复杂微通道气体流动的格子Boltzmann模拟

Lattice Boltzmann simulation of the gas flow in complex microchannels

构建了一个模拟复杂微通道内气体流动的多松弛格子Boltzmann模型。该模型采用动力学曲面滑移边界,考虑了微尺度效应和努森层影响。此外,为了更准确地描述微通道内气体的滑移速度,在模型中引入孔隙局部Kn数来代替平均Kn数。之后采用Poiseuille流对模型进行验证,模拟结果与用直接模拟蒙特卡洛方法和分子模拟结果吻合较好,证明了该模型模拟微通道内处于滑移区和过渡区气体流动的有效性。最后,采用该模型模拟多孔介质内气体渗流过程。结果表明,随着孔隙平均Kn数的增加,多孔介质内的高渗区域增加,且优先从小孔隙中开始增加,这是由于小孔隙中微尺度效应更加明显,相对大孔隙流动阻力更小所致。

In this paper,a multi-relaxation-time lattice Boltzmann model for simulating gas flow in complex microchannels is constructed.The dynamic slip boundary over a curved surface is adopted,and the micro-scale effect and the influence of the Knudsen layer are considered.To describe slip velocity in the microchannel accurately,the local Knudsen number in the pores is introduced instead of the average Knudsen number.Then the Poiseuille flow is simulated to validate the proposed model.The simulation results are in good agreement with the results obtained by the direct Monte Carlo method and molecular simulation,which proves the feasibility of the proposed model in simulating gas flow in microchannels in the slip zone and transition zone.Finally,the gas seepage process in porous media is investigated.The results show that as the average Knudsen number of pores increases,the high permeability area in the porous media increases,and it increase more at smaller cross-sections,because the micro-scale effect is more obvious in the small pores,which is caused by the smaller flow resistance in the relatively small pores.