This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method （LBM） and Modified Moment Propagation （MMP） method, and this mixed method is proved to have se...This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method （LBM） and Modified Moment Propagation （MMP） method, and this mixed method is proved to have several advantages over the LBM and Moment Propagation （MP） mixed method which leads to negative concentrations under some conditions in computation. The disadvantage of LBM/MP has been overcome to a certain extent. Also, this work presents an LBM solution of modeling single fractures with uniformly or randomly distributed grains, which can provide a new path of applying the LBM in solute transport simulation in fractures.展开更多
A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows...A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows in a pumping-station forebay.Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation（LES） model.The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary,the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions.Firstly,the model successfully predicts the flow characteristics around a spur dike,such as circulating flow,velocity and water depth distributions.The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model（SM） of LES.Finally,the LBM-SGS model is used to further predict the flow characteristics in a forebay,such as secondary flow and water level.The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.展开更多
A single-phase free surface tracking model based on the Lattice Boltzmann Method （LBM）, which has capability of simulating liquid-gas system with the assumption that the gas phase has only negligible influence on th...A single-phase free surface tracking model based on the Lattice Boltzmann Method （LBM）, which has capability of simulating liquid-gas system with the assumption that the gas phase has only negligible influence on the liquid phase, is utilized to simulate the flow of a drop impacting on a liquid film. Three typical outcomes in the flows, i.e., deposition, crown and splash, which have been observed in the previous experiments, are obtained in the present three dimensional numerical simulations. The numerical results are consistent with the experimental and analytical results available.展开更多
The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, fl...The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, flow regimes under different wall wettabilities are investigated. Because of the wall wettability, liquid apparent slip is observed. Slip lengths for different wall wettabilities are found to collapse nearly onto a single curve as a function of the static contact angle, and thereby a relationship between apparent slip length and contact angle is suggested. Our results also show that the wall wettability leads to the formation of a low-density layer between solid wall and liquid, which produced apparent slip in the micro-scale.展开更多
The lattice Boltzmann method （LBM） is used to examine free convection of nanofluids. The space between the cold outer square and heated inner circular cylinders is filled with water including various kinds of nanopa...The lattice Boltzmann method （LBM） is used to examine free convection of nanofluids. The space between the cold outer square and heated inner circular cylinders is filled with water including various kinds of nanoparticles： TiO2, Ag, Cu, and A1203. The Brinkman and Maxwell-Garnetts models are used to simulate the viscosity and the effective thermal conductivity of nanofluids, respectively. Results from the performed numerical analysis show good agreement with those obtained from other numerical meth- ods. A variety of the Rayleigh number, the nanoparticle volume fraction, and the aspect ratio are examined. According to the results, choosing copper as the nanoparticle leads to obtaining the highest enhancement for this problem. The results also indicate that the maximum value of enhancement occurs at λ =2.5 when Ra = 106 while at A = 1.5 for other Rayleigh numbers.展开更多
The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for study...The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for studying the underlying mechanisms and for controlling the adverse effects. To develop an effective and efficient method for simulation of temporal and spatial temperature variations, a lattice Boltzmann method（LBM） model for 3-D thermal buoyancy flows is proposed and validated by the temperature data measured in a model reservoir. This paper discusses important aspects of the LBM and its turbulence model, analyzes the gravity sinking mechanism of cold currents, and demonstrates the complexity of the temperature redistribution process. Good agreement between the simulated and measured results shows that the newly developed method is feasible and powerful, and it will be used for the water temperature prediction in actual reservoirs in a near future.展开更多
The settling and hydrodynamic properties of 3-D fractal flocs in quiescent water are investigated with a numerical model based on the Lattice Boltzmann Method （LBM）, with considering the settling velocity, hydrodyna...The settling and hydrodynamic properties of 3-D fractal flocs in quiescent water are investigated with a numerical model based on the Lattice Boltzmann Method （LBM）, with considering the settling velocity, hydrodynamic drag force and infra-floc flow. The comparisons of floc settling velocities and effective densities indicate that the numerical results present good agreements with observations in field and at laboratory. The results show that the drag force Fo increases with the floc size dr according to the relationship FD ∝ df^3. Moreover, the intra-floc flow field and movement of the pore water provide a better understanding of the intra-floc flow from the microscopic viewpoint. The results also indicate that the lattice Boltzmann method is a promising approach to reveal the mechanisms of the flocculation in aquatic environments.展开更多
The Lattice Boltzmann Method （LBM） was investigated to solve triangular cavity flow and free-surface problems in hydraulic dynamics. Some cases of triangular cavity flow and backward step flow were simulated to show...The Lattice Boltzmann Method （LBM） was investigated to solve triangular cavity flow and free-surface problems in hydraulic dynamics. Some cases of triangular cavity flow and backward step flow were simulated to show the efficiency and stability of this method. Two-dimensional partial dam breaking problem and the propagation and diffraction of dam-break wave around rectangular and circular cylinder were numerically studied successfully. Excellent agreement was obtained between numerical predictions and available results.展开更多
Aerodynamic simulation of high-speed trains has been carried out by using Lattice Boltzmann Method (LBM). Non-simplified train model was used and the number of space grids reached tens of millions. All results under d...Aerodynamic simulation of high-speed trains has been carried out by using Lattice Boltzmann Method (LBM). Non-simplified train model was used and the number of space grids reached tens of millions. All results under different working conditions reflected the actual situation.展开更多
Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation ...Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation data shows that wind gust structure has coherent characteristics.This is important for entrainment of spring dust storms into the upper boundary layer,where they are transported great distances.The Lattice Boltzmann Method(LBM) is a computational fluid technique based on the Boltzmann transport equation.The LBM has been used to study complex motion such as turbulence,because it describes motion at the micro level.In this paper,Large eddy simulation is introduced in the LBM,enabling simulation of turbulent flow in the atmospheric boundary layer.The formation and development of wind gusts are simulated,and a coherent structure with a combination of wave and vortex is obtained.This explains the mechanism of soil erosion and sand entrainment by the coherent structure of wind gusts.展开更多
Many-core processors, such as graphic processing units (GPUs), are promising platforms for intrinsic parallel algorithms such as the lattice Boltzmann method (LBM). Although tremendous speedup has been obtained on a s...Many-core processors, such as graphic processing units (GPUs), are promising platforms for intrinsic parallel algorithms such as the lattice Boltzmann method (LBM). Although tremendous speedup has been obtained on a single GPU compared with mainstream CPUs, the performance of the LBM for multiple GPUs has not been studied extensively and systematically. In this article, we carry out LBM simulation on a GPU cluster with many nodes, each having multiple Fermi GPUs. Asynchronous execution with CUDA stream functions, OpenMP and non-blocking MPI communication are incorporated to improve efficiency. The algorithm is tested for two-dimensional Couette flow and the results are in good agreement with the analytical solution. For both the oneand two-dimensional decomposition of space, the algorithm performs well as most of the communication time is hidden. Direct numerical simulation of a two-dimensional gas-solid suspension containing more than one million solid particles and one billion gas lattice cells demonstrates the potential of this algorithm in large-scale engineering applications. The algorithm can be directly extended to the three-dimensional decomposition of space and other modeling methods including explicit grid-based methods.展开更多
Multi-Relaxation-Time Lattice Boltzmann Method （MRT LBM） is of better numerical stability and has attracted more and more research interests. The previous MRT LBM included artificial compressible effects. To overcom...Multi-Relaxation-Time Lattice Boltzmann Method （MRT LBM） is of better numerical stability and has attracted more and more research interests. The previous MRT LBM included artificial compressible effects. To overcome the disadvantage, an incompressible MRT LBM has been proposed in two dimensions recently. In this article, we present incompressible MRT LBMs in 3-D space, with example of nineteen-velocity. The equilibria in momentum space are derived from an earlier incompressible Lattice Bhatnagar-Gross-Krook （LBGK） model proposed by Guo et al.. Through the Chapman-Enskog （C-E） expansion, the incompressible Navier-Stokes （N-S） equations can be recovered without artificial compressible effects. Simulations of a lid-driven cavity flow in three dimensions with Re = 1 000, 2 000 and 3 200 are performed. The simulation results agree with the existing data and clearly demonstrate better numerical stability of the presented model over the incompressible LBGK model.展开更多
基金the National Natural Science Foundation of China (Grant No. 50579012)
文摘This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method （LBM） and Modified Moment Propagation （MMP） method, and this mixed method is proved to have several advantages over the LBM and Moment Propagation （MP） mixed method which leads to negative concentrations under some conditions in computation. The disadvantage of LBM/MP has been overcome to a certain extent. Also, this work presents an LBM solution of modeling single fractures with uniformly or randomly distributed grains, which can provide a new path of applying the LBM in solute transport simulation in fractures.
基金supported by the National Natural Science Foundation of China (Grant No. 50779069)the Beijing Natural Science Foundation (Grant No. 3083022)+3 种基金the Open Fund of Key Laboratory of Yellow River Sediment Research of the Ministry of Water Resources (Grant No. 200903)the National Science and Technology Supporting Programs in the 11th Five-Year Plan (Grant No. 2006BAB06B02)the Chinese Universities Scientific Fund (Grant Nos. 2009-1-90, 2009-2-12)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. PCSIRT0657)
文摘A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows in a pumping-station forebay.Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation（LES） model.The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary,the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions.Firstly,the model successfully predicts the flow characteristics around a spur dike,such as circulating flow,velocity and water depth distributions.The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model（SM） of LES.Finally,the LBM-SGS model is used to further predict the flow characteristics in a forebay,such as secondary flow and water level.The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.
基金the National Natural Science Foundation of China (Grant No. 10472062)the Special Scientific Foundation for Selection and Cultivation of Excellent Young Scholars in Shanghai and the Shanghai Leading Academic Discipline Project (Grant No.Y0103)
文摘A single-phase free surface tracking model based on the Lattice Boltzmann Method （LBM）, which has capability of simulating liquid-gas system with the assumption that the gas phase has only negligible influence on the liquid phase, is utilized to simulate the flow of a drop impacting on a liquid film. Three typical outcomes in the flows, i.e., deposition, crown and splash, which have been observed in the previous experiments, are obtained in the present three dimensional numerical simulations. The numerical results are consistent with the experimental and analytical results available.
基金the National Natural Science Foundation of China (Grant No. 50874071)the National High Technology Research and Development of China (863 Program,Grant No. 2008AA06Z201)+1 种基金the Key Program of Science and Technology Commission of Shanghai Municipality (Grant No.071605102)the Leading Talent Funding of Shanghai
文摘The apparent slip between solid wall and liquid is studied by using the Lattice Boltzmann Method （LBM） and the Shan-Chen multiphase model in this paper. With a no-slip bounce-back scheme applied to the interface, flow regimes under different wall wettabilities are investigated. Because of the wall wettability, liquid apparent slip is observed. Slip lengths for different wall wettabilities are found to collapse nearly onto a single curve as a function of the static contact angle, and thereby a relationship between apparent slip length and contact angle is suggested. Our results also show that the wall wettability leads to the formation of a low-density layer between solid wall and liquid, which produced apparent slip in the micro-scale.
文摘The lattice Boltzmann method （LBM） is used to examine free convection of nanofluids. The space between the cold outer square and heated inner circular cylinders is filled with water including various kinds of nanoparticles： TiO2, Ag, Cu, and A1203. The Brinkman and Maxwell-Garnetts models are used to simulate the viscosity and the effective thermal conductivity of nanofluids, respectively. Results from the performed numerical analysis show good agreement with those obtained from other numerical meth- ods. A variety of the Rayleigh number, the nanoparticle volume fraction, and the aspect ratio are examined. According to the results, choosing copper as the nanoparticle leads to obtaining the highest enhancement for this problem. The results also indicate that the maximum value of enhancement occurs at λ =2.5 when Ra = 106 while at A = 1.5 for other Rayleigh numbers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10572106,10872153 and 11172219)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130141110013)
文摘The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for studying the underlying mechanisms and for controlling the adverse effects. To develop an effective and efficient method for simulation of temporal and spatial temperature variations, a lattice Boltzmann method（LBM） model for 3-D thermal buoyancy flows is proposed and validated by the temperature data measured in a model reservoir. This paper discusses important aspects of the LBM and its turbulence model, analyzes the gravity sinking mechanism of cold currents, and demonstrates the complexity of the temperature redistribution process. Good agreement between the simulated and measured results shows that the newly developed method is feasible and powerful, and it will be used for the water temperature prediction in actual reservoirs in a near future.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50779046, 50279029)
文摘The settling and hydrodynamic properties of 3-D fractal flocs in quiescent water are investigated with a numerical model based on the Lattice Boltzmann Method （LBM）, with considering the settling velocity, hydrodynamic drag force and infra-floc flow. The comparisons of floc settling velocities and effective densities indicate that the numerical results present good agreements with observations in field and at laboratory. The results show that the drag force Fo increases with the floc size dr according to the relationship FD ∝ df^3. Moreover, the intra-floc flow field and movement of the pore water provide a better understanding of the intra-floc flow from the microscopic viewpoint. The results also indicate that the lattice Boltzmann method is a promising approach to reveal the mechanisms of the flocculation in aquatic environments.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10371118, 90411009).
文摘The Lattice Boltzmann Method （LBM） was investigated to solve triangular cavity flow and free-surface problems in hydraulic dynamics. Some cases of triangular cavity flow and backward step flow were simulated to show the efficiency and stability of this method. Two-dimensional partial dam breaking problem and the propagation and diffraction of dam-break wave around rectangular and circular cylinder were numerically studied successfully. Excellent agreement was obtained between numerical predictions and available results.
文摘Aerodynamic simulation of high-speed trains has been carried out by using Lattice Boltzmann Method (LBM). Non-simplified train model was used and the number of space grids reached tens of millions. All results under different working conditions reflected the actual situation.
基金the National Natural Science Foundation of China (40875008)the National Basic Research Program of China (2010CB951804)
文摘Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation data shows that wind gust structure has coherent characteristics.This is important for entrainment of spring dust storms into the upper boundary layer,where they are transported great distances.The Lattice Boltzmann Method(LBM) is a computational fluid technique based on the Boltzmann transport equation.The LBM has been used to study complex motion such as turbulence,because it describes motion at the micro level.In this paper,Large eddy simulation is introduced in the LBM,enabling simulation of turbulent flow in the atmospheric boundary layer.The formation and development of wind gusts are simulated,and a coherent structure with a combination of wave and vortex is obtained.This explains the mechanism of soil erosion and sand entrainment by the coherent structure of wind gusts.
基金supported by the National Natural Science Foundation of China (20221603 and 20906091)
文摘Many-core processors, such as graphic processing units (GPUs), are promising platforms for intrinsic parallel algorithms such as the lattice Boltzmann method (LBM). Although tremendous speedup has been obtained on a single GPU compared with mainstream CPUs, the performance of the LBM for multiple GPUs has not been studied extensively and systematically. In this article, we carry out LBM simulation on a GPU cluster with many nodes, each having multiple Fermi GPUs. Asynchronous execution with CUDA stream functions, OpenMP and non-blocking MPI communication are incorporated to improve efficiency. The algorithm is tested for two-dimensional Couette flow and the results are in good agreement with the analytical solution. For both the oneand two-dimensional decomposition of space, the algorithm performs well as most of the communication time is hidden. Direct numerical simulation of a two-dimensional gas-solid suspension containing more than one million solid particles and one billion gas lattice cells demonstrates the potential of this algorithm in large-scale engineering applications. The algorithm can be directly extended to the three-dimensional decomposition of space and other modeling methods including explicit grid-based methods.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 70271609,11026181)
文摘Multi-Relaxation-Time Lattice Boltzmann Method （MRT LBM） is of better numerical stability and has attracted more and more research interests. The previous MRT LBM included artificial compressible effects. To overcome the disadvantage, an incompressible MRT LBM has been proposed in two dimensions recently. In this article, we present incompressible MRT LBMs in 3-D space, with example of nineteen-velocity. The equilibria in momentum space are derived from an earlier incompressible Lattice Bhatnagar-Gross-Krook （LBGK） model proposed by Guo et al.. Through the Chapman-Enskog （C-E） expansion, the incompressible Navier-Stokes （N-S） equations can be recovered without artificial compressible effects. Simulations of a lid-driven cavity flow in three dimensions with Re = 1 000, 2 000 and 3 200 are performed. The simulation results agree with the existing data and clearly demonstrate better numerical stability of the presented model over the incompressible LBGK model.
