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RECIRCULATING FLOW IN SHALLOW OPEN CHANNEL via THE RNG κ-ε MODEL 被引量:2
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作者 Kuang Cui-ping (Department of River & Harbour Engineering, Nanjing Hydraulic Research Institute, Nanjing 210024, P. R. China ) 《Journal of Hydrodynamics》 SCIE EI CSCD 1999年第1期41-49,共9页
The steady recirculating flow behind a sudden expansion in a shallow channel is studied using the renormalization group (RNG) κ-ε model. The predicted recirculating flow and the reattachment length of the recircula... The steady recirculating flow behind a sudden expansion in a shallow channel is studied using the renormalization group (RNG) κ-ε model. The predicted recirculating flow and the reattachment length of the recirculating flow are well-supported by the reported experimental data. The computed effective viscosity, turbulence kinetic energy and its dissipation rate given by the RNG κ-ε model are smaller than that by the standard κ-ε model, while the reattachment length of the recirculating flow is larger. The RNG κ-ε medel overcomes the shortcoming of underpredicting the length of the recirculation zone by the standard κ-ε model. 展开更多
关键词 open channel RNG κ-ε recirculating flow
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EXPERIMENTAL STUDIES ON SWIRLING AND RECIRCULATING TWO-PHASE FLOW FIELD IN A COLD MODEL OF DUAL-INLET SUDDEN-EXPANSION COMBUSTOR 被引量:1
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作者 周力行 李荣先 廖昌明 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2000年第4期193-197,共5页
The axial and tangential velocities of gas and particle phases and particle concentration for turbulent swirling and recirculating gas-particle (simulating gas-droplet) flows in a cold model of a dual-inlet sudden-exp... The axial and tangential velocities of gas and particle phases and particle concentration for turbulent swirling and recirculating gas-particle (simulating gas-droplet) flows in a cold model of a dual-inlet sudden-expansion combustor with partially tangential central tubes, proposed by the present authors, were measured by using a 2-D LDV system and a laser optic fiber system combined with a sampling probe. The results show that there are both gas and particle strongly reverse flows and swirling flows in the head part of the combustor. The velocity slip between gas and particle phases is remarkable. The particle concentration is higher near the wall and lower near the axis. There are two peaks in the concentration profiles near the inlet tubes. The above-obtained flow characteristics are favorable to ignition, flame stabilization and combustion. The results can also be used to validate the numerical modeling. 展开更多
关键词 swirling and recirculating flows gas-particle flows sudden-expansion combustor LDV measurements experimental studies
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A one-equation turbulence model for recirculating flows 被引量:3
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作者 Yang Zhang Jun Qiang Bai +1 位作者 Jing Lei Xu Yi Li 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2016年第6期77-88,共12页
A one-equation turbulence model which relies on the turbulent kinetic energy transport equation has been developed to predict the flow properties of the recirculating flows. The turbulent eddy-viscosity coefficient is... A one-equation turbulence model which relies on the turbulent kinetic energy transport equation has been developed to predict the flow properties of the recirculating flows. The turbulent eddy-viscosity coefficient is computed from a recalibrated Bradshaw's assumption that the constant a1= 0.31 is recalibrated to a function based on a set of direct numerical simulation(DNS) data. The values of dissipation of turbulent kinetic energy consist of the near-wall part and isotropic part, and the isotropic part involves the von Karman length scale as the turbulent length scale. The performance of the new model is evaluated by the results from DNS for fully developed turbulence channel flow with a wide range of Reynolds numbers. However, the computed result of the recirculating flow at the separated bubble of NACA4412 demonstrates that an increase is needed on the turbulent dissipation, and this leads to an advanced tuning on the self-adjusted function. The improved model predicts better results in both the non-equilibrium and equilibrium flows, e.g. channel flows, backward-facing step flow and hump in a channel. 展开更多
关键词 turbulent flows one-equation turbulence model recirculating flows
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THE APPLICATION AND DEVELOPMENT OF TURBULENCE MODELS IN BUOYANT RECIRCULATING FLOWS
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作者 Ni Hao-qing, Institute of Water Conservancy and Hydroelectric Power Research, Beijing 100044, P.R.China 《Journal of Hydrodynamics》 SCIE EI CSCD 1991年第2期58-70,共13页
In this paper, a modified κ-ε turbulence model, a simplified algebraic stress model and a developed two-fluid model have been presented based on numerical modeling of turbulent buoyant recirculating flows. The calcu... In this paper, a modified κ-ε turbulence model, a simplified algebraic stress model and a developed two-fluid model have been presented based on numerical modeling of turbulent buoyant recirculating flows. The calculated results by these models are in good agreement with experiments. However, the last model is much better for simulating gravity-stratified flows. 展开更多
关键词 THE APPLICATION AND DEVELOPMENT OF TURBULENCE MODELS IN BUOYANT recirculating flowS CHEN ACFM NI
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Impact of an artificial chute cutoff on the river morphology and flow structure in Sipaikou area of the Upper Yellow River 被引量:3
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作者 QIAO Qiao Li Chun-guang +2 位作者 JING He-fang HUANG Ling-xiao YANG Cheng 《Journal of Mountain Science》 SCIE CSCD 2021年第12期3275-3290,共16页
Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which ma... Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which makes it difficult to study the interaction between river morphology and flow structure only through field measurement.However,numerical simulations can provide insights into the hydrodynamic characteristics after artificial chute cutoffs.In this study,both field measurement and numerical simulation are employed to investigate the flow structure and bed morphology caused by an artificial chute cutoff in Sipaikou area of the Upper Yellow River in 2018.The measured hydrological data provide boundary conditions and initial values for the numerical model.The field measurement results reveal that the concave bank of the study area is severely scoured up to 270 m after the artificial cutoff,and a 20 m deep scour hole and a 2.26 km long pool are formed at the entrance and near the left bank of the chute channel.The numerical simulation results of velocity at typical cross-sections are in good agreement with the measurement results.Flow separation and stagnation zones are observed near the right bank during the low flow conditions(discharge of at least 902 m^(3)/s),but this phenomenon is not seen during larger flow conditions(discharge exceeds 2000 m^(3)/s).Interestingly,flow recirculation zones are also found near the left and right banks of the scour hole.Further,a long flux belt is formed at the scour hole and the pool.Consequently,the impact of the bed topography on the hydrodynamic characteristics is relatively prominent when the discharge is small,while the impact on the river banks and river bed is more noticeable when the water discharge is large.In addition,high shear stress is observed near the left bank at the downstream of the studied area,which indicates that the left bank at the downstream is still being scoured.These results suggest that bank protection measures along the left bank are required to maintain the effectiveness of the artificial chute cutoff. 展开更多
关键词 Artificial chute cutoff flow recirculation HYDRODYNAMIC Scour hole Yellow River
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Anoxic Biological Phosphorus Uptake in A^2O Process 被引量:10
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作者 WANG Xiaolian(王晓莲) +3 位作者 WANG Shuying(王淑莹) PENG Yongzhen(彭永臻) 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2005年第4期516-521,共6页
A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (D... A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen (92.3%, 95.5%, 96% and 79.5%, respectively) could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation. 展开更多
关键词 A^2O process nitrogen and phosphorus removal denitrifying phosphorus removing bacteria nitrate recirculation flow
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Transient behaviors of a flame over a Tsuji burner
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作者 Young-Da Chen Da-Da Chen Chiun-Hsun Chen 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2008年第6期645-659,共15页
The present study investigated numerically the physical mechanisms underlying the transient behaviors of the flame over a porous cylindrical burner. The numerical results showed that a cold flow structure at a fixed i... The present study investigated numerically the physical mechanisms underlying the transient behaviors of the flame over a porous cylindrical burner. The numerical results showed that a cold flow structure at a fixed inflow velocity of Uin = 0.6 m/s in a wind tunnel could be observed in two co-existing recirculation flows. Flow variations occur repeatedly until t = 4.71 s, and then a vortex existed steadily behind the burner and no shading occurred. The ignition of flammable mixture led to a rapid rise in gas temperature and a sudden gas expansion. When it reached the stable envelope flame condition, Uin is adjusted to an assigned value. Two blow-off mechanisms were identified. It was also found in the study flame shapes with buoyancy effects agreed with the ones observed experimentally by Tsai. Furthermore, the lift-off flame would appear briefly between the envelopes and wake ones, and was stabilized as a wake flame. 展开更多
关键词 Tsuji burner Lift-off flame Recirculation flow
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Numerical Study of the Feed Flow and Its Influence on the Separation Efficiency of a Gas Centrifuge 被引量:2
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作者 傅瑞峰 陈伟波 应纯同 《Tsinghua Science and Technology》 SCIE EI CAS 1996年第1期61-65,共5页
In a Zippe-type 3-pole gas centrifuge, feed gas is introduced through a sonic nozzle into the rarefied region in the rotor. Introduction of the nonrotating feed gas will slow the whirl flow and introduce a secondary r... In a Zippe-type 3-pole gas centrifuge, feed gas is introduced through a sonic nozzle into the rarefied region in the rotor. Introduction of the nonrotating feed gas will slow the whirl flow and introduce a secondary recirculating flow in the meridian plane. The effects of feed gas on the output of a gas centrifuge are investigated. The non-linear. axisymmetric N-S equations are used to calculate the secondary flow induced by the feed gas. Three types of numerical schemes. an implicit scheme similar to the Beam-Warming scheme. an implicit unfactorized scheme and an improved Newton-Raphson scheme are used. The Cohen separation theory with axial variation is used forcalculating the isotope concentration. Optimization of the output is achieved by automatic variation of the weighting factors for a number of linear flow solutions which can be superimposed. A Rome type centrifuge is analyzed as an example. Results show the recirculating flow caused by the feed gas. especially the acceleration loss. has an important effect on the output of a gas centrifuge. 展开更多
关键词 feed flow: Navier-Stokes equations separation efficiency gas centrifuge secondary recirculating flow
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Investigation on Inlet Recirculation Characteristics of Double Suction Centrifugal Compressor with Unsymmetrical Inlet 被引量:1
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作者 YANG Ce WANG Yingjun +3 位作者 LAO Dazhong TONG Ding WEI Longyu LIU Yixiong 《Journal of Thermal Science》 SCIE EI CAS CSCD 2016年第4期312-324,共13页
The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method,mainly focused on three issues including the amounts and difference... The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method,mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions,the circumferential non-uniform distributions of the inlet recirculation,the recirculation velocity distributions of the upstream slot of the rear impeller.The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions..In design speed,the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range,but in the small flow range,the recirculation flow rate of the rear impeller is smaller than that of the front impeller.In different working conditions,the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different.The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change.The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller,but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller,the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute.In the design flow and small flow conditions,the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different,and the recirculation velocities distribution forms at both sides of the mean line are different.The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct. 展开更多
关键词 asymmetric intake double suction centrifugal compressor inlet recirculation recirculation flow circumferential distribution
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