微通道内气体流动的DSMC方法

基于压力边界条件开展了微尺度低速流动DSMC方法的研究, 定义了两个无量纲参数作为微尺度DSMC方法下网格尺寸与时间步长的约束条件, 通过微尺度Poiseuille流进行了方法的验证与比较, 获得了网格尺寸与时间步长的一般原则。在此基础上, 对变截面的单孔和双孔模型的微通道气体流动进行DSMC模拟, 结果表明, 通道几何形状对微尺度气体流动具有显著影响, 孔口后由于通道收缩, 产生压降, 导致气流加速, 并在孔口下游拐角处发生分离; 双孔口模型的流动结构与单孔口模型相似, 且在相同压差情况下, 经双孔口后的气体流速低于经单孔口后的气体流速; 随着入口压力的增加, 经过孔口压缩后的速度越大, 分离区尺寸也越大。 

Gas Flow in Microchannel by DSMC Method

Based on the pressure boundary conditions, the DSMC method for micro scale flow was studied. Two dimensionless parameters were defined as the constraints of grid size and time step for the micro scale DSMC method. The method was verified and compared through the micro scale Poiseuille flow, and the general principle of selecting grid size and time step was preliminarily obtained. On this basis, the DSMC simulation of microchannel gas flow with variable flow cross section was carried out. The flow structures of single orifice and double orifice models and the influence of inlet pressure conditions on the internal flow were mainly studied. The results show that the channel geometry has a significant effect on the micro gas flow. The channel shrinks behind the orifice, resulting in a pressure drop, which further leads to the acceleration of gas flow and the flow separation at downstream corners of the orifice. The flow structure of the double orifice model is similar to that of the single orifice model, and the gas velocity through the double orifice is lower than that through the single orifice under the same pressure difference. With the increase of inlet pressure, the flow velocity after compression becomes larger and the size of separation zone also becomes larger.