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Abstract
In this work, we have theoretically analyzed and numerically evaluated the accuracy of highorder lattice Boltzmann (LB) models for capturing nonequilibrium effects in rarefied gas flows. In the incompressible limit, the LB equation is shown to be able to reduce to the linearized Bhatnagar–Gross–Krook (BGK) equation. Therefore, when the same Gauss–Hermite quadrature is used, LB method closely resembles the discrete velocity method (DVM). In addition, the order of Hermite expansion for the equilibrium distribution function is found not to be directly correlated with the approximation order in terms of the Knudsen number to the BGK equation for incompressible flows. Meanwhile, we have numerically evaluated the LB models for a standingshearwave problem, which is designed specifically for assessing model accuracy by excluding the influence of gas molecule/surface interactions at wall boundaries. The numerical simulation results confirm that the highorder terms in the discrete equilibrium distribution function play a negligible role in capturing nonequilibrium effect for lowspeed flows. By contrast, appropriate Gauss–Hermite quadrature has the most significant effect on whether LB models can describe the essential flow physics of rarefied gas accurately. Our simulation results, where the effect of wall/gas interactions is excluded, can lead to conclusion on the LB modeling
capability that the models with higherorder quadratures provide more accurate results. For the same order Gauss–Hermite quadrature, the exact abscissae will also modestly influence numerical accuracy. Using the same Gauss–Hermite quadrature, the numerical results of both LB and DVM methods are in excellent agreement for flows across a broad range of the Knudsen numbers, which confirms that the LB simulation is similar to the DVM process. Therefore, LB method can offer flexible models suitable for simulating continuum flows at the Navier–Stokes level and rarefied gas flows at the linearized Boltzmann model equation level.
capability that the models with higherorder quadratures provide more accurate results. For the same order Gauss–Hermite quadrature, the exact abscissae will also modestly influence numerical accuracy. Using the same Gauss–Hermite quadrature, the numerical results of both LB and DVM methods are in excellent agreement for flows across a broad range of the Knudsen numbers, which confirms that the LB simulation is similar to the DVM process. Therefore, LB method can offer flexible models suitable for simulating continuum flows at the Navier–Stokes level and rarefied gas flows at the linearized Boltzmann model equation level.
Original language  English 

Pages (fromto)  835849 
Number of pages  15 
Journal  Journal of Computational Physics 
Volume  230 
Issue number  3 
DOIs  
Publication status  Published  1 Feb 2011 
Keywords
 lattice Boltzmann (LB) models
 rarefied gas flows
 standingshearwave problem
 simulating continuum flows
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Projects
 1 Finished

Novel multirelaxation time order models for Lattice Bolztman Simulation of Gas Flows
Zhang, Y.
EPSRC (Engineering and Physical Sciences Research Council)
1/03/08 → 28/02/11
Project: Research