The wall-adapting local eddy-viscosity(WALE)and Vreman subgrid scale models for large eddy simulations are compared within the framework of a generalised lattice Boltzmann method.Fully developed turbulent flows near a...The wall-adapting local eddy-viscosity(WALE)and Vreman subgrid scale models for large eddy simulations are compared within the framework of a generalised lattice Boltzmann method.Fully developed turbulent flows near a flat wall are simulated with the two models for the shear(or friction)Reynolds number of 183.6.Compared to the direct numerical simulation(DNS),damped eddy viscosity in the vicinity of the wall and a correct velocity profile in the transitional region are achieved by both the models without dynamic procedures.The turbulent statistics,including,e.g.,root-mean-square velocity fluctuations,also agree well with the DNS results.The comparison also shows that the WALE model predicts excellent damped eddy viscosity near the wall.展开更多
We present a systematic derivation of a model based on the central moment lattice Boltzmann equation that rigorously maintains Galilean invariance of forces to simulate inertial frame independent flow fields.In this r...We present a systematic derivation of a model based on the central moment lattice Boltzmann equation that rigorously maintains Galilean invariance of forces to simulate inertial frame independent flow fields.In this regard,the central moments,i.e.moments shifted by the local fluid velocity,of the discrete source terms of the lattice Boltzmann equation are obtained by matching those of the continuous full Boltzmann equation of various orders.This results in an exact hierarchical identity between the centralmoments of the source terms of a given order and the components of the central moments of the distribution functions and sources of lower orders.The corresponding source terms in velocity space are then obtained from an exact inverse transformation due to a suitable choice of orthogonal basis for moments.Furthermore,such a central moment based kinetic model is further extended by incorporating reduced compressibility effects to represent incompressible flow.Moreover,the description and simulation of fluid turbulence for full or any subset of scales or their averaged behavior should remain independent of any inertial frame of reference.Thus,based on the above formulation,a new approach in lattice Boltzmann framework to incorporate turbulence models for simulation of Galilean invariant statistical averaged or filtered turbulent fluid motion is discussed.展开更多
基金Supported by the Research Fund for the Doctoral Program of Higher Education of China,the National Natural Science Foundation of China under Grant Nos 10902087,11172241the National Hi-Tech Research and Development Program of China under Grant No 2012AA011803.
文摘The wall-adapting local eddy-viscosity(WALE)and Vreman subgrid scale models for large eddy simulations are compared within the framework of a generalised lattice Boltzmann method.Fully developed turbulent flows near a flat wall are simulated with the two models for the shear(or friction)Reynolds number of 183.6.Compared to the direct numerical simulation(DNS),damped eddy viscosity in the vicinity of the wall and a correct velocity profile in the transitional region are achieved by both the models without dynamic procedures.The turbulent statistics,including,e.g.,root-mean-square velocity fluctuations,also agree well with the DNS results.The comparison also shows that the WALE model predicts excellent damped eddy viscosity near the wall.
文摘We present a systematic derivation of a model based on the central moment lattice Boltzmann equation that rigorously maintains Galilean invariance of forces to simulate inertial frame independent flow fields.In this regard,the central moments,i.e.moments shifted by the local fluid velocity,of the discrete source terms of the lattice Boltzmann equation are obtained by matching those of the continuous full Boltzmann equation of various orders.This results in an exact hierarchical identity between the centralmoments of the source terms of a given order and the components of the central moments of the distribution functions and sources of lower orders.The corresponding source terms in velocity space are then obtained from an exact inverse transformation due to a suitable choice of orthogonal basis for moments.Furthermore,such a central moment based kinetic model is further extended by incorporating reduced compressibility effects to represent incompressible flow.Moreover,the description and simulation of fluid turbulence for full or any subset of scales or their averaged behavior should remain independent of any inertial frame of reference.Thus,based on the above formulation,a new approach in lattice Boltzmann framework to incorporate turbulence models for simulation of Galilean invariant statistical averaged or filtered turbulent fluid motion is discussed.
