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| 1 | Large eddy simulation of flow in a street canyon with tree planting under various atmospheric instability conditions显示文摘In this work, a large eddy simulation (LES) model, which includes momentum and heat source (or sink) inside the tree planting layer, is proposed for the simulation of flow in a street canyon with tree planting. Vegetation canopy layer simulation shows that this model can be used to simulate the velocity distribution and temperature variation inside the canopy layer. Effects of atmospheric instability on flow and pollutant distribution in a street canyon with tree planting of an aspect ratio of 0.5 are studied. Results show that compared with the canyon with no tree planting (or the exposed street canyon), the canyon with tree planting shows a reduced wind circulation and pollutant exchange rate (PER) at the top layer of the street canyon, which induces the increase in the pollutant concentrations near road surface, leeward wall and windward wall. When street canyon atmosphere is under a strongly unstable condition, wind velocity decreases while pollutant concentration is increased in the areas near the street canyon top, road surface, leeward and windward walls, compared with the wind velocity in the street canyon with the neutral stratification. When street canyon atmosphere is under a weakly unstable condition, wind velocity weakens near the street canyon top and windward wall, but strengthens near the road surface and leeward wall, and pollutant concentration is decreased near the leeward and windward walls and is increased between the two rows of trees. When the street canyon atmosphere is under an unstable condition, PER is lower than that under the neutral stratification. | GU ZhaoLin1, ZHANG YunWei2 & LEI KangBin3 1 School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China 1 School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China 3 RIKEN Institute, Wako, Saitama, 351-0198, Japan | 2010 | Science China(Technological Sciences)2010，53，7： | 10 |
| 2 | Modeling of Motion of Particle Clouds Formed by Dumping Dredged Material显示文摘The motion of particle clouds formed by dumping dredged material into quiescent waters is experimentally and numerically studied. In the numerical model, the particle phase is modeled by the dispersion model, and turbulence is calculated by the large eddy simulation. The governing equations, including the filtered Navier-Stokes equations and mass transport equation, are solved based on the operator-splitting algorithm and an implicit cubic spline interpolation scheme. The eddy viscosity is evaluated by the modified Smagorinsky model including the buoyancy term. Comparisons of main flow characteristics, including shape, size, average density excess, moving speed and the amount of particles deposited on the bed, between experimental and computational results show that the numerical model well predicts the motion of the cloud from the falling to spreading stage. The effects of silt-fence on the motion of the particle cloud are also investigated. | 应新亚 JuichiroAKIYAMA 毛根海 | 2001 | China Ocean Engineering2001，16，1： | 8 |
| 3 | Hybrid CFD/FEM-BEM simulation of cabin aerodynamic noise for vehicles traveling at high speed显示文摘Flow passing a vehicle may lead to the increase of the cabin interior noise level through a variety of mechanisms. These mechanisms include vibrations caused by aerodynamic excitations and reradiation from the glass panels, exterior noise trans-mitted and leaked through door seals including gaps and glass edge, and transmission of airborne noise generated by the interaction of flow with body panels. It is of vital importance to predict both the flow fields and the acoustic sources around the ve-hicle to accurately assess the impact of wind induced noise inside the cabin. In the present study, an unstructured segregated finite volume model was used to calculate the flow fields in which a hexahedron grid is used to simplify the vehicle geometry.A large eddy simulation coupled with a wall function model was applied to predict the exterior transient flow fields. The mean flow quantities were thus calculated along the symmetry plane and the vehicle's side windows. A coupled FEM/BEM method was used to compute the vehicle's interior noise level. The total contribution of the interior noise level due to the body panels of the vehicle was subsequently analyzed. | WANG YiPing ZHEN Xin WU Jing GU ZhengQi XIAO ZhenYi YANG Xue | 2013 | Science China(Technological Sciences)2013，56，7： | 7 |
| 4 | 3-D NUMERICAL SIMULATION OF FLOW THROUGH AN ORIFICE SPILLWAY TUNNEL显示文摘A Large Eddy Simulation (LES) approach based on the weakly compressible hydrodynamic equation with a single plase fluid model for the cavitation flow has been developed and employed in simulating 3 D unsteady viscous flow through an orifice type spillwy tunnel. The finite volume approach in space and the predictor corrector method in time have been used to the numerical discretization, and the 'Law of wall' is applied at the solid boundary. The velocity, pressure fields and the cavitation phenomenon are obtained, the computational results show that 3 D LES approach can give more realistic flow field prediction of the orifice type spillway tunnel. | Zhang Chang bing, Yang Yong quan Hydraulics and Hydroelectric Engineering College, Sichuan University, Chengdu 610065, China | 2002 | Journal of Hydrodynamics2002，14，3： | 6 |
| 5 | Numerical simulation of flow separation over a backward-facing step with high Reynolds number显示文摘Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices.In this study,LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS).The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS).This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of 2.00.The results indicate that the LES model can reveal largescale vortex motion although with a larger grid-cell size.However,the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine grid.Overall,LES is a potential tool for simulating separated flow controlled by large-scale vortices. | Fang-fang Wang Shi-qiang Wu Sen-lin Zhu | 2019 | Water Science and Engineering2019，12，2： | 5 |
| 6 | Large Eddy Simulation of a dilute particleladen turbulent flow over a backwardfacing step显示文摘Dilute gas-particle turbulent flows over a backward-facing step are numerically simulated by Large Eddy Simulation (LES) for the continuous phase and Lagran- gian particle trajectory method for the particle phase. Predicted results of mean velocities and fluctuating velocities of both phases agree well with the experimental data, and demonstrate that the main characteristics of the flow are accurately captured by the simulations. Characteristics of separation and reattachments as well as essential features of the coherent structure are obtained, in which the processes of vortex roll up, growth, pairing and breaking up are shown in details. Particle dispersions are then investigated through particles’ instantaneous distri- butions in coherent structure as well as the mean and fluctuating properties of particle number density (PND). The predicted mean PND agree well with experiment results. For small particles, the instantaneous distributions show much preferential concentration, while their mean PND shows more uniform distribution in down- stream region. On the contrary, for large particles, their instantaneous distributions are much uniform (without clear preferential concentration) due to less effect of large eddy coherent, while their mean PND across the section is not uniform for more particles are distributed in the main flow region. The preferential concentra- tion of particles by the large-scale eddies can lead to a high fluctuating PND. | ZHANG HuiQiang WANG Bing CHAN CheongKi WANG XiLin | 2008 | Science China(Technological Sciences)2008，51，11： | 5 |
| 7 | AN INVESTIGATION OF TURBULENT HEAT TRANSFER IN CHANNEL FLOWS BY LARGE EDDY SIMULATION显示文摘Large Eddy Simulation (LES) of fully developed turbulent channel flow with heat transfer was performed to investigate the effects of the Reynolds number on the turbulence behavior. In the present study, the bottom wall of the channel was cooled and the top wall was heated. The Reynolds numbers, based on the central mean-velocity and the half-width of the channel, were chosen as 4000, 6000, 10 4 and 2×10 4, and the Prandtl number as 1.0. To validate our calculations, the present results were compared with available data obtained by Direct Numerical Simulation (DNS), which proves to be in good agreement with each other. To reveal the effects of the Reynolds number, some typical quantities, including the velocity fluctuations, temperature fluctuation, heat fluxes and turbulent Prandtl number, were studied. | Dong Yu-hong, Zhong Feng-quan, Lu Xi-yun, Zhuang Li-xian Department of Mechanics and Mechanical Engineering, University of Science and Technology of China, Hefei 230026, China | 2002 | Journal of Hydrodynamics2002，14，2： | 4 |
| 8 | LES/FDF simulation of particle dispersion in a gas-particle two phase plane wake flow显示文摘A filtered density function (FDF) transport equation was derived for the fluid velocity seen by the particles in gas-particle two-phase flow. An LES/FDF simulation of a two-phase plane wake flow was carried out. The simulation results were compared with both the experimental photograph and the simulation results without using the FDF model, and proved that the LES/FDF model can clearly improve the spatial dispersion of the particle phase. | JIN HanHui CHEN SuTao CHEN LiHua FAN JianRen | 2009 | Science China(Technological Sciences)2009，52，10： | 4 |
| 9 | Large Eddy Simulation for Plunge Breaker and Sediment Suspension显示文摘Breaking waves are a powerful agent for generating turbulence that plays an important role in many fluid dynamicalprocesses, particularly in the mixing of materials. Breaking waves can dislodge sediment and throw it into suspension,which will then be carried by wave-induced steady current and tidal flow. In order to investigate sediment suspension bybreaking waves, a numerical model based on large-eddy-simulation (LES) is developed. This numerical model can beused to simulate wave breaking and sediment suspension. The model consists of a free-surface model using the surfacemarker method combined with a two-dimensional model that solves the flow equations. The turbulence and the turbulentdiffusion are described by a large-eddy-simulation (LES) method where the large turbulence features are simulated bysolving the flow equations, and a subgrid model represents the small-scale turbulence that is not resolved by the flowmodel. A dynamic eddy viscosity subgrid scale stress model has been used for the present simulation. By applying thismodel to Stokes' wave breaking problem in the surf zone, we find that the model results agree very well with experimentaldata. By use of this model to simulation of the breaking process of a periodic wave, it can be found that the model canreproduce the complicated flow phenomena, especially the plunging breaker. It reflects the dynamic structures of roller orvortex in the plunging breaker, and when the wave breaks, many strong vortex structures will be produced in the innersurf zone where the concentration of suspended sediment can thereby become relatively high. | 白玉川 C.O.NG | 2002 | China Ocean Engineering2002，17，2： | 4 |
| 10 | Effect of Mesoscale Land Use Change on Characteristics of Convective Boundary Layer:Semi-Idealized Large Eddy Simulations over Northwest China显示文摘Although large-scale topography and land use have been properly considered in weather and climate models, the effect of mesoscale and microscale heterogeneous land use on convective boundary layer(CBL) has not been fully understood yet. In this study, the influence of semi-idealized strip-like patches of oases and deserts, which resemble irrigated land use in Northwest China, on the CBL characteristics, is investigated based on the Weather Research and Forecasting(WRF)-large eddy simulation(LES) driven by observed land surface data. The influences of soil water content in oases on aloft CBL flow structure, stability, turbulent kinetic energy(TKE), and vertical fluxes are carefully examined through a group of sensitivity experiments. The results show that secondary circulation(SC)/turbulent organized structures(TOS) is the strongest/weakest when soil water content in oases is close to saturation(e.g.,when the oases are irrigated). With the decrease of soil water content in oases(i.e., after irrigation), SC(TOS) becomes weak(strong) in the lower and middle CBL, the flux induced by SC and TOS becomes small(large), which has a dramatic impact on point measurement of eddy covariance(EC) fluxes. The flux induced by SC and TOS has little influence on EC sensible heat flux, but great influence on EC latent heat flux. Under this circumstance, the area averaged heat flux cannot be represented by point measurement of flux by the EC method, especially just after irrigation in oases. Comparison of imbalance ratio(i.e., contribution of SC and TOS to the total flux) reveals that increased soil moisture in oases leads to a larger imbalance ratio as well as enhanced surface heterogeneity. Moreover,we found that the soil layer configuration at different depths has a negligible impact on the CBL flux properties. | Bangjun CAO Shuwen ZHANG Deqin LI Yanlin LI Linfan ZHOU Jiemin WANG | 2018 | Journal of Meteorological Research2018，32，3： | 4 |
| 11 | Large Eddy Simulation of Liquid Flow in a Stirred Tank with Improved Inner-Outer Iterative Algorithm | 张艳红 杨超 毛在砂 | 2006 | Chinese Journal of Chemical Engineering2006，14，3X： | 4 |
| 12 | Performance of WRF Large Eddy Simulations in Modeling the Convective Boundary Layer over the Taklimakan Desert, China显示文摘The maximum height of the convective boundary layer(CBL)over the Taklimakan Desert can exceed 5000 m during summer and plays a crucial role in the regional circulation and weather.We combined the Weather Research and Forecasting Large Eddy Simulation(WRF-LES)with data from Global Positioning System(GPS)radiosondes and from eddy covariance stations to evaluate the performance of the WRF-LES in simulating the characteristics of the deep CBL over the central Taklimakan Desert.The model reproduced the evolution of the CBL processes reasonably well,but the simulations generated warmer and moister conditions than the observation as a result of the over-prediction of surface fluxes and large-scale advection.Further simulations were performed with multiple configurations and sensitivity tests.The sensitivity tests for the lateral boundary conditions(LBCs)showed that the model results are sensitive to changes in the time resolution and domain size of the specified LBCs.A larger domain size varies the distance of the area of interest from the LBCs and reduces the influence of large forecast errors near the LBCs.Comparing the model results using the original parameterization of sensible heat flux with the Noah land surface scheme and those of the sensitivity experiments showed that the desert CBL is sensitive to the sensible heat flux produced by the land surface scheme during daytime in summer.A reduction in the sensible heat flux can correct overestimates of the potential temperature profile.However,increasing the sensible heat flux significantly reduces the total time needed to increase the CBL to a relatively low altitude(<3 km)in the middle and initial stages of the development of the CBL rather than producing a higher CBL in the later stages. | Hongxiong XU Minzhong WANG Yinjun WANG Wenyue CAI | 2018 | Journal of Meteorological Research2018，32，6： | 3 |
| 13 | Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence显示文摘Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently. | Pedro Xavier Ramos Laurent Schindfessel Joao Pedro Pego Tom De Mulder | 2019 | Water Science and Engineering2019，12，3： | 3 |
| 14 | Numerical investigation of the effect of sub-grid scale eddies on the dispersed particles by LES/FDF model显示文摘An LES/FDF model was developed by the authors to investigate the SGS effect on the particle motion in the gas-particle two-phase plane wake flow.The simulation results of dispersion rate for different particles were compared with the results without using the FDF model.It was shown that the large eddy structure is the dominant factor influencing the particle diffu-sion in space for small particles(small Stokes-number particles),but for intermediate or large diameter particles,the influence of the sub-grid scale eddies on the dispersion rate is in the same order as that of the large eddies.The sub-grid scale eddies increase the particle dispersion rate in most time,but sometimes they decrease the dispersion rate.The sub-grid scale particle dispersion rate is decided not only by the intensity of sub-grid scale eddies and the Stokes number of the particles,but also by the large eddy structure of the flow field.For the particles in isotropic turbulence,the dispersion rate decreases as the particle diameter increases. | JIN HanHui1,CHEN SuTao1,CHEN LiHua1 & FAN JianRen2 1 School of Aeronautics and Astronautics,Zhejiang University,Hangzhou 310027,China 2 State Key Lab of Clean Energy Utilization,Zhejiang University,Hangzhou 310027,China | 2010 | Science China(Technological Sciences)2010，53，5： | 3 |
| 15 | A HYDRODYNAMIC LARGE-EDDY SIMULATION-MODEL USING DIRECTIONAL EDDY VISCOSITY METHOD IN VERTICAL DIRECTION显示文摘A non-linear turbulent hydrodynamic model was proposed by Zhan and Li(1993)using the large eddy simulation approach and directional eddy viscosity method.The model is simplified in this paper and is applied to the problem of a side discharge into open-channel flow,where a reeireulation zone develops downstream of the discharge.The numerical results are compared with experimental results(Strazisar and Prahl(1973)and Mikhail,Chu,and Savage(1975))and previous numerical results obtained using a k-εmodel(McGuirk and Rodi,1978).The agreement is good. | Zhan Jie-minDept. of Applied Mechanics and Engineering, Zhangshan University, Guangzhou 510275,P. R. ChinaY.S.LiDept.of Civil & Structural Engineering, The Hong Kong Polytechnic University, Hong Kong | 1998 | Journal of Hydrodynamics1998，10，1： | 3 |
| 16 | TRANSPORTATION OF PASSIVE SCALAR IN INHOMOGENEOUS TURBULENCE显示文摘The paper studies the transportation of passive scalar in the inho-mogeneous turbulence by means of large eddy simulation.The prediction accuracyis verified by the well-known Comte-Bellot spectrum of the homogeneous turbulence.The mean transportation properties are predicted with satisfaction and the underes-timation of the thermal flux by the phenomenological models has been disclosed.Thehigh intermittence of the temperature fluctuations has been found in the inhomoge-neous turbulence and it is the reason for the underestimation of turbulent thermalflux by the phenomenological model. | 崔桂香 陈宇光 张兆顺 许春晓 L.Shao J.P.Bertoglio | 2000 | Acta Mechanica Sinica2000，16，1： | 3 |
| 17 | Large eddy simulation of a shocked gas cylinder instability induced turbulence显示文摘The Navier-Stokes equations for compressible fluid are solved with the operator splitting technique and LES (large eddy simulation) with the Smagorinsky model. A computational code MVFT (multi-viscosity-fluid and turbulence) is developed to study hydrodynamic instability and the induced turbulent mixing for multi compressible fluid. In order to validate the code MVFT,the LANL's shock tube experiment of shocked SF6 gas cylinder is simulated with the initial state of SF6 gas cylinder described by dissipative ITL (interface transition layer). It is shown that the width and height of gas cylinder calculated with MVFT are closer to the experimental results than RAGE,and that the velocities of upstream edge,downstream edge and vortex edge agree with the experimental results,and are appreciably smaller than the RAGE results. The code MVFT has been pre-liminarily validated. | LI Ping,BAI JingSong,WANG Tao & ZOU LiYong National Key Laboratory for Shock Wave and Detonation Physics Research,Institute of Fluid Physics,CAEP,Mianyang 621900,China | 2010 | Science China(Physics,Mechanics & Astronomy)2010，53，2： | 3 |
| 18 | NUMERICAL SIMULATION OF SEPARATED FLOW NEAR GROYNE显示文摘A numerical model was developed to simulate flow around non-submeged groyne in two dimensions, which was based on N-S equations with Smagorinsky’s subgrid-scale turbulence model. Flow phenomenon and results measured practically agree with the calculation results very well, and this model could be used to simulate the characteristics of the eddies of upper and down reaches around spur-dikes successfully. | Jiang, Chang-Bo Chen, Yong-Kuan Bai, Yu-Chuan Zhao, Zi-Dan | 2002 | Journal of Hydrodynamics2002，14，4： | 2 |
| 19 | Large eddy simulation of stably stratified turbulence显示文摘Stable stratification turbulence, as a common phenomenon in atmospheric and oceanic flows, is an important mechanism for numerical prediction of such flows. In this paper the large eddy simulation is utilized for investigating stable stratification turbulence numerically. The paper is expected to provide correct statistical results in agreement with those measured in the atmosphere or ocean. The fully developed turbulence is obtained in the stable stratification fluid by large eddy simulation with different initial velocity field and characteristic parameters, i.e. Reynolds number Re and Froude number Fr. The evolution of turbulent kinetic energy, characteristic length scales and parameters is analyzed for investigating the development of turbulence in stable stratification fluid. The three-dimensional energy spectra, horizontal and vertical energy spectrum, are compared between numerical simulation and real observation in the atmosphere and ocean in order to test the reliability of the numerical simulation. The results of numerical cases show that the large eddy simulation is capable of predicting the properties of stable stratification turbulence in consistence with real measurements at less computational cost. It has been found in this paper that the turbulence can be developed under different initial velocity conditions and the internal wave energy is dominant in the developed stable stratification turbulence. It is also found that the characteristic parameters must satisfy certain conditions in order to have correct statistical property of stable stratification turbulence in the atmosphere and ocean. The Reynolds number and Froude number are unnecessarily equal to those in atmosphere or ocean, but the Reynolds number must be large enough, say, greater than 10 2 , and Froude number must be less than 0.1. The most important parameter is ReFr 2 which must be greater than 10. | SHEN Zhi, LI YuPeng, CUI GuiXiang & ZHANG ZhaoShun Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China | 2010 | Science China(Physics,Mechanics & Astronomy)2010，53，1： | 2 |
| 20 | NUMERICAL STUDY FOR EVOLUTION OF COHERENT VORTEX IN UNIDIRECTIONAL OSCILLATORY BOUNDARY LAYER OVER SAND RIPPLES显示文摘Ripples are widely formed in river channels and coastal regions, the bed-forms and vortex dynamics accompanied with them are quite important because they are responsible for frictions and sediment transports. The coherent vortex structure play a key role in the process, so how to model them is needed for understanding the formation process of sand ripples. In this paper, 2D Large-Eddy-Simulation (LES) was used to predict the flow structure and the dynamics of coherent vortex. The numerical results show a complete process of formation, evolvement and disappearance for the cases of unidire ctional and oscillatory flows over symmetic and asymmetric | Bai Yu-chuan Institute for Sedimentation on River and Coast Engineering,Tianjin University, Tianjing 300072, China Ng Chiu-On Department of Mechanical Engineering, The University of Hongkong, Hongkong, China | 2002 | Journal of Hydrodynamics2002，14，4： | 2 |
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