in cylindrical and conical containers, there is no interaction with Moffatt corner vortices here....

  7. Hydrolysis-acidogenesis of food waste in solid-liquid-separating continuous stirred tank reactor (SLS-CSTR) for volatile organic acid production.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Selvam, Ammaiyappan; Wong, Jonathan W C

    2016-01-01

    The use of conventional continuous stirred tank reactor (CSTR) can affect the methane (CH4) recovery in a two-stage anaerobic digestion of food waste (FW) due to carbon short circuiting in the hydrolysis-acidogenesis (Hy-Aci) stage. In this research, we have designed and tested a solid-liquid-separating CSTR (SLS-CSTR) for effective Hy-Aci of FW. The working conditions were pH 6 and 9 (SLS-CSTR-1 and -2, respectively); temperature-37°C; agitation-300rpm; and organic loading rate (OLR)-2gVSL(-1)day(-1). The volatile fatty acids (VFA), enzyme activities and bacterial population (by qPCR) were determined as test parameters. Results showed that the Hy-Aci of FW at pH 9 produced ∼35% excess VFA as compared to that at pH 6, with acetic and butyric acids as major precursors, which correlated with the high enzyme activities and low lactic acid bacteria. The design provided efficient solid-liquid separation there by improved the organic acid yields from FW.

  8. On-line estimation of the dissolved zinc concentration during ZnS precipitation in a continuous stirred tank reactor (CSTR)

    NARCIS (Netherlands)

    Grootscholten, T.I.M.; Keesman, K.J.; Lens, P.N.L.

    2008-01-01

    In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classical observ

  9. 高温CSTR-中温UASB两级厌氧处理木薯酒精废水%Two-stage anaerobic treatment of cassava ethanol wastewater using thermophilic CSTR and mesophilic UASB

    Institute of Scientific and Technical Information of China (English)

    陈金荣; 谢丽; 罗刚; 周琪

    2011-01-01

    Since cassava ethanol wastewater is characterized by high temperature,high solid content and high organism concentration,the two-stage anaerobic treatment using thermophilic continuous stirred tank reactor (CSTR)and mesophilic upflow anaerobic sludge bed (UASB) has been conducted. Experimental results show that when the influent COD loading of thermophilic CSTR is controlled 14 kg/(m3·d) and COD loading of mesophilic UASB reactor is controlled 3 kg/(m3·d) ,the total removal rates of COD,SS,TN and TP are 94% ,96% ,44% and 87% ,respectively, after the two-stage anaerobic treatment.The life cycle of cassava ethanol production and economic benefits of such wastewater treatment are discussed,indicating that two-stage anaerobic treatment process can not only reduce the pollution resulted from cassava ethanol production, but also create economic benefits from the biogas produced in the course of treatment.%针对木薯酒精废水温度、固体含量及有机物浓度高的特点,采用高温CSTR-中温UASB两级厌氧工艺处理木薯酒精废水.小试结果表明,控制高温CSTR进水COD负荷为14 kg/(m3·d),中温UASB COD负荷为3 kg/(m3·d)时,两级厌氧对COD、SS、溶解性TN、溶解性TP的总去除率分别达94%、96%、44%和87%.对木薯酒精生产周期和废水处理经济效益的分析表明,采用两级厌氧工艺处理木薯酒精废水,不仅削减了木薯酒精生产过程中产生的污染物,其处理过程中产生的沼气还带来了一定的经济效益.

  10. Flow-through synthesis on Teflon-patterned paper to produce peptide arrays for cell-based assays.

    Science.gov (United States)

    Deiss, Frédérique; Matochko, Wadim L; Govindasamy, Natasha; Lin, Edith Y; Derda, Ratmir

    2014-06-16

    A simple method is described for the patterned deposition of Teflon on paper to create an integrated platform for parallel organic synthesis and cell-based assays. Solvent-repelling barriers made of Teflon-impregnated paper confine organic solvents to specific zones of the patterned array and allow for 96 parallel flow-through syntheses on paper. The confinement and flow-through mixing significantly improves the peptide yield and simplifies the automation of this synthesis. The synthesis of 100 peptides ranging from 7 to 14 amino acids in length gave over 60% purity for the majority of the peptides (>95% yield per coupling/deprotection cycle). The resulting peptide arrays were used in cell-based screening to identify 14 potent bioactive peptides that support the adhesion or proliferation of breast cancer cells in a 3D environment. In the future, this technology could be used for the screening of more complex phenotypic responses, such as cell migration or differentiation.

  11. Bifurcation Characteristics Analysis of Methane Combustion Process in CSTR%CSTR系统中甲烷燃烧过程的分岔特性分析

    Institute of Scientific and Technical Information of China (English)

    梁运涛; 曾文

    2011-01-01

    Bifurcation characteristics analysis of the combustion process of methane in a continuously-flow well-stirred tank reactor (CSTR) was carried out. The detailed chemical reaction mechanism of methane was adopted. The effects of system pressure, excessive air coefficient, system temperature and residence time on the bifurcation characteristics of the combustion process were discussed with system temperature and residence time as bifurcation parameters, respectively. There are two ignition points, namely partial ignition point and full ignition point, and three stages, including ignited branch, full ignited branch and extinguished branch, in the whole combustion process. When system temperature is adopted as bifurcation parameter, with the increase of system pressure, residence time gets prolonged, excessive air coefficient increasing, full ignition temperature decreases. When residence time is adopted as bifurcation parameter, with the increase of system pressure and temperature, residence time of full ignition is shortened. However, excessive air coefficient has little effect on residence time.%运用分岔理论对连续流动均匀搅拌反应器(CSTR)中甲烷燃烧过程的分岔特性进行了详细分析,采用了甲烷的详细化学反应机理.分别以系统温度、滞留时间为分岔参数,详细讨论了CSTR系统的各种工况(系统压力、混合气过量空气系数、系统温度及滞留时间)对甲烷燃烧过程分岔特性的影响.结果表明,在甲烷的整个燃烧过程中,出现了双着火点,即部分着火点和完全着火点;同时,出现了3个阶段,即部分着火阶段、完全着火阶段和熄火阶段.当以系统温度为分岔参数时,随着系统压力的升高、滞留时间的延长、过量空气系数的增加,甲烷的完全着火温度也随之降低.当以滞留时间为分岔参数时,随着系统温度、系统压力的升高,甲烷发生完全着火所需要的滞留时问随之缩短

  12. Patterns of Foreign Direct Investment Flows and Trade-Investment Inter-Linkages in Southern Africa : Linking Middle-Income and Low-Income Neighbors

    OpenAIRE

    Isik, Gozde; YOSHINO, Yutaka

    2010-01-01

    This report discusses the patterns of foreign direct investment flows and trade-investment inter-linkages in Southern Africa. It will discuss how cross-border investment flows create a possible channel of growth spillover from South Africa and other MICs to LICs in the subregion, and identify the roles of subregional trade and investment flows in generating these neighborhood effects with ...

  13. Geophysical controls of aquifer-river exchange flow patterns in a UK lowland meandering river.

    Science.gov (United States)

    Dara, Rebwar; Krause, Stefan; Rivett, Michael

    2016-04-01

    The deposition of fine particles (clay and silt) and organic matters in alluvial sediments can substantially reduce the permeability of streambed sediments and extend towards the wider floodplain. The resulting hydraulic conductivity patterns within the streambed and floodplain have been shown to control both location as well as intensity of hyporheic exchange in many lowland rivers. The aim of the study is to investigate the variability in streambed permeability fields in an unprecedented spatial resolution and quantify the impacts on controlling hyporheic exchange fluxes in the River Tern, a UK lowland meandering stream. Geophysical surveys were conducted deploying Ground Penetrating Radar (GPR) in conjunction with geological information derived from core logs and bank exposures for mapping shallow subsurface structural heterogeneity. The GPR survey deployed a pulse EKKO pro equipped with a shielded 250 MHz antenna. For the floodplain survey, GPR profiles of 12 NE-SW and 6 NW- SE orientation profiles were taken creating a raster of approximately 10 m. The riparian terrestrial GPR surveys were accompanied by a longitudinal in channel GPR survey for which the antenna was deployed on a floating device. At locations identified to be representative for the range of streambed hydrofacies identified by GPR in investigated stream reach, multi-level mini-piezometer networks were installed in the streambed for monitoring groundwater-surface water exchange fluxes, and conducting dilution tracer tests for quantification of residence time distributions at the aquifer-river interface. Quasi-three-dimensional GPR profiles from closely spaced grids of 2D GPR data of floodplain deposits indicated a range of different radar facies and helped to delineate the type and extend of high and low conductive materials. The results of longitudinal GPR survey along a 240 m section of the river channel revealed that areas rich in low conductivity layers such as organic peat and clay lenses

  14. The pretzel sign: angiographic pattern of tortuous intra-aneurysmal blood flow in a giant serpentine aneurysm.

    LENUS (Irish Health Repository)

    Fanning, N F

    2012-02-03

    Giant serpentine aneurysms (GSAs) form a specific subgroup of giant cerebral aneurysms that have pathognomonic angiographic features. We report the angiographic findings of a GSA demonstrating a striking convoluted dynamic flow pattern, which we have called the \\'pretzel sign\\'. The aneurysm was successfully treated by permanent occlusion of the parent vessel using a detachable balloon. GSAs should be identified prior to treatment in view of their particular management requirements.

  15. Linking rainfall-induced landslides with debris flows runout patterns towards catchment scale hazard assessment

    Science.gov (United States)

    Fan, Linfeng; Lehmann, Peter; McArdell, Brian; Or, Dani

    2017-03-01

    Debris flows and landslides induced by heavy rainfall represent an ubiquitous and destructive natural hazard in steep mountainous regions. For debris flows initiated by shallow landslides, the prediction of the resulting pathways and associated hazard is often hindered by uncertainty in determining initiation locations, volumes and mechanical state of the mobilized debris (and by model parameterization). We propose a framework for linking a simplified physically-based debris flow runout model with a novel Landslide Hydro-mechanical Triggering (LHT) model to obtain a coupled landslide-debris flow susceptibility and hazard assessment. We first compared the simplified debris flow model of Perla (1980) with a state-of-the art continuum-based model (RAMMS) and with an empirical model of Rickenmann (1999) at the catchment scale. The results indicate that predicted runout distances by the Perla model are in reasonable agreement with inventory measurements and with the other models. Predictions of localized shallow landslides by LHT model provides information on water content of released mass. To incorporate effects of water content and flow viscosity as provided by LHT on debris flow runout, we adapted the Perla model. The proposed integral link between landslide triggering susceptibility quantified by LHT and subsequent debris flow runout hazard calculation using the adapted Perla model provides a spatially and temporally resolved framework for real-time hazard assessment at the catchment scale or along critical infrastructure (roads, railroad lines).

  16. Research on Flow Pattern of Nitrogen Tetroxide Liquid in the Different Bend Radii Pipes

    National Research Council Canada - National Science Library

    Hao, Pengfei; Si, Wenji; Zhang, Hui; Zhang, Ping; Yue, Shouti

    2016-01-01

    .... For this reason, the research of the different bending radii vaporized fluid conditions for optimizing the piping and precise the filling flow is significant. In this paper, the MIXTURE mixed flow model is used to achieve the numerical simulation the pipelines filling of the three different bending radii, it still have not solved the mass transfer pr...

  17. A Study of the Flow Patterns of Expanding Impurity Aerosol Following a Disruption Event in a Fusion Reactor

    Science.gov (United States)

    Majumdar, Rudrodip

    The current study focuses on the adiabatic expansion of aerosol impurity in the post-disruption and thermal quench scenario inside the vacuum chamber of a fusion reactor. A pulsed electrothermal plasma (ET) capillary source has been used as a source term simulating the surface ablation of the divertor or other interior critical components of a tokamak fusion reactor under hard disruption-like conditions. The capillary source generates particulates from wall evaporation by depositing transient radiant high heat flux onto the inner liner of the capillary. The particulates form a plasma jet moving towards the capillary exit at high speed and high pressure. The first chapter discusses briefly the relevance of the study pertaining to the impurities in a fusion reactor based on the work available in the form of published literature. The second chapter discusses briefly the operating principle of a pulsed electrothermal plasma source (PEPS), the virtual integration of PEPS with 1-D electrothermal plasma flow solver ETFLOW and the use of capillary plasma sources in various industrial applications. The third chapter discusses about primitive computational work, backed by the data from actual electrothermal source experiments from the in-house facility "PIPE" (Plasma Interactions with Propellants Experiment), that shows the supersonic bulk flow patterns for the temperature, density, pressure, bulk velocity and the flow Mach number of the impurity particulates as they get ejected as a high-pressure, high-temperature and hyper-velocity jet from the simulated source term. It also shows the uniform steady-state subsonic expansion of bulk aerosol inside the expansion chamber. The fourth chapter discusses scaling laws in 1-D for the aforesaid bulk plasma parameters for ranges of axial length traversed by the flow, so that one can retrieve the flow parameters at some preferred locations. The fifth chapter discusses the effect of temperature and the non--linearity of the adiabatic

  18. Effect of feed flow pattern on the distribution of permeate fluxes in desalination by direct contact membrane distillation

    KAUST Repository

    Soukane, Sofiane

    2017-05-31

    The current study aims to highlight the effect of flow pattern on the variations of permeate fluxes over the membrane surface during desalination in a direct contact membrane distillation (DCMD) flat module. To do so, a three dimensional (3D) Computational Fluid Dynamics (CFD) model with embedded pore scale calculations is implemented to predict flow, heat and mass transfer in the DCMD module. Model validation is carried out in terms of average permeate fluxes with experimental data of seawater desalination using two commercially available PTFE membranes. Average permeate fluxes agree within 6% and less with experimental values without fitting parameters. Simulation results show that the distribution of permeate fluxes and seawater salinity over the membrane surface are strongly dependent on momentum and heat transport and that temperature and concentration polarization follow closely the flow distribution. The analysis reveals a drastic effect of recirculation loops and dead zones on module performance and recommendations to improve MD flat module design are drawn consequently.

  19. Numerical investigation of flow and thermal pattern in unbounded flow using nanofluid - Case study: Laminar 2-D plane jet

    Directory of Open Access Journals (Sweden)

    Armaghani Taher

    2016-01-01

    Full Text Available In this article, a numerical study is carried out to analyze the effect of nanoparticle volume fraction over flow and thermal characteristics of laminar 2-D plane jet. Al2O3-water and TiO2-water nanofluids are considered in this investigation with lowest and highest values of particle volume concentration equals to 0 and 0.02 respectively. This paper propose four correlations for describing the relation between the solid volume fraction, δt and δu. The results show that the cross stream thermal diffusion depth and cross stream hydraulic diffusion depth are increased when particles volume concentration is increased and mean temperature and mean velocity decreases when the solid volume fraction is increased. The effects of nanoparticle volume fraction in velocity and temperature time histories are also studied and discussed.

  20. Geological evidence for the geographical pattern of mantle return flow and the driving mechanism of plate tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, W.

    1982-08-10

    Tectonic features at the earth's surface can be used to test models for mantle return flow and to determine the geographic pattern of this flow. A model with shallow return and deep continental roots places the strongest constraints on the geographical pattern of return flow and predicts recognizable surface manifestations. Because of the progressive shrinkage of the Pacific (averaging 0.5 km/sup 2//yr over the last 180 m.y.) this model predicts upper mantle outflow through the three gaps in the chain of continents rimming the Pacific (Carribbean, Drake Passage, Australian-Antartic gap). In this model, upper mantle return flow streams originating at the western Pacific trenches and at the Java Trench meet south of Australia, filling in behind this rapidly northward-moving continent and provding an explanation for the negative bathymetric and gravity anomalies of the 'Australian-Antarctic-Discordance'. The long-continued tectonic movements toward the east that characterize the Caribbean and the eastenmost Scotia Sea may be produced by viscous coupling to the predicted Pacific outflow through the gaps, and the Caribbean floor slopes in the predicted direction. If mantle outflow does not pass through the gaps in the Pacific perimeter, it must pass beneath three seismic zones (Central America, Lesser Antiles, Scotia Sea); none of these seismic zones shows foci below 200 km. Mantle material flowing through the Caribbean and Drake Passage gaps would supply the Mid-Atlantic Ridge, while the Java Trench supplies the Indian Ocean ridges, so that deep-mantle upwellings need not be centered under spreading ridges and therefore are not required to move laterally to follow ridge migrations. The analysis up to this point suggests that upper mantle return flow is a response to the motion of the continents. The second part of the paper suggest driving mechanism for the plate tectonic process which may explain why the continents move.

  1. UNDERSTANDING THE POPULATION GENETIC STRUCTURE OF GLEDITSIA TRIACANTHOS L.: THE SCALE AND PATTERN OF POLLEN GENE FLOW.

    Science.gov (United States)

    Schnabel, Andrew; Hamrick, J L

    1995-10-01

    Spatial and temporal patterns of gene flow determine the extent to which populations can differentiate from one another as a result of natural selection or genetic drift. In this study, we investigated pollen-mediated gene flow in two eastern Kansas populations of the subdioecious tree species, Gleditsia triacanthos L. (Leguminosae), or honeylocust. In 2 yr at each site, we used paternity-exclusion analysis to estimate the proportion of seeds sired by immigrant pollen. We also used a single-parent and parent-pair exclusion analysis on naturally established seedlings and saplings to estimate gene flow into one site over a 12-yr period and into the second site over a 22-yr period. Results of both analyses showed high minimum estimates of pollen gene flow into each site (17%-30%). In each population, we found significantly less gene flow in years of high fruit production than in years of low fruit production, but in one population, we observed little variation in gene-flow rates among age classes of seedlings and saplings. The level of pollen gene flow showed weak negative dependence on the relative isolation distances of the maternal trees sampled (140-240 m at one site vs. 85-120 m at the second site), and gene-flow estimates from naturally established juveniles were very similar at the two sites. Within populations, a multiple regression model showed that maximum-likelihood estimates of male fertility were negatively associated with distances between mates and positively associated with male size as measured by stem diameter. In neither population, however, did the regression explain more than 16% of the total variation in male fertilities. © 1995 The Society for the Study of Evolution.

  2. Hyporheic flow and dissolved oxygen distribution in fish nests: The effects of open channel velocity, permeability patterns, and groundwater upwelling

    Science.gov (United States)

    Cardenas, M. Bayani; Ford, Aimee E.; Kaufman, Matthew H.; Kessler, Adam J.; Cook, Perran L. M.

    2016-12-01

    Many fish lay their eggs in nests, or redds, which they construct in sediment. The viability of eggs depends on many factors, particularly their oxygenation. Because dissolved oxygen is typically saturated within the stream channel, the dissolved oxygen distribution within the redd depends on whether or not hyporheic flow and transport occur within the sediment. We conducted a series of flume and numerical flow and age transport modeling experiments with the aim of understanding the effects of salmonid redds on the hyporheic transport of young oxygenated water. Hyporheic flow was visualized directly through dye injections. Dissolved oxygen throughout the fish nest was measured using a planar optode. Experiments were conducted at various open channel flow velocities in order to understand their effect on dissolved oxygen, and computational simulations considered various sediment textures and ambient groundwater upwelling rates to add process-level insight. We found that, as also shown by previous studies, the redd topography induces multiscale hyporheic flow that effectively flushes the egg pocket location with younger presumably oxygenated water; older water upwells and forms anoxic zones. This pattern persists even at the lowest channel flow rates and at small upwelling velocities of older ambient groundwater which splits the multiscale hyporheic flow cells into isolated pockets. Large groundwater upwelling rates can shut down all the hyporheic flushing. The relatively coarse texture of the redd further promotes hyporheic flushing of the redd sediment with oxygenated water. Thus, redd morphology and sediment texture optimally combine to induce hyporheic exchange flow that delivers young oxygenated water to the egg pocket.

  3. Comparison of the aerodynamics of bridge cables with helical fillets and a pattern-indented surface in normal flow

    DEFF Research Database (Denmark)

    Kleissl, Kenneth; Georgakis, Christos

    2011-01-01

    -wind induced vibrations (RWIVs). The modifications are based on re-search undertaken predominantly in Europe and Japan, with two different systems prevailing; HDPE tubing fitted with helical surface fillets and HDPE tubing with pattern-indented sur-faces. In the US and Europe, helical fillets dominate, whilst...... pattern indented surfaces are more common in Asia. Research into the effectiveness of helical fillets and pattern-indented surfaces has shown that, besides their potential to suppress rain-wind induced vibrations, they are also modestly reducing drag forces at design wind velocities. This is of particular...... that different researchers, in different facilities, with varying wind-tunnel flow characteristics and performance, have developed each separately. As part of a comprehensive review of the aerodynamics of existing cable surface modifica-tions, the resulting static force coefficients obtained from wind...

  4. Experimental investigation of effect of flow attack angle on thermohydraulic performance of air flow in a rectangular channel with discrete V-pattern baffle on the heated plate

    Directory of Open Access Journals (Sweden)

    Raj Kumar

    2016-05-01

    Full Text Available In this work, the effect of angle of attack ( α a of the discrete V-pattern baffle on thermohydraulic performance of rectangular channel has been studied experimentally. The baffle wall was constantly heated and the other three walls of the channel were kept insulated. The experimentations were conducted to collect the data on Nusselt number ( N u b and friction factor ( f b by varying the Reynolds number (Re = 3000–21,000 and angle of attack ( α a from 30° to 70°, for the kept values of relative baffle height ( H b / H = 0 . 50 , relative pitch ratio ( P b / H = 1 . 0 , relative discrete width ( g w / H b = 1 . 5 and relative discrete distance ( D d / L v = 0 . 67 . As compared to the smooth wall, the V-pattern baffle roughened channel enhances the Nusselt number ( N u b and friction factor ( f b by 4.2 and 5.9 times, respectively. The present discrete V-pattern baffle shapes with angle of attack ( α a of 60° equivalent to flow Reynolds number of 3000 yields the greatest thermohydraulic performance. Discrete V-pattern baffle has improved thermal performance as compared to other baffle shapes’ rectangular channel.

  5. Fluid Flow Patterns During Production from Gas Hydrates in the Laboratory compared to Field Settings: LARS vs. Mallik

    Science.gov (United States)

    Strauch, B.; Heeschen, K. U.; Priegnitz, M.; Abendroth, S.; Spangenberg, E.; Thaler, J.; Schicks, J. M.

    2015-12-01

    The GFZ's LArge Reservoir Simulator LARS allows for the simulation of the 2008 Mallik gas hydrate production test and the comparison of fluid flow patterns and their driving forces. Do we see the gas flow pattern described for Mallik [Uddin, M. et al., J. Can. Petrol Tech, 50, 70-89, 2011] in a pilot scale test? If so, what are the driving forces? LARS has a network of temperature sensors and an electric resistivity tomography (ERT) enabling a good spatial resolution of gas hydrate occurrences, water and gas distribution, and changes in temperature in the sample. A gas flow meter and a water trap record fluid flow patterns and a backpressure valve has controlled the depressurization equivalent to the three pressure stages (7.0 - 5.0 - 4.2 MPa) applied in the Mallik field test. The environmental temperature (284 K) and confining pressure (13 MPa) have been constant. The depressurization induced immediate endothermic gas hydrate dissociation until re-establishment of the stability conditions by a consequent temperature decrease. Slight gas hydrate dissociation continued at the top and upper lateral border due to the constant heat input from the environment. Here transport pathways were short and permeability higher due to lower gas hydrate saturation. At pressures of 7.0 and 5.0 MPa the LARS tests showed high water flow rates and short irregular spikes of gas production. The gas flow patterns at 4.2 MPa and 3.0MPa resembled those of the Mallik test. In LARS the initial gas surges overlap with times of hydrate instability while water content and lengths of pathways had increased. Water production was at a minimum. A rapidly formed continuous gas phase caused the initial gas surges and only after gas hydrate dissociation decreased to a minimum the single gas bubbles get trapped before slowly coalescing again. In LARS, where pathways were short and no additional water was added, a transport of microbubbles is unlikely to cause a gas surge as suggested for Mallik.

  6. Changes in air flow patterns using surfactants and thickeners during air sparging: bench-scale experiments.

    Science.gov (United States)

    Kim, Juyoung; Kim, Heonki; Annable, Michael D

    2015-01-01

    Air injected into an aquifer during air sparging normally flows upward according to the pressure gradients and buoyancy, and the direction of air flow depends on the natural hydrogeologic setting. In this study, a new method for controlling air flow paths in the saturated zone during air sparging processes is presented. Two hydrodynamic parameters, viscosity and surface tension of the aqueous phase in the aquifer, were altered using appropriate water-soluble reagents distributed before initiating air sparging. Increased viscosity retarded the travel velocity of the air front during air sparging by modifying the viscosity ratio. Using a one-dimensional column packed with water-saturated sand, the velocity of air intrusion into the saturated region under a constant pressure gradient was inversely proportional to the viscosity of the aqueous solution. The air flow direction, and thus the air flux distribution was measured using gaseous flux meters placed at the sand surface during air sparging experiments using both two-, and three-dimensional physical models. Air flow was found to be influenced by the presence of an aqueous patch of high viscosity or suppressed surface tension in the aquifer. Air flow was selective through the low-surface tension (46.5 dyn/cm) region, whereas an aqueous patch of high viscosity (2.77 cP) was as an effective air flow barrier. Formation of a low-surface tension region in the target contaminated zone in the aquifer, before the air sparging process is inaugurated, may induce air flow through the target zone maximizing the contaminant removal efficiency of the injected air. In contrast, a region with high viscosity in the air sparging influence zone may minimize air flow through the region prohibiting the region from de-saturating.

  7. Carbon flow pattern in the forest zones of Nigeria as influenced by ...

    African Journals Online (AJOL)

    use

    COPATH, an acronym for Total Carbon Flow from Conversion to Agriculture,. Pasture, Harvest ... means to achieve reduced greenhouse gas (GHG) emissions as well as .... vegetation change, none of the natural factors is known to be able to ...

  8. PIV MEASUREMENT OF THE GAS-SOLID FLOW PATTERN IN A CFB RISER

    Institute of Scientific and Technical Information of China (English)

    Shi Hui-xian; Wang Qin-hui; Wang Can-xing; Luo Zhong-yang; Cen Ke-fa

    2003-01-01

    Particle Imaging Velocimetry (PIV) is a valuable measuring tool for studying multiphase flows, such as liquid-gas and gas-solid flow. It can be used to carry out many hydrodynamic studies, in particular, to determine accurately the gas-solid flow structure in CFB (Circulating Fluidized Beds). In this paper, the technique characteristics was described in applying the PIV to measure the gas-solid flow in circulating fluidized beds. A primary experiment was completed on a CFB unit with the PIV, yielding the velocity vector fields of high-density particles for different gas-solid superficial velocities and solid recycle rates. Velocities of the transported particles were calculated with cross-correlation method. The major factors influencing the successful measurement of particle velocity with the PIV technique were also described.

  9. Influence of through-flow on linear pattern formation properties in binary mixture convection

    CERN Document Server

    Jung, C; Büchel, P; Jung, Ch.

    1996-01-01

    We investigate how a horizontal plane Poiseuille shear flow changes linear convection properties in binary fluid layers heated from below. The full linear field equations are solved with a shooting method for realistic top and bottom boundary conditions. Through-flow induced changes of the bifurcation thresholds (stability boundaries) for different types of convective solutions are deter- mined in the control parameter space spanned by Rayleigh number, Soret coupling (positive as well as negative), and through-flow Reynolds number. We elucidate the through-flow induced lifting of the Hopf symmetry degeneracy of left and right traveling waves in mixtures with negative Soret coupling. Finally we determine with a saddle point analysis of the complex dispersion relation of the field equations over the complex wave number plane the borders between absolute and convective instabilities for different types of perturbations in comparison with the appropriate Ginzburg-Landau amplitude equation approximation. PACS:47.2...

  10. Robust fuzzy output feedback controller for affine nonlinear systems via T-S fuzzy bilinear model: CSTR benchmark.

    Science.gov (United States)

    Hamdy, M; Hamdan, I

    2015-07-01

    In this paper, a robust H∞ fuzzy output feedback controller is designed for a class of affine nonlinear systems with disturbance via Takagi-Sugeno (T-S) fuzzy bilinear model. The parallel distributed compensation (PDC) technique is utilized to design a fuzzy controller. The stability conditions of the overall closed loop T-S fuzzy bilinear model are formulated in terms of Lyapunov function via linear matrix inequality (LMI). The control law is robustified by H∞ sense to attenuate external disturbance. Moreover, the desired controller gains can be obtained by solving a set of LMI. A continuous stirred tank reactor (CSTR), which is a benchmark problem in nonlinear process control, is discussed in detail to verify the effectiveness of the proposed approach with a comparative study.

  11. A CSTR-hollow-fiber system for continuous hydrolysis of proteins. Factors affecting long-term stability of the reactor.

    Science.gov (United States)

    Deeslie, W D; Cheryan, M

    1982-01-01

    Factors affecting the long-term operational stability of a CSTR-hollow-fiber reactor for continuous hydrolysis of proteins were studied. The activity declined in a stepwise manner during a run. Declining from 92% conversion to 60% conversion in about ten hours at a space time of four minutes. Initial decay appears to be due to leakage of small active fragments of the enzyme mixture (Pronase) through the membrane, and later decay due to thermal degradation and loss of activators such as calcium through the membrane. The rate of buildup of unconverted substrate in the reaction vessel was controlled by operational variables, but did not appear to affect the reactor output or the operation of the reactor. The decay of the reactor could be partially compensated for by appropriate manipulation of the space-time variables.

  12. A Stable Control of a Cstr with Input Multiplicities Using Artificial Neural Network Based Narma-l2

    Directory of Open Access Journals (Sweden)

    Prabhaker Reddy Ginuga

    2014-01-01

    Full Text Available In this paper, the Neural network based NARMA-L2 controller is analyzed to an isothermal continuous stirred tank reactor (CSTR which exhibits input multiplicities in space velocity on product of B. i.e., two values of space velocity will give the same value of product B. The Performance of Neural network based NARMA-L2 controller and conventional PI controller have been evaluated through simulation studies. As the NARMA-L2 controller provides always the two values of space velocity for control action and by selecting the value nearer to the operating point, it is found to give stable and better responses than conventional PI controller. The PI controller results in unstable condition or switch over from initial lower input space velocity to higher input space velocity vice versa. Thus, NARMA-L2 controller is found to overcome the control problems of PI controller due to the input multiplicities.

  13. CSTR+UASB+SBR+Fenton组合工艺处理酒精废水的应用

    Institute of Scientific and Technical Information of China (English)

    李星华

    2016-01-01

    某生物质能源集团以木薯为原料生产燃料乙醇,产生的废水具有高浓度有机物和悬浮物,生化性好等特点。结果表明:采用CSTR+UASB+SBR+Fenton组合工艺能有效去除该类型废水中的污染物。该工艺稳定性强,处理效果好,出水达到《GB8978-1996 污水综合排放标准》一级标准的水污染物排放限值。CODCr、BOD5、NH3-N、SS去除率分别为99.88%、99.95%、99.13%、99.90%。

  14. Vacuum-assisted fluid flow in microchannels to pattern substrates and cells.

    Science.gov (United States)

    Shrirao, Anil B; Kung, Frank H; Yip, Derek; Cho, Cheul H; Townes-Anderson, Ellen

    2014-09-01

    Substrate and cell patterning are widely used techniques in cell biology to study cell-to-cell and cell-substrate interactions. Conventional patterning techniques work well only with simple shapes, small areas and selected bio-materials. This paper describes a method to distribute cell suspensions as well as substrate solutions into complex, long, closed (dead-end) polydimethylsiloxane (PDMS) microchannels using negative pressure. Our method builds upon a previous vacuum-assisted method used for micromolding (Jeon et al 1999 Adv. Mater 11 946) and successfully patterned collagen-I, fibronectin and Sal-1 substrates on glass and polystyrene surfaces, filling microchannels with lengths up to 120 mm and covering areas up to 13 × 10 mm(2). Vacuum-patterned substrates were subsequently used to culture mammalian PC12 and fibroblast cells and amphibian neurons. Cells were also patterned directly by injecting cell suspensions into microchannels using vacuum. Fibroblast and neuronal cells patterned using vacuum showed normal growth and minimal cell death indicating no adverse effects of vacuum on cells. Our method fills reversibly sealed PDMS microchannels. This enables the user to remove the PDMS microchannel cast and access the patterned biomaterial or cells for further experimental purposes. Overall, this is a straightforward technique that has broad applicability for cell biology.

  15. Vacuum-assisted Fluid Flow in Microchannels to Pattern Substrates and Cells

    Science.gov (United States)

    Shrirao, Anil B.; Kung, Frank H.; Yip, Derek; Cho, Cheul H.; Townes-Anderson, Ellen

    2014-01-01

    Substrate and cell patterning are widely used techniques in cell biology to study cell-to-cell and cell-to-substrate interactions. Conventional patterning techniques work well only with simple shapes, small areas and selected bio-materials. This paper describes a method to distribute cell suspensions as well as substrate solutions into complex, long, closed (dead-end) polydimethylsiloxane (PDMS) microchannels using negative pressure. Our method builds upon a previous vacuum-assisted method used for micromolding (Jeon, Choi et al. 1999) and successfully patterned collagen-I, fibronectin and Sal-1 substrates on glass and polystyrene surfaces, filling microchannels with lengths up to 120 mm and covering areas up to 13 × 10 mm2. Vacuum-patterned substrates were subsequently used to culture mammalian PC12 and fibroblast cells and amphibian neurons. Cells were also patterned directly by injecting cell suspensions into microchannels using vacuum. Fibroblast and neuronal cells patterned using vacuum showed normal growth and minimal cell death indicating no adverse effects of vacuum on cells. Our method fills reversibly sealed PDMS microchannels. This enables the user to remove the PDMS microchannel cast and access the patterned biomaterial or cells for further experimental purposes. Overall, this is a straightforward technique that has broad applicability for cell biology. PMID:24989641

  16. Heat flow pattern at the Chicxulub impact crater, northern Yucatan, Mexico

    Science.gov (United States)

    Espinosa-Cardeña, J. M.; Campos-Enríquez, J. O.; Unsworth, M.

    2016-02-01

    Along an east-west profile crossing the Chicxulub impact structure in northern Yucatán, México, Curie depths were obtained from statistical-spectral analysis of a grid of aeromagnetic data (256 km wide and 600 km long). These depths were corrected for flight height and depth to the sea floor to determine the geothermal gradient, assuming a temperature of 580 °C for the Curie temperature. Heat flow was then calculated from the geothermal gradients using a value of 2.67 W/m-K for the mean crustal thermal conductivity. The results show a conspicuous heat flow high above on the impact basin. In this location, the heat flow is 80 mW/m2 approximately. Available offshore estimates of the depth to the crustal magnetic source bases, on the northern Yucatán platform, and onshore heat flow determination on 8 shallow bore holes, and in a 1511 m deep one, support the existence of this major high heat flow anomaly associated with the impact crater. This high heat flow might be related to the impact through: (1) an uplift of the crystalline basement rocks in the center of the crater; and (2) impact induced radioactive element concentration into the crust below the impact structure. Higher thermal conductivities at the lower crust might also play a key role. Available seismological and thermal property data are compatible with these mechanisms.

  17. Flow pattern-based mass and heat transfer and frictional drag of gas-non-Newtonian liquid flow in helical coil: two- and three-phase systems

    Science.gov (United States)

    Thandlam, Anil Kumar; Das, Chiranjib; Majumder, Subrata Kumar

    2016-08-01

    Investigation of wall-liquid mass transfer and heat transfer phenomena with gas-Newtonian and non-Newtonian fluids in vertically helical coil reactor have been reported in this article. Experiments were conducted to investigate the effect of various dynamic and geometric parameters on mass and heat transfer coefficients in the helical coil reactor. The flow pattern-based heat and mass transfer phenomena in the helical coil reactor are highlighted at different operating conditions. The study covered a wide range of geometric parameters such as diameter of the tube (d t ), diameter of the coil (D c ), diameter of the particle (d p ), pitch difference (p/D c ) and concentrations of non-Newtonian liquid. The correlation models for the heat and mass transfer coefficient based on the flow pattern are developed which may be useful in process scale-up of the helical coil reactor for industrial application. The frictional drag coefficient was also estimated and analyzed by mass transfer phenomena based on the electrochemical method.

  18. Assessment of spatial and temporal patterns of green and blue water flows in inland river basins in Northwest China

    Directory of Open Access Journals (Sweden)

    C. F. Zang

    2012-03-01

    Full Text Available In arid and semi-arid regions freshwater resources have become scarcer with increasing demands from socio-economic development and population growth. Until recently, water research and management in these has mainly focused on blue water but ignored green water. Here we report on spatial and temporal patterns of both blue and green water flows simulated by the Soil and Water Assessment Tool (SWAT for the Heihe river basin, the second largest inland river basin in Northwest China. Calibration and validation at two hydrological stations show good performance of the SWAT model in modelling hydrological processes. The total green and blue water flows were 22.09 billion m3 in the 2000s for the Heihe river basin. Blue water flows are larger in upstream sub-basins than in downstream sub-basins mainly due to high precipitation and large areas of glaciers in upstream. Green water flows are distributed more homogeneously among different sub-basins. The green water coefficient was 88.0% in the 2000s for the entire river basin, varying from around 80–90% in up- and mid-stream sub-basins to above 95% in downstream sub-basins. This is much higher than reported green water coefficient in many other river basins. The spatial patterns of green water coefficient were closely linked to dominant land covers (e.g. glaciers in upstream and desert in downstream and climate conditions (e.g. high precipitation in upstream and low precipitation in downstream. There are no clear consistent historical trends of change in green and blue water flows and green water coefficient at both the river basin and sub-basin levels. This study provides insights into green and blue water endowments for the entire Heihe river basin at sub-basin level. The results are helpful for formulating reasonable water policies to improve water resources management in the inland river basins of China.

  19. Validation of a simple method for predicting the disinfection performance in a flow-through contactor.

    Science.gov (United States)

    Pfeiffer, Valentin; Barbeau, Benoit

    2014-02-01

    Despite its shortcomings, the T10 method introduced by the United States Environmental Protection Agency (USEPA) in 1989 is currently the method most frequently used in North America to calculate disinfection performance. Other methods (e.g., the Integrated Disinfection Design Framework, IDDF) have been advanced as replacements, and more recently, the USEPA suggested the Extended T10 and Extended CSTR (Continuous Stirred-Tank Reactor) methods to improve the inactivation calculations within ozone contactors. To develop a method that fully considers the hydraulic behavior of the contactor, two models (Plug Flow with Dispersion and N-CSTR) were successfully fitted with five tracer tests results derived from four Water Treatment Plants and a pilot-scale contactor. A new method based on the N-CSTR model was defined as the Partially Segregated (Pseg) method. The predictions from all the methods mentioned were compared under conditions of poor and good hydraulic performance, low and high disinfectant decay, and different levels of inactivation. These methods were also compared with experimental results from a chlorine pilot-scale contactor used for Escherichia coli inactivation. The T10 and Extended T10 methods led to large over- and under-estimations. The Segregated Flow Analysis (used in the IDDF) also considerably overestimated the inactivation under high disinfectant decay. Only the Extended CSTR and Pseg methods produced realistic and conservative predictions in all cases. Finally, a simple implementation procedure of the Pseg method was suggested for calculation of disinfection performance.

  20. 蛇管与夹套冷却CSTR温度双重控制%Temperature dual control of CSTR with coil cooler and jacket cooler

    Institute of Scientific and Technical Information of China (English)

    王再英; 王正宇

    2012-01-01

    The CSTR is important chemical industrys. The temperature dual temperature control system solution is proposed for CSTR with coil cooling and jacket cooling after researching the insufficiency the single loop control using only one manipulating variable and to be incapable satisfy the dynamic and static performance simultaneity. Under the dual control system, the coil cooler eliminates quickly the error and the temperature returns to set value as soon as the CSTR temperature error appear, then the coil cooler load variety for the CSTR cooling is replaced gradually by the more efficient jacket cooler, namely, CSTR temperature is controlled by the manipulating variable possessing finer dynamic property (coil cooler) in dynamic process, transition shorter and dynamic error smaller; and in the stable process, the main cooling load in the CSTR is shouldered by the jacket cooler, more cooling efficient and lower consumption of cooling water. The dual control solution takes advantage of coil cooling and jacket cooling respectively, so that both dynamic and static characteristic of the CSTR temperature control get more ideal. Finally, the advantage of the CSTR temperature dual control is verified for control precision and dynamic response, and energy-saving and consumption reducing by the semi-physical simulation. The dual control systems solution can also be applied to other production equipment or system with the similar structure features.%连续搅拌釜式化学反应器(CSTR)是重要的化工设备.对蛇管与夹套双冷却CSTR单回路温度控制方案只利用一种操纵变量,无法兼顾动态性能与静态性能的不足进行了深入分析后,提出了CSTR温度双重控制系统方案.通过双重系统的协调控制,在温度出现偏差时由蛇管冷却器快速消除温度偏差,使温度迅速返回设定值;然后由冷却效率高的夹套冷却器逐步取代蛇管冷却器所承担的冷却负荷变化——即在动态过程,由动态性

  1. A Method for Flow Pattern Design of Axial Flow Turbine Stage%轴流透平级的最佳流型设计方法

    Institute of Scientific and Technical Information of China (English)

    辛喆; 邹滋祥

    2001-01-01

    A full mathematical model of optimal flow pattern design withengineering constraints was put forward,based on modern optimal control theory.An optimal flow pattern design was presented for optimizing meridional channel of axial flow turbine.According to integral optimization of turbine stages,a full physical model and mathematical expression were put forward for proposition of optimal flow pattern,including all performance parameters in turbine stages.This problem was further recast into a typical form control to maximize specific performance index such as work or efficiency of stage with given initial state,fixed terminal condition and constraints for part of state terminal variables.The program was also worked out according penalty function method and conjugate gradient method.The optimal distribution of C1ur1(r1) was obtained according to constraint conditions and maximized objective function.%把近代最优控制论方法引入轴流透平叶片的设计,在优化的轴流透平子午通道内,建立包括透平级内所有性能参量的最优流型命题的完整的物理模型及其数学表达式,并归化为一个在给定初始状态、自变量终端固定、部分状态变量终端受有约束的条件下,使级的某一性能指标(如级的功率)达到最优的最优控制问题,应用“代价函数法”及“共轭梯度法”编制计算程序,计算得到符合给定约束条件、并使目标函数取极值的最优环量分布,结果是令人满意的。

  2. Improving flow patterns and spillage characteristics of a box-type commercial kitchen hood.

    Science.gov (United States)

    Huang, Rong Fung; Chen, Jia-Kun; Han, Meng-Ji; Priyambodo, Yusuf

    2014-01-01

    A conventional box-type commercial kitchen hood and its improved version (termed the "IQV commercial kitchen hood") were studied using the laser-assisted smoke flow visualization technique and tracer-gas (sulfur hexafluoride) detection methods. The laser-assisted smoke flow visualization technique qualitatively revealed the flow field of the hood and the areas apt for leakages of hood containment. The tracer-gas concentration detection method measured the quantitative leakage levels of the hood containment. The oil mists that were generated in the conventional box-type commercial kitchen hood leaked significantly into the environment from the areas near the front edges of ceiling and side walls. Around these areas, the boundary-layer separation occurred, inducing highly unsteady and turbulent recirculating flow, and leading to spillages of hood containment due to inappropriate aerodynamic design at the front edges of the ceiling and side walls. The tracer-gas concentration measurements on the conventional box-type commercial kitchen hood showed that the sulfur hexafluoride concentrations detected at the hood face attained very large values on an order of magnitude about 10(3)-10(4) ppb. By combining the backward-offset narrow suction slot, deflection plates, and quarter-circular arcs at the hood entrance, the IQV commercial kitchen hood presented a flow field containing four backward-inclined cyclone flow structures. The oil mists generated by cooking were coherently confined in these upward-rising cyclone flow structures and finally exhausted through the narrow suction slot. The tracer-gas concentration measurements on the IQV commercial kitchen hood showed that the order of magnitude of the sulfur hexafluoride concentrations detected at the hood face is negligibly small--only about 10(0) ppb across the whole hood face.

  3. Cerebral Blood Flow, Heart Rate, and Blood Pressure Patterns during the Tilt Test in Common Orthostatic Syndromes

    Directory of Open Access Journals (Sweden)

    Peter Novak

    2016-01-01

    Full Text Available Objective. The head-up tilt test is widely used for evaluation of orthostatic intolerance. Although orthostatic symptoms usually reflect cerebral hypoperfusion, the cerebral blood flow velocity (CBFv profile in orthostatic syndromes is not well described. This study evaluated CBFv and cardiovascular patterns associated with the tilt test in common orthostatic syndromes. Methods. This retrospective study analyzed the tilt test of patients with history of orthostatic intolerance. The following signals were recorded: ECG, blood pressure, CBFv using transcranial Doppler, respiratory signals, and end tidal CO2. Results. Data from 744 patients were analyzed. Characteristic pattern associated with a particular orthostatic syndrome can be grouped into abnormalities predominantly affecting blood pressure (orthostatic hypotension, orthostatic hypertension syndrome, vasomotor oscillations, and neurally mediated syncope—cardioinhibitory, vasodepressor, and mixed, cerebral blood flow (orthostatic hypoperfusion syndrome, primary cerebral autoregulatory failure, and heart rate (tachycardia syndromes: postural tachycardia syndrome, paroxysmal sinus tachycardia, and inappropriate sinus tachycardia. Psychogenic pseudosyncope is associated with stable CBFv. Conclusions. The tilt test is useful add-on in diagnosis of several orthostatic syndromes. However diagnostic criteria for several syndromes had to be modified to allow unambiguous pattern classification. CBFv monitoring in addition to blood pressure and heart rate may increase diagnostic yield of the tilt test.

  4. Cerebral Blood Flow, Heart Rate, and Blood Pressure Patterns during the Tilt Test in Common Orthostatic Syndromes

    Science.gov (United States)

    2016-01-01

    Objective. The head-up tilt test is widely used for evaluation of orthostatic intolerance. Although orthostatic symptoms usually reflect cerebral hypoperfusion, the cerebral blood flow velocity (CBFv) profile in orthostatic syndromes is not well described. This study evaluated CBFv and cardiovascular patterns associated with the tilt test in common orthostatic syndromes. Methods. This retrospective study analyzed the tilt test of patients with history of orthostatic intolerance. The following signals were recorded: ECG, blood pressure, CBFv using transcranial Doppler, respiratory signals, and end tidal CO2. Results. Data from 744 patients were analyzed. Characteristic pattern associated with a particular orthostatic syndrome can be grouped into abnormalities predominantly affecting blood pressure (orthostatic hypotension, orthostatic hypertension syndrome, vasomotor oscillations, and neurally mediated syncope—cardioinhibitory, vasodepressor, and mixed), cerebral blood flow (orthostatic hypoperfusion syndrome, primary cerebral autoregulatory failure), and heart rate (tachycardia syndromes: postural tachycardia syndrome, paroxysmal sinus tachycardia, and inappropriate sinus tachycardia). Psychogenic pseudosyncope is associated with stable CBFv. Conclusions. The tilt test is useful add-on in diagnosis of several orthostatic syndromes. However diagnostic criteria for several syndromes had to be modified to allow unambiguous pattern classification. CBFv monitoring in addition to blood pressure and heart rate may increase diagnostic yield of the tilt test. PMID:27525257

  5. A Single Cell Extraction Chip Using Vibration-Induced Whirling Flow and a Thermo-Responsive Gel Pattern

    Directory of Open Access Journals (Sweden)

    Takeshi Hayakawa

    2014-09-01

    Full Text Available We propose a single cell extraction chip with an open structure, which utilizes vibration-induced whirling flow and a single cell catcher. By applying a circular vibration to a micropillar array spiral pattern, a whirling flow is induced around the micropillars, and target cells are transported towards the single cell catcher placed at the center of the spiral. The single cell catcher is composed of a single-cell-sized hole pattern of thermo-responsive gel. The gel swells at low temperatures (≲32 ◦C and shrinks at high temperatures (≳32 ◦C, therefore, its volume expansion can be controlled by an integrated microheater. When the microheater is turned on, a single cell is trapped by the hole pattern of the single cell catcher. Then, when the microheater is turned off, the single cell catcher is cooled by the ambient temperature. The gel swells at this temperature, and the hole closes to catch the single cell. The caught cell can then be released into culture wells on a microtiter plate by heating the gel again. We conducted single cell extraction with the proposed chip and achieved a 60% success rate, of which 61% cells yielded live cells.

  6. Period-doubling and chaotic oscillations in the ferroin-catalyzed Belousov-Zhabotinsky reaction in a CSTR

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The ferroin-catalyzed Belousov-Zhabotinsky(BZ) reaction,the oxidation of malonic acid by acidic bromate,is the most commonly investigated chemical system for understanding spatial pattern forma-tion. Various oscillatory behaviors were found from such as mixed-mode and simple period-doubling oscillations and chaos on both Pt electrode and Br-ISE at high flow rates to mixed-mode oscillations on Br-ISE only at low flow rates. The complex dynamic behaviors were qualitatively reproduced with a two-cycle coupling model proposed initially by Gy?rgyi and Field. This investigation offered a proper medium for studying pattern formation under complex temporal dynamics. In addition,it also shows that complex oscillations and chaos in the BZ reaction can be extended to other bromate-driven nonlinear reaction systems with different metal catalysts.

  7. Period-doubling and chaotic oscillations the ferroin-catalyzed Belousov-Zhabotinsky reaction in a CSTR

    Institute of Scientific and Technical Information of China (English)

    ZONG ChunYan; GAO QingYu; WANG YuMei; FENG JiaMin; MAO ShanCheng; ZHANG Lu

    2007-01-01

    The ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction, the oxidation of malonic acid by acidic bromate, is the most commonly investigated chemical system for understanding spatial pattern formation. Various oscillatory behaviors were found from such as mixed-mode and simple period-doubling oscillations and chaos on both Pt electrode and Br-ISE at high flow rates to mixed-mode oscillations on Br-ISE only at Iow flow rates. The complex dynamic behaviors were qualitatively reproduced with a two-cycle coupling model proposed initially by Gy(o)rgyi and Field. This investigation offered a proper medium for studying pattern formation under complex temporal dynamics. In addition, it also shows that complex oscillations and chaos in the BZ reaction can be extended to other bromate-driven nonlinear reaction systems with different metal catalysts.

  8. Observation of the CSF pulsatile flow in the aqueduct using cine MRI with presaturation bolus tracking, 3; The pathophysiological significance of the pulsatile flow patterns in adult patients with ventriculomegaly

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Satoshi (Tokyo Medical Coll. (Japan))

    1992-06-01

    The to-and-fro motion patterns of the CSF flow in the aqueduct in ten normal adults, ten patients with secondary normal-pressure hydrocephalus (NPH), and fourteen patients with idiopathic ventriculomegaly were analyzed using cine MRI with presaturation bolus tracking. The to-and-fro motion patterns of the CSF flow in the aqueduct were thus classified into four types according to their maximum velocity and the relative time duration of their flow in the rostral and caudal directions. The correlation between the clinical symptoms, the CT findings, the RI-cisternography findings, the results of the ICP monitorings, and the CSF pulsatile-flow patterns were then analyzed. In secondary NPH disclosing frequent B waves on ICP monitoring, the maximum velocity of the CSF flow in the aqueduct was over 15 mm/sec, and the duration of the CSF flow was longer in the caudal direction than in the rostral direction. Furthermore, the faster the maximum velocity of the CSF flow, the larger the ventricular size on CT and the more severe the CSF malabsorption on cisternography. In idiopathic ventriculomegaly, only two cases demonstrated the same CSF flow pattern as was shown in secondary NPH; the other cases demonstrated other CSF flow patterns, which were considered to indicate hydrocephalus ex vacuo or arrested hydrocephalus. The CSF pulsatile-flow pattern was assumed to change according to the degree of the CSF circulatory disorder, its compensatory process, and the plasticity of the brain. The investigation of the CSF pulsatile flow gives important information for the evaluation of various hydrocephalic conditions. (author).

  9. Local Three-dimensional Flow and Sediment Patterns as an Evidence of Pool-riffle Self-maintenance

    Science.gov (United States)

    Rodriguez, J. F.; Vahidi, E.; Bayat, E.; Saco, P. M.; de Almeida, G. A. M.

    2015-12-01

    For decades pool-riffle morphodynamics has been described based on the cross- sectional averaged flow characteristics, using episodic shifts in higher shear stress or velocities from the riffles to the pools (i.e. reversal conditions) as an indication of the long term self-maintenance of the structures. Recently more attention has been paid to three-dimensional flow features and sediment transport characteristics, but this has been done in a compartmentalised way, with studies either focusing on one or the other aspect. In this study, we present for the first time a three-dimensional analysis of sediment transport processes as an indication of self-maintenance mechanisms due to erosion and aggradation in pools and riffles. We do that by first reconstructing from experimental data the 3-D flow patterns in a typical pool-riffle sequence and computing bed shear stress distribution and near-bed streamlines for low and high flow conditions. We then use these 3-D features to complement a one-year dataset from an unsteady fractional sediment transport and bed evolution model applied to an existing stream. Local instantaneous bedload transport is obtained using the bed shear stress distribution corresponding to the flow condition (low or high) and assumed to follow the streamlines for that flow condition (low or high). Streamlines laterally contract and expand on pools and riffles, respectively, but in a different way during low and high flow condition. We apply the streamtube concept to compute instantaneous local rates of sediment transport in pools and contiguous downstream riffles and compute reversal conditions and identify self-maintenance episodes. Comparison with reversal episodes identified using cross- sectional average values reveal that when considering the 3-D effects stronger reversal episodes were detected, but the actual number of episodes increased only slightly (8%). Most reversal episodes occurred in the streamtubes that originated near the centre of the

  10. Indoor Airflow Patterns, Dispersion of Human Exhalation Flow and Risk of Airborne Cross-infection between People in a Room

    DEFF Research Database (Denmark)

    Olmedo, Inés

    In recent years, an interest in understanding the mechanisms of cross-infection between people in the same room has increased significantly. The SARS (Severe Acute Respiratory Syndrome) outbreak occurred in Asia in 2003 reopened the study of the airborne disease transmission as one of the most...... in the air. These tiny particles or droplet nuclei can follow the air flow pattern in the room and produce high contaminant concentration in different areas of the indoor environment. This fact can provoke a high exposure to exhaled contaminants and a risk of cross-infection to a susceptible person situated...... in the same room. Abundant evidence shows that the air flow distribution systems play a crucial role in the dispersion of these human exhaled contaminants. However, there are many parameters that influence the cross-infection risk between people situated close to each other in a ventilated room, such as...

  11. Indoor Airflow Patterns, Dispersion of Human Exhalation Flow and Risk of Airborne Cross-Infection between People in a Room

    DEFF Research Database (Denmark)

    Olmedo, Inés

    In recent years, an interest in understanding the mechanisms of cross-infection between people in the same room has increased significantly. The SARS (Severe Acute Respiratory Syndrome) outbreak occurred in Asia in 2003 reopened the study of the airborne disease transmission as one of the most...... in the air. These tiny particles or droplet nuclei can follow the air flow pattern in the room and produce high contaminant concentration in different areas of the indoor environment. This fact can provoke a high exposure to exhaled contaminants and a risk of cross-infection to a susceptible person situated...... in the same room. Abundant evidence shows that the air flow distribution systems play a crucial role in the dispersion of these human exhaled contaminants. However, there are many parameters that influence the cross-infection risk between people situated close to each other in a ventilated room, such as...

  12. Availability of MCNP & MATLAB for reconstructing the water-vapor two-phase flow pattern in neutron radiography

    Institute of Scientific and Technical Information of China (English)

    FENG Qixi; FENG Quanke; TAKESHI Kawai

    2008-01-01

    The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008. In this paper, we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the tube were obtained using the MCNP code without influence of γ-ray and electronic-noise. The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated. The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI. The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques. And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI.

  13. PATTERNS UTILIZED IN THE SIMULATION OF UNDERGROUND WATER FLOW AND THE TRANSPORTATION OF POLLUTANTS IN THE BAHLUI DRAINAGE BASIN

    Directory of Open Access Journals (Sweden)

    Ionut Minea

    2012-03-01

    Full Text Available ABSTRACT. – Patterns utilized in the simulation of underground water flow and the transportation of pollutants in the Bahlui drainage basin. In the actual context of accelerate economic development, the excessive exploatation of water resources from the underground and the contamination of these with different water pollutants has become a major problem which has enetered the attention of many researchers. For the evaluation of an underground water flow and pollutants transport sistem we have chosen the package of programs MODFLOW which includes a whole series of applications,such as MOC3D, MT3D, MT3DMS, PEST, UCODE, PMPATH, which allow simulations and multiple recalibrations of the capacity of recharging of the aquifers, the flowing of the water towards wells and drillings the transport of a pollutant agent in the underground or the evaluation of the exchange of water between the hidrographic network and aquifers. The sistem targets both the evaluation of the modelation of the underground flowing and the simulation of a punctual polluation of the canvas of groundwater scenery, in the meadow of the river Bahlui, west from Letcani village.

  14. Generation of three-dimensional patterns through wave interaction in a model of free surface swirling flow

    Energy Technology Data Exchange (ETDEWEB)

    Fabre, D; Mougel, J, E-mail: david.fabre@imft.fr [Institut de Mécanique des Fluides de Toulouse (IMFT), University of Toulouse (France)

    2014-12-01

    The free surface flow in a cylindrical tank over a rotating bottom is known to support spectacular three-dimensional patterns, including deformation of the inner free surface into the shape of rotating polygons and sloshing behavior of the upper free surface (e.g. Iga et al 2014 Fluid Dyn. Res. 46 031409). Through a stability analysis of a simplified model of this flow, we show that such patterns can be explained as a resonance mechanism involving different families of waves. The approach extends a previous work (Tophøj et al 2013 Phys. Rev. Lett. 110 194502) which explained the rotating polygons as an interaction between gravity waves and centrifugal waves, under the assumption that the base flow can be modeled as a potential vortex. We show that this previous model is justified for strong rotation rates (Dry-Potential case), and that for weaker rotations it can be improved by introducing an inner vortex core in solid-body rotation, which either extends to the center of the plate (Wet case) or surrounds a dry central region (Dry-Composite case). The study of this improved model predicts two new kinds of instabilities. The first occurs at low rotations (Wet case) and results from an interaction between gravity waves and the Kelvin–Kirchhoff wave (namely, oscillation of the boundary of the vortex core). This instability is proposed to be at the origin of the sloshing phenomenon. The second new instability occurs, for moderate rotations, (Dry-Composite case) as an interaction between gravity waves and a ‘Kelvin-Centrifugal’ wave characterized by deformation of the inner surface and the vortex core boundary in opposite directions. This instability exists for all azimuthal wave numbers starting from m = 1, this case corresponding to a ‘monogon’ pattern. (paper)

  15. Numerical study of junction-angle effects on flow pattern in a river ...

    African Journals Online (AJOL)

    2016-01-01

    Jan 1, 2016 ... This complexity is not only because of their turbulence and intense ... The use of numerical models for simulating the flow in river junctions has ..... longitudinal velocity profiles in different sections of the main channel is shown ...

  16. Characterization of fracture patterns and hygric properties for moisture flow modelling in cracked concrete

    DEFF Research Database (Denmark)

    Rouchier, Simon; Janssen, Hans; Rode, Carsten

    2012-01-01

    Several years after their installation, building materials such as concrete present signs of ageing in the form of fractures covering a wide range of sizes, from microscopic to macroscopic cracks. All sizes of fractures can have a strong influence on heat and moisture flow in the building envelop...

  17. Effect of advanced and delayed rotation on the dominant flow pattern and its temporal evolution

    Science.gov (United States)

    Uksul, Esra; Krishna, Swathi; Mulleners, Karen

    2015-11-01

    During a flapping cycle of an insect, complex time dependent flows are produced as the wing reciprocates, producing a maximum lift at the stroke reversals. By flipping the wing rapidly at the end of each stroke, the insect modulates the flow around the wing and hence the aerodynamic forces necessary to hover. The duration and starting point of the flip play an important role in determining the amount of lift produced. To understand and tailor the effect of wing kinematics on the aerodynamic performance we focussed on the vortex dynamics of the flow field. Phase-averaged data from particle image velocimetry was used to evaluate the flow features inherent to changes in rotation during a stroke of a flat plate, which is modelled based on hoverfly characteristics. The period of rotation is one-third of the total time period. A +10% phase shift is used for delayed rotation, a -10% phase shift for advanced rotation. Vortex detection methods like the λ2 and Γ2 criteria are used to determine the effect of a delay or early rotation on the trajectories, size, shape and location of the prominent vortical structures. Proper orthogonal decomposition is used to study the influence of the phase-shifts on the dominant mode structure and the related time-scales.

  18. Patterns of gene flow between crop and wild carrot, Daucus carota (Apiaceae) in the United States

    Science.gov (United States)

    Studies of gene flow between crops and their wild relatives have implications for both management practices for farming and breeding as well as understanding the risk of transgene escape. These types of studies may also yield insight into population dynamics and the evolutionary consequences of gene...

  19. Cognitive profiles and regional cerebral blood flow patterns in dementia of the Alzheimer type

    DEFF Research Database (Denmark)

    Waldemar, G; Bruhn, P; Schmidt, E

    1994-01-01

    Individual cognitive profiles and correlations between cognitive functions and regional cerebral blood flow (rCBF) were analyzed in 20 consecutive patients with a clinical diagnosis of probable Alzheimer's disease (AD). CBF was measured with high resolution single photon emission computed...

  20. Air flow patterns and noise analysis inside high speed angular contact ball bearings

    Institute of Scientific and Technical Information of China (English)

    翟强; 闫柯; 张优云; 朱永生; 王亚泰

    2015-01-01

    The vortex formed around the rolling ball and the high pressure region formed around the ball−raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil−air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil−air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.

  1. Experimental study of swirl flow patterns in Gas Conditioning Tower at various entry conditions

    DEFF Research Database (Denmark)

    Jinov, Andrei A.; Larsen, Poul Scheel

    1999-01-01

    In a gas conditioning tower hot flue gas with relatively high dust loads is cooled by injecting water spray near the top. For satisfactory operation wet particles should be kept off walls and all water should have evaporated to yield a uniformly cooled flow before it reaches the bottom of the tower...

  2. Wake flow pattern modified by small control cylinders at low Reynolds number

    Science.gov (United States)

    Kuo, C.-H.; Chiou, L.-C.; Chen, C.-C.

    2007-08-01

    Passive wake control behind a circular cylinder in uniform flow is studied by numerical simulation for ReD ranging from 80 to 300. Two small control cylinders, with diameter d/D=1/8, are placed at x/D=0.5 and y/D=±0.6. Unlike the 1990 results of Strykowski and Sreenivasan, in the present study, the vortex street behind the main cylinder still exists but the fluctuating lift and the form drag on the main cylinder reduces significantly and monotonously as the Reynolds number increases from 80 to 300. Obstruction of the control cylinders to the incoming flow deflects part of the fluid to pass through the gap between the main and control cylinders, forming two symmetric streams. These streams not only eliminate the flow separation along the rear surface of the main cylinder, they also merge toward the wake centerline to create an advancing momentum in the immediate near-wake region. These two effects significantly reduce the wake width behind the main cylinder and lead to monotonous decrease of the form drag as the Reynolds number increases. As the Reynolds number gets higher, a large amount of the downstream advancing momentum significantly delays the vortex formation farther downstream, leading to a more symmetric flow structure in the near-wake region of the main cylinder. As the Reynolds number increases from 80 to 300, both increasing symmetry of the flow structure in the near-wake and significant delay of the vortex formation are the main reasons for the fluctuating lift to decrease monotonously.

  3. Explaining spatial patterns of sap flow: day-to-day shifts in relevance of site- and tree-specific controls

    Science.gov (United States)

    Hassler, Sibylle K.; Weiler, Markus; Blume, Theresa

    2015-04-01

    Transpiration is a key process in the hydrological cycle and a sound understanding and quantification of transpiration is essential for management decisions and for hydrological and climatological modelling. To assess transpiration at the tree scale sap flow velocity is commonly measured. Besides atmospheric conditions and soil moisture state, tree-specific characteristics such as species, size or social status control sap flow of individual trees. Within forest stands, properties such as species composition, basal area or stem number also affect sap flow via competition or facilitation mechanisms. Finally, sap flow patterns might also be influenced by landscape-scale characteristics such as geology, slope position or aspect because they affect water and energy availability; however, so far little is known about these larger-scale controls. We studied the relative importance of various tree- and site-specific characteristics with linear statistical models for daily sap velocity observations on 38 trees at 12 locations in mixed beech and oak forests in a catchment in Luxemburg. The temporal variation of the predictors' importance for sap velocity patterns was then related to hydro-meteorological conditions. Results indicate that a combination of tree- and site-specific controls influence sap velocity patterns, namely tree species, tree diameter, stand basal area, geology and aspect. The temporal dynamics of these controls are related to hydro-meteorological conditions, with tree-specific controls dominating when the atmospheric gradient is strong, i.e. the vapour pressure deficit is large, leading to higher sap velocities, whereas landscape-scale site characteristics are more important during weak atmospheric gradients. The importance of individual predictors also varies between spring and summer, probably due to different soil moisture and atmospheric conditions of the two periods. We conclude that both tree- and site-specific characteristics control sap velocity

  4. Improving double patterning flow by analyzing the diffractive orders in the pupil plane

    Science.gov (United States)

    Zeggaoui, N.; Farys, V.; Besacier, M.; Li, Q.; Yesilada, E.; Trouiller, Y.

    2011-04-01

    To print sub 22nm node features, current lithography technology faces some tool limitations. One possible solution to overcome these problems is to use the double patterning technique (DPT). The principle of the double patterning technique is pitch splitting where two adjacent features must be assigned opposite masks (colors) corresponding to different exposures if their pitch is less than a predefined minimum coloring pitch. However, certain design orientations for which pattern features separated by more than the minimum coloring pitch cannot be imaged with either of the two exposures. In these directions, the contrast and the process window are degraded because constructive interferences between diffractive orders in the pupil plane are not sufficient. The 22nm and 16nm nodes require the use of very coherent sources that will be generated using SMO (source mask cooptimization). Such pixelized sources while helpful in improving the contrast for selected configurations, can lead to degrade it for configurations which have not been counted for during the SMO process. Therefore, we analyze the diffractive orders interactions in the pupil plane in order to detect these limited orientations in the design and thus propose a new double patterning decomposition algorithm to enlarge the process window and the contrast of each mask.

  5. Three-dimensional flow patterns in the feto-placental vasculature system of the mouse placenta.

    Science.gov (United States)

    Shannon, Alexander T; Mirbod, Parisa

    2017-05-01

    In this study, three-dimensional (3D) blood flow of the feto-placental vasculature system of the mouse placenta was investigated using computational fluid dynamics (CFD) methods and finite element analysis. Micro-computerized tomography (micro-CT) images were used to acquire the 3D geometry of the feto-placental vasculature system, and image-processing software has been used to calculate the 3D morphology of the placenta. The flow was analyzed numerically and compared to the experimental data received from the same model. The numerical and experimental results agree well. Experimentally measured time dependent blood velocity data, available in the literature, was used as the inlet boundary condition to represent the fetal blood pulsatile flow. Velocity profiles and pressure distributions are investigated during different phases of the unsteady flow. The results clearly illustrate the important role of the vasculature structure (e.g., diameter and curvature) in the fetal hemodynamics, which to our knowledge has not been examined previously. The data also show that, at each bifurcation, the blood flow velocity decreases significantly in the transition from the parent vessel (i.e., umbilical artery) to the daughter vessels because of the higher total cross-sectional area of the daughter vessels compared to the parent vessel. It can also be observed that pressure drop at the umbilical artery and pressure drop across the arterial trees obtained in this study agree well with the physiological data reported in the literature. Moreover, the velocity profiles after each bifurcation are symmetric. Finally, from the results no secondary flow has been observed in the vasculature system. This study provides a foundation in understanding and modeling the complex structure of the feto-placental vasculature system and serves as a first step towards developing new concepts for computational analysis of the feto-placental vasculature systems of both human and mouse to better

  6. Experimental determination of coolant flow pattern in hot and cold pools of PFBR using a large scale model

    Energy Technology Data Exchange (ETDEWEB)

    Indranil Banerjee; Rajesh, K.; AnandaRaj, M.; Venkata Ramanan, J.; Gopal, C.A.; Padmakumar, G.; Prakash, V.; Vaidyanathan, G. [Indira Gandhi Center for Atomic Research, Kalpakkam, 603102 (India)

    2005-07-01

    Full text of publication follows: The construction of Prototype Fast Breeder Reactor (PFBR) to generate 500 MWe has commenced at Kalpakkam, India. PFBR is a liquid sodium cooled pool type reactor with two secondary loops. The primary sodium pool is divided into hot pool and cold pool by means of Inner vessel. Cold sodium at 670 K is pumped through the core subassemblies and after absorbing the fission heat in the core, the sodium comes out and mixes with the hot pool at 820 K. This hot sodium exchanges heat with secondary sodium in Intermediate Heat Exchangers (IHX) which in turn transfers the heat to water in the steam generator leading to production of superheated steam to generate power. All the components like Control Plug (CP), IHX, Decay Heat Exchangers (DHX), Pump etc., are immersed in the primary sodium pool. The presence of these components influence the flow and velocity patterns of the coolant, in the hot and cold pools. The coolant behaviour in the pool is an indicator of the temperature pattern in the pool and the mechanical and thermal stresses induced on the immersed structures during transients is of significance for the safe operation of the reactor, designed for a life span of 40 years. Hence it is essential to understand the pattern of coolant flow and velocity patterns in hot and cold pools, particularly near IHX and Control plug. A 1:4 scale down model in stainless steel is constructed, simulating all the internal structures of the PFBR primary circuit for investigating the various parameters experimentally in water, to enhance the confidence in design of the primary system. The velocity distribution in the hot pool and cold pool at different regions, around the control plug, around the IHX inlet window were studied experimentally. As the coolant flow path is mainly influenced by the gravity force and inertia force, the study is conducted using Froude similitude. The magnitude of the velocity of the fluid at different points on the selected

  7. Kinetic modelling of nitrogen and organics removal in vertical and horizontal flow wetlands.

    Science.gov (United States)

    Saeed, Tanveer; Sun, Guangzhi

    2011-05-01

    This paper provides a comparative evaluation of the kinetic models that were developed to describe the biodegradation of nitrogen and organics removal in wetland systems. Reaction kinetics that were considered in the model development included first order kinetics, Monod and multiple Monod kinetics; these kinetics were combined with continuous-stirred tank reactor (CSTR) or plug flow pattern to produce equations to link inlet and outlet concentrations of each key pollutants across a single wetland. Using three statistical parameters, a critical evaluation of five potential models was made for vertical and horizontal flow wetlands. The results recommended the models that were developed based on Monod models, for predicting the removal of nitrogen and organics in a vertical and horizontal flow wetland system. No clear correlation was observed between influent BOD/COD values and kinetic coefficients of BOD(5) in VF and HF wetlands, illustrating that the removal of biodegradable organics was insensitive to the nature of organic matter. Higher effluent COD/TN values coincided with greater denitrification kinetic coefficients, signifying the dependency of denitrification on the availability of COD in VF wetland systems. In contrast, the trend was opposite in HF wetlands, indicating that availability of NO(3)-N was the main limiting step for nitrogen removal. Overall, the results suggested the possible application of the developed alternative predictive models, for understanding the complex biodegradation routes of nitrogen and organics removal in VF and HF wetland systems.

  8. Effect of heating conditions on flow patterns during the seeding stage of Kyropoulos sapphire crystal growth

    Science.gov (United States)

    Timofeev, Vladimir V.; Kalaev, Vladimir V.; Ivanov, Vadim G.

    2016-07-01

    We apply numerical simulation to understand the effect of heating conditions on melt convection in an industrial Ky furnace. The direct numerical simulation (DNS) approach was used to investigate the features of melt flow during the seeding stage. Two different cases of Kyropoulos furnace hot zone design were studied numerically, and results were compared with experimental data to understand the effect of modifications on melt convection.

  9. Enhanced efficiency of feeding and mixing due to chaotic flow patterns around choanoflagellates.

    Science.gov (United States)

    Orme, B. A. A.; Otto, S. R.; Blake, J. R.

    2000-11-01

    The motion of particles and feeding currents created by micro-organisms due to a flagellum beating are considered. The calculations are pertinent to a range of sessile organisms, but we concentrate on a particular organism, namely Salpingoeca Amphoridium (SA) (a choanoflagellate); due to the availability of experimental data, Pettitt (2000). These flow fields are characterised as having very small Reynolds numbers, which implies that viscous forces dominate over inertial ones consistent with the Stokes flow limit. The flow generated by the flagella is modelled via consideration of a point force known as a stokeslet. The interaction between the boundary to which the organism is attached and its flagellum leads to toroidal eddies, which serve to transport particles towards the micro-organism; promoting filtering of nutrients by the microvilli which constitute the cell's collar (the filtering mechanism in SA). It is our conjecture that the interaction of multiple toroidal eddies will lead to chaotic advection and hence enhance the domain of feeding for these organisms. The degree of mixing in the region around SA is investigated using chaotic and statistical measures to study the influence the flagellum has on the surrounding fluid. Three-dimensional particle paths around such an organism are considered with the aim of showing the plane within which the stokeslets are situated is an attractor.

  10. Detection of particle flow patterns in tumor by directional spatial frequency analysis

    Science.gov (United States)

    Russell, Stewart; Camara, Hawa; Shi, Lingyan; Hoopes, P. Jack; Kaufman, Peter; Pogue, Brian; Alfano, Robert

    2016-04-01

    Drug delivery to tumors is well known to be chaotic and limited, partly from dysfunctional vasculature, but also because of microscopic regional variations in composition. Modeling the of transport of nanoparticle therapeutics, therefore must include not only a description of vascular permeability, but also of the movement of the drug as suspended in tumor interstitial fluid (TIF) once it leaves the blood vessel. Understanding of this area is limited because we currently lack the tools and analytical methods to characterize it. We have previously shown that directional anisotropy of drug delivery can be detected using Directional Fourier Spatial Frequency (DFSF) Analysis. Here we extend this approach to generate flow line maps of nanoparticle transport in TIF relative to tumor ultrastructure, and show that features of tumor spatial heterogeneity can be identified that are directly related to local flow isometries. The identification of these regions of limited flow may be used as a metric for determining response to therapy, or for the optimization of adjuvant therapies such as radiation pre-treatment, or enzymatic degradation.

  11. Inferred vs realized patterns of gene flow: an analysis of population structure in the Andros Island Rock Iguana.

    Directory of Open Access Journals (Sweden)

    Giuliano Colosimo

    Full Text Available Ecological data, the primary source of information on patterns and rates of migration, can be integrated with genetic data to more accurately describe the realized connectivity between geographically isolated demes. In this paper we implement this approach and discuss its implications for managing populations of the endangered Andros Island Rock Iguana, Cyclura cychlura cychlura. This iguana is endemic to Andros, a highly fragmented landmass of large islands and smaller cays. Field observations suggest that geographically isolated demes were panmictic due to high, inferred rates of gene flow. We expand on these observations using 16 polymorphic microsatellites to investigate the genetic structure and rates of gene flow from 188 Andros Iguanas collected across 23 island sites. Bayesian clustering of specimens assigned individuals to three distinct genotypic clusters. An analysis of molecular variance (AMOVA indicates that allele frequency differences are responsible for a significant portion of the genetic variance across the three defined clusters (Fst =  0.117, p<<0.01. These clusters are associated with larger islands and satellite cays isolated by broad water channels with strong currents. These findings imply that broad water channels present greater obstacles to gene flow than was inferred from field observation alone. Additionally, rates of gene flow were indirectly estimated using BAYESASS 3.0. The proportion of individuals originating from within each identified cluster varied from 94.5 to 98.7%, providing further support for local isolation. Our assessment reveals a major disparity between inferred and realized gene flow. We discuss our results in a conservation perspective for species inhabiting highly fragmented landscapes.

  12. Quantitative assessment of harmonic power doppler myocardial perfusion imaging with intravenous levovist™ in patients with myocardial infarction: comparison with myocardial viability evaluated by coronary flow reserve and coronary flow pattern of infarct-related artery

    Directory of Open Access Journals (Sweden)

    Nagai Kunihiko

    2005-08-01

    Full Text Available Abstract Background Myocardial contrast echocardiography and coronary flow velocity pattern with a rapid diastolic deceleration time after percutaneous coronary intervention has been reported to be useful in assessing microvascular damage in patients with acute myocardial infarction. Aim To evaluate myocardial contrast echocardiography with harmonic power Doppler imaging, coronary flow velocity reserve and coronary artery flow pattern in predicting functional recovery by using transthoracic echocardiography. Methods Thirty patients with anterior acute myocardial infarction underwent myocardial contrast echocardiography at rest and during hyperemia and were quantitatively analyzed by the peak color pixel intensity ratio of the risk area to the control area (PIR. Coronary flow pattern was measured using transthoracic echocardiography in the distal portion of left anterior descending artery within 24 hours after recanalization and we assessed deceleration time of diastolic flow velocity. Coronary flow velocity reserve was calculated two weeks after acute myocardial infarction. Left ventricular end-diastolic volumes and ejection fraction by angiography were computed. Results Pts were divided into 2 groups according to the deceleration time of coronary artery flow pattern (Group A; 20 pts with deceleration time ≧ 600 msec, Group B; 10 pts with deceleration time Conclusion The preserved microvasculature detecting by myocardial contrast echocardiography and coronary flow velocity reserve is related to functional recovery after acute myocardial infarction.

  13. An experimental study of the size effect on adiabatic gas-liquid two-phase flow patterns and void fraction in microchannels

    Science.gov (United States)

    Xiong, Renqiang; Chung, J. N.

    2007-03-01

    Adiabatic gas-liquid flow patterns and void fractions in microchannels were experimentally investigated. Using nitrogen and water, experiments were conducted in rectangular microchannels with hydraulic diameters of 0.209mm, 0.412mm and 0.622mm, respectively. Gas and liquid superficial velocities were varied from 0.06-72.3m/s and 0.02-7.13m/s, respectively. The main objective is focused on the effects of microscale channel sizes on the flow regime map and void fraction. The instability of flow patterns was observed. Four groups of flow patterns including bubbly slug flow, slug-ring flow, dispersed-churn flow, and annular flow were observed in microchannels of 0.412mm and, 0.622mm. In the microchannel of 0.209mm, the bubbly slug flow became the slug flow and the dispersed-churn flow disappeared. The current flow regime maps showed the transition lines shifted to higher gas superficial velocity due to a dominant surface tension effect as the channel size was reduced. The regime maps presented by other authors for minichannels were found to not be applicable for microchannels. Time-averaged void fractions were measured by analyzing 8000 high speed video images for each flow condition. The void fractions hold a nonlinear relationship with the homogeneous void fraction as opposed to the relatively linear trend for the minichannels. A new correlation was developed to predict the nonlinear relationship that fits most of the current experimental data and those of the 0.1mm diameter tube reported by Kawahara et al. [Int. J. Multiphase Flow 28, 1411 (2002)] within ±15%.

  14. 3D imaging of flow patterns in an internally-pumped microfluidic device: redox magnetohydrodynamics and electrochemically-generated density gradients.

    Science.gov (United States)

    Gao, Feng; Kreidermacher, Adam; Fritsch, Ingrid; Heyes, Colin D

    2013-05-07

    Redox magnetohydrodynamics (MHD) is a promising technique for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction and adjusting flow speeds and flow patterns as well as avoiding bubble formation. However, a detailed description of all the forces involved and predicting flow patterns in confined geometries is lacking. In addition to redox-MHD, density gradients caused by the redox reactions also play important roles. Flow in these devices with small fluid volumes has mainly been characterized by following microbead motion by optical microscopy either by particle tracking velocimetry (PTV) or by processing the microbead images by particle image velocimetry (PIV) software. This approach has limitations in spatial resolution and dimensionality. Here we use fluorescence correlation spectroscopy (FCS) to quantitatively and accurately measure flow speeds and patterns in the ~5-50 μm/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 μm. The 2 μm spatial resolution flow speeds map revealed detailed flow profiles during redox-MHD in which the velocity increases linearly from above the electrode and reaches a plateau across the center of the cell. By combining FCS and video-microscopy (with PTV and PIV processing approaches), we are able to quantify a vertical flow of ~10 μm/s above the electrodes as a result of density gradients caused by the redox reactions and follow convection flow patterns. Overall, combining FCS, PIV, and PTV analysis of redox-MHD is a powerful combination to more thoroughly characterize the underlying forces in these promising microfluidic devices.

  15. SIMATIC PCS7在CSTR中的设计方案及其应用%Design Scheme for SIMATIC PCS7 in CSTR and Its Application

    Institute of Scientific and Technical Information of China (English)

    张兴越; 杨国田; 陈峭; 秦宇飞

    2008-01-01

    过程工业常见的连续搅拌釜式反应系统(CSTR)其内部化学反应不稳定,直接影响生产的安全和效率,控制比较复杂.为实现对CSTR的稳定控制,介绍了应用传统控制算法而设计的针对CSTR的控制策略并通过仿真实验验证其性能.传统控制算法具有实现简单、控制性能稳定的优点,为了适应CSTR 化学反应的复杂性,本文灵活应用传统控制算法,严格控制反应物的进料时序,进而控制釜内反应的速度,实现CSTR 的安全稳定性和生产效率可控制性.同时,利用西门子新一代工业可编程控制器--SIMATIC PCS7 BOX作为控制器,在多功能过程控制仿真实验系统(MPCE-1000)上构建的CSTR仿真对象上实现稳定控制.仿真结果表明该控制策略在一定程度上能够适应CSTR 的复杂反应.

  16. Exploring the physical controls of regional patterns of flow duration curves - Part 1: Insights from statistical analyses

    Science.gov (United States)

    Cheng, L.; Yaeger, M.; Viglione, A.; Coopersmith, E.; Ye, S.; Sivapalan, M.

    2012-11-01

    The flow duration curve (FDC) is a classical method used to graphically represent the relationship between the frequency and magnitude of streamflow. In this sense it represents a compact signature of temporal runoff variability that can also be used to diagnose catchment rainfall-runoff responses, including similarity and differences between catchments. This paper is aimed at extracting regional patterns of the FDCs from observed daily flow data and elucidating the physical controls underlying these patterns, as a way to aid towards their regionalization and predictions in ungauged basins. The FDCs of total runoff (TFDC) using multi-decadal streamflow records for 197 catchments across the continental United States are separated into the FDCs of two runoff components, i.e., fast flow (FFDC) and slow flow (SFDC). In order to compactly display these regional patterns, the 3-parameter mixed gamma distribution is employed to characterize the shapes of the normalized FDCs (i.e., TFDC, FFDC and SFDC) over the entire data record. This is repeated to also characterize the between-year variability of "annual" FDCs for 8 representative catchments chosen across a climate gradient. Results show that the mixed gamma distribution can adequately capture the shapes of the FDCs and their variation between catchments and also between years. Comparison between the between-catchment and between-year variability of the FDCs revealed significant space-time symmetry. Possible relationships between the parameters of the fitted mixed gamma distribution and catchment climatic and physiographic characteristics are explored in order to decipher and point to the underlying physical controls. The baseflow index (a surrogate for the collective impact of geology, soils, topography and vegetation, as well as climate) is found to be the dominant control on the shapes of the normalized TFDC and SFDC, whereas the product of maximum daily precipitation and the fraction of non-rainy days was found to

  17. 基于MATLAB的CSTR过程仿真控制研究%Research on simulation and control of CSTR process based on MATLAB

    Institute of Scientific and Technical Information of China (English)

    方璐; 吴志刚; 陈安钢

    2016-01-01

    Continuous Stirred Tank Reactor ( CSTR) has been widely used in the production process. But in the actual production process, it will be affected by many unfavorable factors, as a result, it is not easy to achieve performance oriented control. Based on the continuous stirring reac-tor for object, using the conventional PID control, in order to achieve real-time modified model parameters, dynamic display and variable numeri-cal control curve, we design a GUI interface in this experiment which allows users to monitor CSTR control system more fluently and real-timely.%连续搅拌反应釜( CSTR)在生产过程中得到了广泛应用。因其在实际生产过程中会受到许多不利因素的影响,不易实现面向性能的控制。以连续搅拌反应釜为对象,采用常规PID控制,为了达到实时修改模型参数,动态显示控制曲线和变量数值的目的,设计了GUI人机界面,使得用户可以方便、实时地对CSTR控制系统进行监控。

  18. Anaerobic treatment of cassava stillage for hydrogen and methane production in continuously stirred tank reactor (CSTR) under high organic loading rate (OLR)

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Gang; Xie, Li; Zou, Zhonghai; Wang, Wen; Zhou, Qi [Key Laboratory of Yangtze River Water Environment, Ministry of Education (Tongji University), UNEP-Tongji, Tongji University, Siping Road No. 1239, Shanghai 200092 (China); Shim, Hojae [Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau SAR 999078 (China)

    2010-11-15

    Anaerobic hydrogen and methane production from cassava stillage in continuously stirred tank reactor (CSTR) were investigated in this study. Results showed that the heat-pretreatment of inoculum did not enhance hydrogen yield compared to raw inoculum under mesophilic condition after continuous operation. However, the hydrogen yield increased from about 14 ml H{sub 2}/gVS under mesophilic condition to 69.6 ml H{sub 2}/gVS under thermophilic condition due to the decrease of propionate concentration and inhibition of homoacetogens. Therefore, temperature was demonstrated to be more important than pretreatment of inoculum to enhance the hydrogen production. Under high organic loading rate (OLR) (>10 gVS/(L.d)), the two-phase thermophilic CSTR for hydrogen and methane production was stable with hydrogen and methane yields of 56.6 mlH{sub 2}/gVS and 249 mlCH{sub 4}/gVS. The one-phase thermophilic CSTR for methane production failed due to the accumulation of both acetate and propionate, leading to the pH lower than 6. Instead of propionate alone, the accumulations of both acetate and propionate were found to be related to the breakdown of methane reactor. (author)

  19. Linking local riverbed flow patterns and pore-water chemistry to hydrogeologic and geomorphic features across scales

    Science.gov (United States)

    Ibrahim, T. G.; Thornton, S.; Surridge, B.; Wainwright, J.

    2009-12-01

    The groundwater-surface water interface (GSI) is a critical environmental hotspot, a key area influencing the fate of carbon, nutrients and contaminants of surface and subsurface origin, and a zone of ecological importance. Policy seeking to mitigate issues relating to dissolved contaminants and to improve stream health, increasingly recognizes its significance, particularly in the context of integrated management of streams and aquifers. Techniques assessing riverbed flow and solute patterns are often limited to the local scale. When related to the multi-scale pattern of hydrogeologic and geomorphic features controlling stream, hyporheic and groundwater fluxes, they can improve larger scale predictions of flow and solute behaviour at the GSI. This study develops a conceptual model of riverbed flow and solute patterns, and tests it in a 4th order stream in the UK. It assesses the interaction between large scale subsurface flowpaths, driven by the distribution of bedrock outcrops, and the expansion and closure of alluvial deposits, and small-scale hyporheic flowpaths, driven by riffle-pool sequences. It uses two networks of riverbed mini-piezometers and multi-level samplers: network 1, across fifteen sites in a 7.2 km length of river in unconstrained (open alluvial valley), asymmetric (bedrock outcropping on one bank) and constrained (bedrock on both banks) contexts; and network 2, across six riffle-pool sequences in a 350-m reach, at the transition between asymmetric/unconstrained and constrained contexts. Subsurface flowpaths and stream-water infiltration were deduced by relating vertical exchange fluxes to stream and pore-water patterns of conservative natural tracers. Biogeochemical processes were highlighted using reactive natural tracers. At network 2, measurements of surface water profiles and riverbed coring were also undertaken, and dissolved metal concentrations in the first 15 cm of sediments assessed using gel probes. Network 1 was sampled twice. Monthly

  20. COAL PARTICLE FLOW PATTERNS FOR O2 ENRICHED, LOW NOx BURNERS

    Energy Technology Data Exchange (ETDEWEB)

    Jennifer L. Sinclair

    2001-09-30

    Over the past year, the hot flow studies have focused on the validation of a novel 2M near-flame combustion furnace. The 2M furnace was specifically designed to investigate burner aerodynamics and flame stability phenomena. Key accomplishments include completion of coal & oxygen mass balance calculations and derivation of emission conversion equations, upgrade of furnace equipment and flame safety systems, shakedown testing and partial completion of a parametric flame stability study. These activities are described in detail below along with a description of the 2M furnace and support systems.

  1. CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller

    Directory of Open Access Journals (Sweden)

    Devi Tamphasana Thiyam

    2012-01-01

    Full Text Available Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial of hydrodynamics (velocity and turbulence field in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6 impeller. Three speeds (N=296, 638 & 844.6 rpm have been considered for this study. The angular variations of hydrodynamics of stirred tank were found very less as compared to axial and radial variations.

  2. Subcutaneous adipose tissue blood flow in the forefoot during 24 hours. Labeling pattern and reproducibility

    DEFF Research Database (Denmark)

    Jelnes, Rolf; Bülow, J; Tønnesen, K H

    1987-01-01

    Wash-out of 133xenon from a local depot in the subcutaneous adipose tissue in the forefoot was measured continuously during 24 hours on subsequent recordings in 51 feet (normal circulation: 10, intermittent claudication: 22 and ischaemic nocturnal rest pain: 19) with a mean time interval of 26 da...... was calculated to 10%, and for the ratio of blood flow from day to night to 5%. The method is thus considered apt as a monitor in the treatment of peripheral vascular disease, for example, surgery and medical therapy. As predominant source of error is the formation of oedema....

  3. Anisotropic stress accumulation in cooling lava flows and resulting fracture patterns: Insights from starch-water desiccation experiments

    Science.gov (United States)

    Lodge, Robert W. D.; Lescinsky, David T.

    2009-09-01

    Desiccation of starch-water slurries is a useful analog for the production of polygonal fractures/columnar joints in cooling lava flows. When left to dry completely, a simple mixture of 1:1 starch and water will produce columns that appear remarkably similar to natural columnar joints formed in cooled lava flows. Columns form when the accumulation of isotropic stress exceeds the tensile strength of a material, at which point a fracture forms and advances through the material perpendicular to the desiccating surface. Individual fractures will initially form orthogonal to the desiccation surface but will quickly evolve into a hexagonal fracture network that advances incrementally through the material. However, some fracture patterns found within natural lava flows are not hexagonal ( Lodge and Lescinsky, 2009-this issue), but rather have fracture lengths that are much longer than the distance to adjacent fractures. These fractures are commonly found at lava flows that have interacted with glacial ice during emplacement. The purpose of this study is to utilize starch analog experiments to better understand the formation of these fractures and the stress regimes responsible for their non-hexagonal patterns. To simulate anisotropic conditions during cooling, the starch slurry was poured into a container with a movable wall that was attached to a screw-type jack. The jack was then set to slowly extend or retract while the slurry desiccated. This resulted in either a decrease or increase in the chamber cross-sectional area thus creating compressional or extensional regimes. Decreasing chamber area (DCA) experiments resulted in fractures with larger lengths parallel to the direction of wall movement (also direction of compression). It also caused localized thrust faulting and curved column development. Increasing chamber area (ICA) experiments produced a zone of horizontal column development along the expanding margin (produced when the wall detached from the sample

  4. Investigation of Vortical Flow Patterns in the Near Field of a Dynamic Low-Aspect-Ratio Cylinder

    Science.gov (United States)

    Gildersleeve, Samantha; Amitay, Michael

    2016-11-01

    The flowfield and associated flow structures of a low-aspect-ratio cylindrical pin were investigated experimentally in the near-field as the pin underwent wall-normal periodic oscillations. Under dynamic conditions, the pin is driven at the natural wake shedding frequency with an amplitude of 33% of its mean height. Additionally, a static pin was also tested at various mean heights of 0.5, 1.0, and 1.5 times the local boundary layer thickness to explore the effect of the mean height on the flowfield. Three-dimensional flowfields were reconstructed and analyzed from SPIV measurements where data were collected along streamwise planes for several spanwise locations under static and dynamic conditions. The study focuses on the incoming boundary layer as it interacts with the pin, as well as two main vortical formations: the arch-type vortex and the horseshoe vortex. Under dynamic conditions, the upstream boundary layer is thinner, relative to the baseline, and the downwash in the wake increases, resulting in a reduced wake deficit. These results indicate enhanced strength of the aforementioned vortical flow patterns under dynamic conditions. The flow structures in the near-field of the static/dynamic cylinder will be discussed in further detail. Supported by The Boeing Company.

  5. Computational study: The influence of omni-directional guide vane on the flow pattern characteristic around Savonius wind turbine

    Science.gov (United States)

    Wicaksono, Yoga Arob; Tjahjana, D. D. D. P.

    2017-01-01

    Standart Savonius wind turbine have a low performance such as low coefficient of power and low coefficient of torque compared with another type of wind turbine. This phenomenon occurs because the wind stream can cause the negative pressure at the returning rotor. To solve this problem, standard Savonius combined with Omni Directional Guide Vane (ODGV) proposed. The aim of this research is to study the influence of ODGV on the flow pattern characteristic around of Savonius wind turbine. The numerical model is based on the Navier-Stokes equations with the standard k-ɛ turbulent model. This equation solved by a finite volume discretization method. This case was analyzed by commercial computational fluid dynamics solver such as SolidWorks Flow Simulations. Simulations were performed at the different wind directions; there are 0°, 30°,60° at 4 m/s wind speed. The numerical method validated with the past experimental data. The result indicated that the ODGV able to augment air flow to advancing rotor and decrease the negative pressure in the upstream of returning rotor compared to the bare Savonius wind turbine.

  6. The simulated air flow pattern around a moving animal transport vehicle as the basis for a prospective biosecurity risk assessment

    Directory of Open Access Journals (Sweden)

    Jens Seedorf

    2017-08-01

    Full Text Available Research that investigates bioaerosol emissions from animal transport vehicles (ATVs and their importance in the spread of harmful airborne agents while the ATVs travel on roads is limited. To investigate the dynamical behaviour of theoretically released particles from a moving ATV, the open-source computational fluid dynamics (CFD software OpenFOAM was used to calculate the external and internal air flow fields with passive and forced ventilated openings of a common ATV moving at a speed of 80 km/h. In addition to a computed flow rate of approximately 40,000 m3/h crossing the interior of the ATV, the visualization of the trajectories has demonstrated distinct patterns of the spatial distribution of potentially released bioaerosols in the vicinity of the ATV. Although the front openings show the highest air flow to the outside, the recirculations of air masses between the interior of the ATV and the atmosphere also occur, which complicate the emission and the dispersion characterizations. To specify the future emission rates of ATVs, a database of bioaerosol concentrations within the ATV is necessary in conjunction with high-performance computing resources to simulate the potential dispersion of bioaerosols in the environment.

  7. Different Bleeding Patterns with the Use of Levonorgestrel Intrauterine System: Are They Associated with Changes in Uterine Artery Blood Flow?

    Directory of Open Access Journals (Sweden)

    Carlo Bastianelli

    2014-01-01

    Full Text Available Objective. Evaluate if different bleeding patterns associated with the use of the levonorgestrel intrauterine system (LNG-IUS are associated with different uterine and endometrial vascularization patterns, as evidenced by ultrasound power Doppler analysis. Methodology. A longitudinal study, with each subject acting as its own control was conducted between January 2010 and December 2012. Healthy volunteers with a history of heavy but cyclic and regular menstrual cycles were enrolled in the study. Ultrasonographic examination was performed before and after six months of LNG-IUS placement: uterine volume, endometrial thickness, and subendometrial and myometrial Doppler blood flow patterns have been evaluated. Results. A total of 32 women were enrolled out of 186 initially screened. At six months of follow-up, all subjects showed a reduction in menstrual blood loss; for analysis, they were retrospectively divided into 3 groups: normal cycling women (Group I, amenorrheic women (Group II, and women with prolonged bleedings (Group III. Intergroup analysis documented a statistically significant difference in endometrial thickness among the three groups; in addition, mean pulsatility index (PI and resistance index (RI in the spiral arteries were significantly lower in Group I and Group III compared to Group II. This difference persisted also when comparing—within subjects of Group III—mean PI and RI mean values before and after insertion. Conclusions. The LNG-IUS not only altered endometrial thickness, but—in women with prolonged bleedings—also significantly changed uterine artery blood flow. Further studies are needed to confirm these results and enable gynecologists to properly counsel women, improving initial continuation rates.

  8. An ice flow modeling perspective on bedrock adjustment patterns of the Greenland ice sheet

    Directory of Open Access Journals (Sweden)

    M. Olaizola

    2012-11-01

    Full Text Available Since the launch in 2002 of the Gravity Recovery and Climate Experiment (GRACE satellites, several estimates of the mass balance of the Greenland ice sheet (GrIS have been produced. To obtain ice mass changes, the GRACE data need to be corrected for the effect of deformation changes of the Earth's crust. Recently, a new method has been proposed where ice mass changes and bedrock changes are simultaneously solved. Results show bedrock subsidence over almost the entirety of Greenland in combination with ice mass loss which is only half of the currently standing estimates. This subsidence can be an elastic response, but it may however also be a delayed response to past changes. In this study we test whether these subsidence patterns are consistent with ice dynamical modeling results. We use a 3-D ice sheet–bedrock model with a surface mass balance forcing based on a mass balance gradient approach to study the pattern and magnitude of bedrock changes in Greenland. Different mass balance forcings are used. Simulations since the Last Glacial Maximum yield a bedrock delay with respect to the mass balance forcing of nearly 3000 yr and an average uplift at present of 0.3 mm yr−1. The spatial pattern of bedrock changes shows a small central subsidence as well as more intense uplift in the south. These results are not compatible with the gravity based reconstructions showing a subsidence with a maximum in central Greenland, thereby questioning whether the claim of halving of the ice mass change is justified.

  9. Quantification of disturbed wall shear stress patterns in complex cardiovascular flows

    Science.gov (United States)

    Arzani, Amirhossein; Shadden, Shawn C.

    2014-11-01

    Wall shear stress (WSS) affects the cardiovascular system in numerous ways, and is thought to play an important role in the pathology of many cardiovascular diseases. The (endothelial) cells lining the inner wall of blood vessels, and perhaps the cells inside the vessel wall, can actively sense WSS and respond both chemically and mechanically. The complexity of WSS in cardiovascular flows extends both spatially and temporally. Furthermore, WSS has magnitude and direction. These facets make simple quantification of WSS in cardiovascular applications difficult. In this study we propose a framework to quantify measures such as WSS angle gradient, WSS magnitude gradient, WSS angle time derivative and WSS magnitude time derivative. We will explain the relation of these parameters to the tensorial WSS gradient and WSS vector time derivative, and propose a new methodology to unify these concepts into a single measure. The correlation between these metrics and more common WSS metrics used in the literature will be demonstrated. For demonstration, these methods will be used for the quantification of complex blood flow inside abdominal aortic aneurysms.

  10. Research on Flow Pattern of Nitrogen Tetroxide Liquid in the Different Bend Radii Pipes

    Directory of Open Access Journals (Sweden)

    Hao Pengfei

    2016-01-01

    Full Text Available N2O4 is a common rocket fuel propellants, it has the characteristics of low boiling point and a large viscosity , the friction between viscosity fluids and pipeline dramatic leads to a huge sticky heat, therefore, the vaporization phenomenon often occurs in the pipeline, particularly in bending of the viscous heat. For this reason, the research of the different bending radii vaporized fluid conditions for optimizing the piping and precise the filling flow is significant. In this paper, the MIXTURE mixed flow model is used to achieve the numerical simulation the pipelines filling of the three different bending radii, it still have not solved the mass transfer problem between the different phases. Therefore, the custom functions are needed to define the mass transfer problems from the liquid phase to the vapor phase. Though the contrast among the volume phase cloud of six different elbow models , we have the following conclusions: 1 In the entire pipeline transportation, the distribution vaporization rate from the inlet pipe to the outlet pipe follows the distribution of the first increasing and then decreasing, the gas rates of the elbow area is highest; 2Analyzing the sticky heat for different bend radii, we have the conclusion that the lowest bending vaporization the of the optimal radius is 0.45m. The above conclusions are drawn in good agreement with the actual law, can effectively guide the engineering practice, have important significance for the future design for the optimization of the fuel pipeline transportation.

  11. Interdependencies of aortic arch secondary flow patterns, geometry, and age analysed by 4-dimensional phase contrast magnetic resonance imaging at 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Frydrychowicz, Alex [University Hospital Schleswig-Holstein, Clinic for Radiology and Nuclear Medicine, Luebeck (Germany); Berger, Alexander; Russe, Maximilian F.; Bock, Jelena [University Hospital Freiburg, Department of Radiology, Medical Physics, Freiburg (Germany); Munoz del Rio, Alejandro [University of Wisconsin - Madison, Departments of Radiology and Medical Physics, Madison, WI (United States); Harloff, Andreas [University Hospital Freiburg, Department of Neurology and Clinical Neurophysiology, Freiburg (Germany); Markl, Michael [University Hospital Freiburg, Department of Radiology, Medical Physics, Freiburg (Germany); Northwestern University, Departments of Radiology and Biomedical Engineering, Chicago, IL (United States)

    2012-05-15

    It was the aim to analyse the impact of age, aortic arch geometry, and size on secondary flow patterns such as helix and vortex flow derived from flow-sensitive magnetic resonance imaging (4D PC-MRI). 62 subjects (age range = 20-80 years) without circumscribed pathologies of the thoracic aorta (ascending aortic (AAo) diameter: 3.2 {+-} 0.6 cm [range 2.2-5.1]) were examined by 4D PC-MRI after IRB-approval and written informed consent. Blood flow visualisation based on streamlines and time-resolved 3D particle traces was performed. Aortic diameter, shape (gothic, crook-shaped, cubic), angle, and age were correlated with existence and extent of secondary flow patterns (helicity, vortices); statistical modelling was performed. Helical flow was the typical pattern in standard crook-shaped aortic arches. With altered shapes and increasing age, helicity was less common. AAo diameter and age had the highest correlation (r = 0.69 and 0.68, respectively) with number of detected vortices. None of the other arch geometric or demographic variables (for all, P {>=} 0.177) improved statistical modelling. Substantially different secondary flow patterns can be observed in the normal thoracic aorta. Age and the AAo diameter were the parameters correlating best with presence and amount of vortices. Findings underline the importance of age- and geometry-matched control groups for haemodynamic studies. (orig.)

  12. Development of active regions: flows, magnetic-field patterns and bordering effect

    CERN Document Server

    Getling, A V; Buchnev, A A

    2015-01-01

    A qualitative analysis is given to the data on the full magnetic and velocity vector fields in a growing sunspot group, recorded nearly simultaneously with the Solar Optical Telescope on the Hinode satellite. Observations of a young bipolar subregion developing within AR 11313 were carried out on 9-10 October 2011. Our aim was to form am idea about the consistency of the observed pattern with the well-known rising-tube model of the formation of bipolar acrive regions and sunspot groups. We find from our magnetograms that the distributions of the vertical [B_v] and the horizontal [B_h] component of the magnetic field over the area of the magnetic subregion are spatially well correlated; in contrast, the rise of a flux-tube loop would result in a qualitatively different pattern, with the maxima of the two magnetic-field components spatially separated: the vertical field would be the strongest where either spot emerges, while the maximum horizontal-field strengths would be reached in between them. A specific fea...

  13. Reduction of the ambiguity of karst aquifer modeling through pattern matching of groundwater flow and transport

    Science.gov (United States)

    Oehlmann, Sandra; Geyer, Tobias; Licha, Tobias; Sauter, Martin

    2014-05-01

    Distributive numerical simulations are an effective, process-based method for predicting groundwater resources and quality. They are based on conceptual hydrogeological models that characterize the properties of the catchment area and aquifer. Karst systems play an important role in water supply worldwide. Conceptual models are however difficult to build because of the highly developed heterogeneity of the systems. The geometry and properties of highly conductive karst conduits are generally unknown and difficult to characterize with field experiments. Due to these uncertainties numerical models of karst areas usually cannot simulate the hydraulic head distribution in the area, spring discharge and tracer breakthrough curves simultaneously on catchment scale. Especially in complex hydrogeological systems, this approach would reduce model ambiguity, which is prerequisite to predict groundwater resources and pollution risks. In this work, a distributive numerical groundwater flow and transport model was built for a highly heterogeneous karst aquifer in south-western Germany. For this aim, a solute transport interface for one-dimensional pipes was implemented in the software Comsol Multiphysics® and coupled to the standard three-dimensional solute transport interface for domains. The model was calibrated and hydraulic parameters could be obtained. The simulation was matched to the steady-state hydraulic head distribution in the model area, the spring discharge of several springs and the transport velocities of two tracer tests. Furthermore, other measured parameters such as hydraulic conductivity of the fissured matrix and the maximal karst conduit volume were available for model calibration. Parameter studies were performed for several karst conduit geometries to analyze their influence in a large-scale heterogeneous karst system. Results show that it is not only possible to derive a consistent flow and transport model for a 150 km2 karst area to be employed as a

  14. 树干液流径向分布格局研究进展%Review of advances in radial patterns of stem sap flow

    Institute of Scientific and Technical Information of China (English)

    徐飞; 杨风亭; 王辉民; 戴晓琴

    2012-01-01

    Variability in radial patterns of sap flow is the main source of error in evaluating individual and stand transpiration using thermal techniques. Thus, it is necessary to understand and quantify radial patterns of stem sap flow before accurate estimation of forest transpiration can be conducted. We discuss the methods used to determine radial patterns of sap flow and summarize four main patterns of stem sap flow. We also review the effects of inner structure characteristics and environmental factors on radial patterns of sap flow. In addition, we present the diurnal and seasonal variability in radial patterns of sap flow. Lastly, we propose possible problems in resent research on radial patterns of stem sap flow.%树干液流径向分布的不均匀性是引起热技术估算单株乃至林分蒸腾误差的主要来源.因此,了解树干液流径向分布格局并将其定量化,成为利用热扩散和热脉冲技术准确估算森林蒸腾的必要条件.该文详细介绍了树干液流径向分布格局的研究方法,总结了目前4种常见的树干液流的径向分布格局,分析了影响树干液流径向分布格局的内部结构因素和外部环境因素,阐明了树干液流径向分布格局的时间动态特征及其影响因素,并提出目前研究中存在的问题和可能的解决方法.

  15. In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Kyoden, Tomoaki, E-mail: kyouden@nc-toyama.ac.jp; Naruki, Shoji; Akiguchi, Shunsuke; Momose, Noboru; Homae, Tomotaka; Hachiga, Tadashi [National Institute of Technology, Toyama College, 1-2 Ebie-Neriya, Imizu, Toyama 933-0293 (Japan); Ishida, Hiroki [Department of Applied Physics, Faculty of Science, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005 (Japan); Andoh, Tsugunobu [Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194 (Japan); Takada, Yogo [Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585 (Japan)

    2016-08-28

    Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensional space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was detected using the developed speckle pattern, which is created by the skin construct and two beams in the flow channel. Finally, we showed the relationship between the signal intensity and the fringe pattern, undeveloped speckle, or developed speckle pattern based on the skin depth. The Doppler signals were not detected at deeper positions in the skin, which qualitatively indicates the depth limit for two-beam MLDV.

  16. Observation of the CSF pulsatile flow in an aqueduct using cine MRI with presaturation bolus tracking, (2); The classification of pulsatile-flow patterns in adult patients with ventriculomegaly

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Satoshi; Akada, Shouhiro; Deguchi, Itaru; Miwa, Tetsurou; Itoh, Hiroshi (Tokyo Medical Coll. (Japan))

    1991-12-01

    Various to-and-fro motion patterns of the CSF flow in an aqueduct were analyzed in ten normal volunteers, in ten patients with secondary normal-pressure hydrocephalus, in nine patients with idiopathic ventriculomegaly, and in five cases of brain atrophy using cine MRI with presaturation bolus tracking. The to-and-fro motion patterns were classified into four types. Type I; in which the velocity of the CSF in the aqueduct is slower than 15 mm/sec, and the duration of the flow in the caudal direction is longer than in the rostral. Type II; in which the velocity of the CSF in the aqueduct is faster than 15 mm/sec, and the duration of the flow in the caudal direction is longer than in the rostral. Type III; in which the velocity is relatively faster than Type I, but the duration of the flow in the caudal direction is shorter than in the rostral. Type IV; in which the velocity is slower than 15 mm/sec, and the duration of the flow in the caudal direction is shorter than in the rostral. In secondary normal-pressure hydrocephalus (NPH), the flow patterns were all of Type II. In idiopathic ventriculomegaly, the cases of which showed ventricular reflux on RI-cisternography, the flow patterns were divided into three types (II, III and IV). In the cases of brain atrophy, who did not show ventricular reflux on RI-cisternography, the flow patterns were all of Type I. We conclude that the evaluation of the CSF pulsatile flow in the aqueduct can give new clinical information for use in investigating the pathogenesis of the ventriculomegaly. (author).

  17. Experimental Studies of Flow Patterns of Different Fluids in a Partially Filled Rotating Cylinder

    Directory of Open Access Journals (Sweden)

    P.R. Mukunda

    2009-01-01

    Full Text Available An attempt has been made to investigate the various parameters affecting the fluid behaviour, partially filled in a rotating cylinder. When the cylinder is rotating at ‘high’ speed, a liquid forms a hollow cylinder. Different patterns are observed in the fluids for the rotatioal speeds below a critical speed. This study should give us some insight into molten metal behaviour during centrifugal casting. An extensive experimental investigation is required to obtain an appropriate functional relationship by knowing and understanding some dimensionless parameters. Here the effect of dimensionless parameters ε (which is 2 g/ω2d, where g, ω and d denotes gravitational acceleration, container rotation rate and inner diameter of liquid cylinder and G (number of times the gravity was studied as variation of rotation speed, viscosity and aspect ratio of the mould.

  18. A study of air flow patterns affecting pollutant concentrations in the Central Region of Mexico

    Science.gov (United States)

    Jazcilevich, Aron D.; García, Agustín. R.; Ruíz-Suárez, L. Gerardo

    Using a prognostic air quality model that includes actual emissions, air pollution regimes over the central region of Mexico are simulated. It is shown that due to the complex orography, vertical circular patterns develop over the metropolitan area of Mexico City. In this way reactive and non-reactive pollutants can travel near the surface, be transported vertically and land in an area opposite to its initial route due to convective downward currents. This changes the surface pollutant concentrations on the landing area. Also, it is shown that air pollution is transported near the surface from the metropolitan area of Mexico City through Chalco in the South-east corner of the Mexico Valley, to the Valley of Cuautla affecting this area.

  19. Identifiability of sorption parameters in stirred flow-through reactor experiments and their identification with a Bayesian approach.

    Science.gov (United States)

    Nicoulaud-Gouin, V; Garcia-Sanchez, L; Giacalone, M; Attard, J C; Martin-Garin, A; Bois, F Y

    2016-10-01

    This paper addresses the methodological conditions -particularly experimental design and statistical inference- ensuring the identifiability of sorption parameters from breakthrough curves measured during stirred flow-through reactor experiments also known as continuous flow stirred-tank reactor (CSTR) experiments. The equilibrium-kinetic (EK) sorption model was selected as nonequilibrium parameterization embedding the Kd approach. Parameter identifiability was studied formally on the equations governing outlet concentrations. It was also studied numerically on 6 simulated CSTR experiments on a soil with known equilibrium-kinetic sorption parameters. EK sorption parameters can not be identified from a single breakthrough curve of a CSTR experiment, because Kd,1 and k(-) were diagnosed collinear. For pairs of CSTR experiments, Bayesian inference allowed to select the correct models of sorption and error among sorption alternatives. Bayesian inference was conducted with SAMCAT software (Sensitivity Analysis and Markov Chain simulations Applied to Transfer models) which launched the simulations through the embedded simulation engine GNU-MCSim, and automated their configuration and post-processing. Experimental designs consisting in varying flow rates between experiments reaching equilibrium at contamination stage were found optimal, because they simultaneously gave accurate sorption parameters and predictions. Bayesian results were comparable to maximum likehood method but they avoided convergence problems, the marginal likelihood allowed to compare all models, and credible interval gave directly the uncertainty of sorption parameters θ. Although these findings are limited to the specific conditions studied here, in particular the considered sorption model, the chosen parameter values and error structure, they help in the conception and analysis of future CSTR experiments with radionuclides whose kinetic behaviour is suspected.

  20. Effect of the spray pattern, water flow rate, and cutting position on the cutting efficiency of high-speed dental handpieces.

    Science.gov (United States)

    Yang, Wen-jie; Sun, Jian

    2013-01-01

    The aim of this study was to evaluate the effect of the spray pattern, water flow rate, and cutting position on the cutting efficiency of high-speed dental handpieces. One- and three-port high-speed handpieces were selected. Cutting efficiency (mm/s) in different cutting positions was evaluated in vitro on machinable ceramic underwater flow rates of 15, 25, and 35 mL/min. Statistical analysis revealed significant differences in cutting efficiency for the various cutting positions and flow rates. The authors recommend multiport handpieces with a flow rate greater than 30 mL/min for use in clinical practice, especially during groove cutting.

  1. Pattern of shallow ground water flow at Mount Princeton Hot Springs, Colorado, using geoelectrical methods

    Science.gov (United States)

    Richards, K.; Revil, A.; Jardani, A.; Henderson, F.; Batzle, M.; Haas, A.

    2010-12-01

    In geothermal fields, open faults and fractures often act as high permeability pathways bringing hydrothermal fluids to the surface from deep reservoirs. The Mount Princeton area, in south-central Colorado, is an area that has an active geothermal system related to faulting and is therefore a suitable natural laboratory to test geophysical methods. The Sawatch range-front normal fault bordering the half-graben of the Upper Arkansas valley is characterized by a right-lateral offset at Mount Princeton Hot springs. This offset is associated with the Chalk Cliffs of hydrothermally altered quartz monzonite. Because fault identification in this area is complicated by quaternary deposits (including glacial and fluvial deposits), we use DC electrical resistivity tomography and self-potential mapping to identify preferential fluid flow pathways. The geophysical data (over 5600 resistivity and 2700 self-potential measurements) provide evidence of the existence of a dextral strike slip fault zone (Fault B) responsible for the offset of the Sawatch fault. A segment of this dextral strike slip fault (termed U1) is acting as the dominant vertical flow path bringing thermal waters to a shallow unconfined aquifer. Upwelling of the thermal waters is also observed at two zones (U2 and U3) of an open fracture called Fault A. This fault is located at the tip of the Sawatch fault and is likely associated with an extensional strain regime in this area. Self-potential measurements are used to estimate the flux of upwelling thermal water. The upflow estimate (4 ± 1 × 10 3 m 3/day for the open segment of the Fault B and 2 ± 1 × 10 3 m 3/day for Fault A) from the geophysical data is remarkably consistent with the downstream Mt. Princeton hot water production (4.3-4.9) × 10 3 m 3/day at approximately 60-86 °C). A temperature map indicates that a third upwelling zone termed U4 may exist at the southern tip of the Sawatch fault.

  2. 混合遗传算法在CSTR中应用%Application of hybrid genetic algorithm to CSTR system

    Institute of Scientific and Technical Information of China (English)

    赵超; 张志君

    2006-01-01

    针对遗传算法(GA)收敛速度慢,不利于在实时控制中应用这一问题,构造出一种快速收敛的混合遗传算法(HGA),该算法利用遗传算法的全局搜索能力,并采用Nelder-Mead单纯形法来加强算法的局部搜索能力,加快了算法的收敛效率. 将基于该混合遗传算法的模型参考自适应控制方法引入连续搅拌反应釜(CSTR)这一复杂的非线性系统,根据参考模型的输出,通过混合遗传算法对控制系统的PID参数进行在线寻优和在线调整,以达到参考模型所要求的控制效果,仿真结果表明了该方法的良好控制性能.

  3. Enhancement of biogas production by co-digestion of potato pulp with cow manure in a CSTR system.

    Science.gov (United States)

    Sanaei-Moghadam, Akbar; Abbaspour-Fard, Mohammad Hossein; Aghel, Hasan; Aghkhani, Mohammad Hossein; Abedini-Torghabeh, Javad

    2014-08-01

    Anaerobic digestion (AD) process is a well-established method to generate energy from the organic wastes both from the environmental and economical perspectives. The purpose of present study is to evaluate energy production from potato wastes by incorporating cow manure into the process. Firstly, a laboratory pilot of one-stage biogas production was designed and built according to continuously stirred tank reactor (CSTR) system. The setup was able to automatically control the environmental conditions of the process including temperature, duration, and rate of stirring. AD experiment was exclusively performed on co-digestion of potato peel (PP) and cow manure (CM) in three levels of mixing ratio including 20:80, 50:50, 80:20 (PP:CM), and 0:100 as control treatment based on the volatile solid (VS) weight without adding initial inoculums. After hydraulic retention time (HRT) of 50 days on average 193, 256, 348, and 149 norm liter (LN) (kg VS)(-1), methane was produced for different mixing ratios, respectively. Statistical analysis shows that these gas productions are significantly different. The average energy was determined based on the produced methane which was about 2.8 kWh (kg VS)(-1), implying a significant energy production potential. The average chemical oxygen demand (COD) removal of treatments was about 61%, showing that it can be leached significantly with high organic matter by the employed pilot. The energy efficiency of 92% of the process also showed the optimum control of the process by the pilot.

  4. Start-up and stabilization of an Anammox process from a non-acclimatized sludge in CSTR.

    Science.gov (United States)

    Bagchi, Samik; Biswas, Rima; Nandy, Tapas

    2010-09-01

    Development of an Anammox (anaerobic ammonium oxidation) process using non-acclimatized sludge requires a long start-up period owing to the very slow growth rate of Anammox bacteria. This article addresses the issue of achieving a shorter start-up period for Anammox activity in a well-mixed continuously stirred tank reactor (CSTR) using non-acclimatized anaerobic sludge. Proper selection of enrichment conditions and low stirring speed of 30 +/- 5 rpm resulted in a shorter start-up period (82 days). Activity tests revealed the microbial community structure of Anammox micro-granules. Ammonia-oxidizing bacteria (AOB) were found on the surface and on the outer most layers of granules while nitrite-oxidizing bacteria (NOB) and Anammox bacteria were present inside. Fine-tuning of influent NO2(-)/NH4+ ratio allowed Anammox activity to be maintained when mixed microbial populations were present. The maximum nitrogen removal rate achieved in the system was 0.216 kg N/(m(3) day) with a maximum specific nitrogen removal rate of 0.434 g N/(g VSS day). During the study period, Anammox activity was not inhibited by pH changes and free ammonia toxicity.

  5. Mixed culture polyhydroxyalkanoates production from sugar molasses: the use of a 2-stage CSTR system for culture selection.

    Science.gov (United States)

    Albuquerque, M G E; Concas, S; Bengtsson, S; Reis, M A M

    2010-09-01

    Polyhydroxyalkanoates (PHAs) are promising biodegradable polymers. The use of mixed microbial cultures (MMC) and low cost feedstocks have a positive impact on the cost-effectiveness of the process. It has typically been carried out in Sequencing Batch Reactors (SBR). In this study, a 2-stage CSTR system (under Feast and Famine conditions) was used to effectively select for PHA-storing organisms using fermented molasses as feedstock. The effect of influent substrate concentration (60-120 Cmmol VFA/L) and HRT ratio between the reactors (0.2-0.5h/h) on the system's selection efficiency was assessed. It was shown that Feast reactor residual substrate concentration impacted on the selective pressure for PHA storage (due to substrate-dependent kinetic limitation). Moreover, a residual substrate concentration coming from the Feast to the Famine reactor did not jeopardize the physiological adaptation required for enhanced PHA storage. The culture reached a maximum PHA content of 61%. This success opens new perspectives to the use of wastewater treatment infrastructure for PHA production, thus valorizing either excess sludge or wastewaters.

  6. Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR).

    Science.gov (United States)

    Li, Yeqing; Zhang, Ruihong; He, Yanfeng; Zhang, Chenyu; Liu, Xiaoying; Chen, Chang; Liu, Guangqing

    2014-03-01

    Anaerobic co-digestion of chicken manure and corn stover in batch and CSTR were investigated. The batch co-digestion tests were performed at an initial volatile solid (VS) concentration of 3gVS/L, carbon-to-nitrogen (C/N) ratio of 20, and retention time of 30d. The methane yield was determined to be 281±12mL/gVSadded. Continuous reactor was carried out with feeding concentration of 12% total solids and C/N ratio of 20 at organic loading rates (OLRs) of 1-4gVS/L/d. Results showed that at OLR of 4gVS/L/d, stable and preferable methane yield of 223±7mL/gVSadded was found, which was equal to energy yield (EY) of 8.0±0.3MJ/kgVSadded. Post-digestion of digestate gave extra EY of 1.5-2.6MJ/kgVSadded. Pyrolysis of digestate provided additional EY of 6.1MJ/kgVSadded. Pyrolysis can be a promising technique to reduce biogas residues and to produce valuable gas products simultaneously.

  7. Influence of organic loading rate on methane production in a CSTR from physicochemical sludge generated in a poultry slaughterhouse.

    Science.gov (United States)

    López-Escobar, Luis A; Martínez-Hernández, Sergio; Corte-Cano, Grisel; Méndez-Contreras, Juan M

    2014-01-01

    The influence of the increase of the organic loading rate (OLR) on methane production in a continuous stirred-tank reactor (CSTR) from physicochemical sludge generated in a poultry slaughterhouse was evaluated. Total solid (TS) to obtain OLR of 1, 5, 10 and 15 g VS L(-1) day(-1), with hydraulic retention times of 29, 6, 6 and 4, respectively, were conditioned. The results showed a decrease in pH levels and an increase in the theoretical volatile fatty acids (VFA). While the yield of methane production decreased from 0.48 to 0.10 LCH4/g VSremoved, respectively, the OLR-10 managed on average 38% removal of volatile solids (VS) and a yield biogas production of 0.81 Lbiogas g(-1) VSremoved and 1.35 L day(-1). This suggests that the OLR increases in an anaerobic system from physicochemical sludge only inhibits the methanogenic metabolism, because there is still substrate consumption and biogas production.

  8. [Analysis of dynamic characteristics for fermentative hydrogen-producing bacteria community and hydrogen producing capability in CSTR].

    Science.gov (United States)

    Song, Jia-Xiu; Ren, Nan-Qi; Chen, Ying; An, Dong

    2009-07-15

    The start into the types of fermentation was carried out by pH adjustment from 4.2 to 6.0 in CSTR system. The process of transforming of hydrogen production and dynamic community of bacteria were studied. The results showed that with the organic load maintained at (33 +/- 1) kg/(m3 x d), there was no change in 10 d for the type of fermentation, the amount of hydrogen does not reduce in 8 d. After 15 d, the system was transformed from the ethanol-based type into butyric acid type and water alkalinity was from 250 mg/L to 2450 mg/L. The use of fluorescence in situ hybridization (FISH) system was in response to the 3 groups of micro-organisms. It was found that in the process of transforming, Clostridium cluster XI increases and Clostridium cluster I and II decreases. Enterobacteriaceae always existed with no change. The microbial growth must be considered with hydrogen production capability. The average hydrogen production rate reached to 23.6 mol/(kg x d) with Clostridium cluster I and II dominated in fermentation reactor.

  9. Effect of die shape on the metal flow pattern during direct extrusion process

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, N.; Solomon, I.

    2010-07-01

    The geometric shape of the tools is the main factor by which an optimum technological process can be developed. In the case of extrusion process the strain distribution and other important variables that influence material structure, such as hydrostatic stress, are strongly dependent on the geometry of the die. Careful design of the extrusion die profile can therefore control the product structure and can be used to minimise the amount of inhomogeneity imparted into the product. A possibility to minimise the amount of product inhomogeneity is the using of a flat die with a fillet radius in front to the bearing surface with leads to a minimum dead zone and consequently to a minimum friction at billet-container interface. In the case of aluminium alloy type 2024, for an extrusion ratio of R=8.5, good results were obtained with a fillet radius of 3.0 mm. The experimental data have been used for the finite element numerical simulation of the extrusion process. The data obtained by numerical simulation with FORGE2 programme confirm the theoretical and experimental outcomes. The aim of this paper is to study the influence of such flat die on the material flow during direct extrusion process and consequently on extruded product microstructure and mechanical properties. (Author).

  10. Effect of welding speed on the material flow patterns in friction stir welding of AZ31 magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; Wu Huiqiang; Huang Jihua; LIN Sanbao; WU Lin

    2007-01-01

    The clear zigzag-line pattern on transverse cross sections can be used to explain the formation mechanism of the weld nugget when friction stir welded AZ31 magnesium alloy without any other insert material is used as mark. It provides a simple and useful method to research the joining mechanism of friction stir welding. The rotation speed is kept at 1000 r/min and the welding speed changes from 120 mm/min to 600 mm/min. The macrostructure on the transverse cross section was divided into several parts by faying surface. The results show that the shape and formation procedure of the weld nugget change with the welding speed. There are two main material flows in the weld nugget: one is from the advancing side and the other is from the retreating side. A simple model on the weld nugget formation of FSW is presented in this article.

  11. Indoor Airflow Patterns, Dispersion of Human Exhalation Flow and Risk of Airborne Cross-Infection between People in a Room

    DEFF Research Database (Denmark)

    Olmedo, Inés

    prevalent transmission routes. Airborne cross-infection of diseases is caused by the transmission of pathogens, such as viruses or bacteria, between people and across environments. When a person is breathing, talking, sneezing or coughing, small particles, which may carry biological contaminants, are spread...... in the air. These tiny particles or droplet nuclei can follow the air flow pattern in the room and produce high contaminant concentration in different areas of the indoor environment. This fact can provoke a high exposure to exhaled contaminants and a risk of cross-infection to a susceptible person situated...... the persons. This thesis analyzes some of these parameters in the influence of cross-infection risk between two people in a room, which are simulated by two breathing thermal manikins. One of the manikins is considered the source of contaminants, which is exhaling contaminated air through the mouth...

  12. First identification of sub- and supercritical convection patterns from ‘GeoFlow’, the geophysical flow simulation experiment integrated in Fluid Science Laboratory

    Science.gov (United States)

    Futterer, B.; Egbers, C.; Dahley, N.; Koch, S.; Jehring, L.

    2010-01-01

    Physical mechanisms of thermally driven rotating fluids are important for a large number of geophysical problems, e.g. to explain the convection of the Earth's liquid outer core. Objective of the 'GeoFlow' experiment is to study stability, pattern formation, and transition to chaos of thermal convection in fluid-filled concentric, co-axially rotating spheres. This experiment is integrated in the Fluid Science Laboratory of the European COLUMBUS module on International Space Station. Fluid dynamics of the experiment was predicted with numerical simulations by means of a spectral code. In the non-rotating case the onset of convection bifurcated into steady fluid flow. Here patterns of convection showed co-existing states with axisymmetric, cubic and pentagonal modes. Transition to chaos was in the form of sudden onset. For the thermal convection in rotating spheres the onset of first instability showed an increase of modes for higher parameter regime. Transition was from steady via periodic to chaotic behaviour. Convection patterns of the experiment are observed with the Wollaston shearing interferometry. Images are in terms of interferograms with fringe patterns corresponding to special convective flows. A first glance at the images showed the classification of sub- and supercritical flow regimes. Aligned with numerical data a shift between experiment and numerical simulation was identified. Identification of convection patterns in interferograms was demonstrated for the example of a supercritical flow.

  13. Contrasting demographic history and gene flow patterns of two mangrove species on either side of the Central American Isthmus.

    Science.gov (United States)

    Cerón-Souza, Ivania; Gonzalez, Elena G; Schwarzbach, Andrea E; Salas-Leiva, Dayana E; Rivera-Ocasio, Elsie; Toro-Perea, Nelson; Bermingham, Eldredge; McMillan, W Owen

    2015-08-01

    Comparative phylogeography offers a unique opportunity to understand the interplay between past environmental events and life-history traits on diversification of unrelated but co-distributed species. Here, we examined the effects of the quaternary climate fluctuations and palaeomarine currents and present-day marine currents on the extant patterns of genetic diversity in the two most conspicuous mangrove species of the Neotropics. The black (Avicennia germinans, Avicenniaceae) and the red (Rhizophora mangle, Rhizophoraceae) mangroves have similar geographic ranges but are very distantly related and show striking differences on their life-history traits. We sampled 18 Atlantic and 26 Pacific locations for A. germinans (N = 292) and R. mangle (N = 422). We performed coalescence simulations using microsatellite diversity to test for evidence of population change associated with quaternary climate fluctuations. In addition, we examined whether patterns of genetic variation were consistent with the directions of major marine (historical and present day) currents in the region. Our demographic analysis was grounded within a phylogeographic framework provided by the sequence analysis of two chloroplasts and one flanking microsatellite region in a subsample of individuals. The two mangrove species shared similar biogeographic histories including: (1) strong genetic breaks between Atlantic and Pacific ocean basins associated with the final closure of the Central American Isthmus (CAI), (2) evidence for simultaneous population declines between the mid-Pleistocene and early Holocene, (3) asymmetric historical migration with higher gene flow from the Atlantic to the Pacific oceans following the direction of the palaeomarine current, and (4) contemporary gene flow between West Africa and South America following the major Atlantic Ocean currents. Despite the remarkable differences in life-history traits of mangrove species, which should have had a strong influence on seed

  14. Associations between flow in paratibial perforating veins and great saphenous vein patterns of reflux

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Engelhorn

    2015-06-01

    Full Text Available Perforating veins contribute to chronic venous valvular insufficiency (CVVI, subset of CVI of lower extremities (LE. We investigated the role of medial, proximal calf paratibial perforating veins (PTPV. Women with PTPV reflux, diameter ≥3 mm, or tortuosity were selected among 2199 LE mappings. Duplex ultrasonography (US was performed standing. Reflux >0.5 s was abnormal. PTPV conditions were related to great saphenous vein (GSV patterns of reflux. US of 442 LE of 379 women were analyzed, all being Clinical-Etiology-Anatomy-Pathophysiology (CEAP classification C1, C2, and/or having intermittent, conditional swelling. Etiology was primary. Pathophysiology was reflux, not thrombosis or obstruction. Most PTPV drained (n=281, 64% of 442 or 13% of 2199, or were source (n=73, 17%/442, 3%/2199 of GSV reflux; 49 (11%/442, 2%/2199 had reflux not associated with GSV; 39 (9%/442, 2%/2199 did not have reflux. PTPV, when significative for CVVI, primarily drained-GSV reflux. PTPV was linked to reflux in 1 of 5 and was a major source of reflux in 1 of 20 legs. Detailed US of PTPV insured over 80% accuracy in CVVI mapping.

  15. Flow patterns and shear stress waveforms in intracranial aneurysms: The effect of pulsatility

    Science.gov (United States)

    Sotiropoulos, Fotis; Le, Trung; Borazjani, Iman

    2009-11-01

    The wall shear stress on the dome of intracranial aneurysms has been hypothesized to be an important factor in aneurysm pathology and depends strongly on the hemodynamics inside the dome. The importance of patient-specific geometry on the hemodynamics of aneurysms has long been established but the significance of patient-specific inflow waveform is largely unexplored. In this work we seek to systematically investigate and quantify the effects of inflow waveform on aneurysm hemodynamics. We carry out high resolution numerical simulations for an anatomic intracranial aneurysm obtained from 3D rotational angiography (3DRA) data for various inflow waveforms. We show that both the vortex formation process and wall-shear stress dynamics on the aneurysm dome depend strongly on the characteristics of the inflow waveform. We also present preliminary evidence suggesting that a simple non-dimensional number (named the Aneurysm number), incorporating both geometry and inflow waveform effects, could be a good qualitative predictor of the general hemodynamic patterns that will arise in a given aneurysm geometry for a particular waveform.

  16. Coherent transport and energy flow patterns in photosynthesis under incoherent excitation.

    Science.gov (United States)

    Pelzer, Kenley M; Can, Tankut; Gray, Stephen K; Morr, Dirk K; Engel, Gregory S

    2014-03-13

    Long-lived coherences have been observed in photosynthetic complexes after laser excitation, inspiring new theories regarding the extreme quantum efficiency of photosynthetic energy transfer. Whether coherent (ballistic) transport occurs in nature and whether it improves photosynthetic efficiency remain topics of debate. Here, we use a nonequilibrium Green's function analysis to model exciton transport after excitation from an incoherent source (as opposed to coherent laser excitation). We find that even with an incoherent source, the rate of environmental dephasing strongly affects exciton transport efficiency, suggesting that the relationship between dephasing and efficiency is not an artifact of coherent excitation. The Green's function analysis provides a clear view of both the pattern of excitonic fluxes among chromophores and the multidirectionality of energy transfer that is a feature of coherent transport. We see that even in the presence of an incoherent source, transport occurs by qualitatively different mechanisms as dephasing increases. Our approach can be generalized to complex synthetic systems and may provide a new tool for optimizing synthetic light harvesting materials.

  17. Coupled climate model simulations of Mediterranean winter cyclones and large-scale flow patterns

    Directory of Open Access Journals (Sweden)

    B. Ziv

    2013-03-01

    Full Text Available The study aims to evaluate the ability of global, coupled climate models to reproduce the synoptic regime of the Mediterranean Basin. The output of simulations of the 9 models included in the IPCC CMIP3 effort is compared to the NCEP-NCAR reanalyzed data for the period 1961–1990. The study examined the spatial distribution of cyclone occurrence, the mean Mediterranean upper- and lower-level troughs, the inter-annual variation and trend in the occurrence of