滑移边界下气膜厚度阶跃变化的阶形板间气体流动

Gas Flow between Plates with Stepped Change of Film Thickness under Sliding Boundary

为进一步研究微尺度下气膜厚度阶跃变化的阶形板间气体流动的相关物理特性,通过代入适用于任意克努森数的新滑移边界条件修正雷诺方程,应用有限体积法迭代求解了阶形板间沿气体流动方向的气膜压力和克努森数分布曲线,沿高度方向的气体流动速度分布曲线,不同环境克努森数下的气膜承载力随速度参数的变化曲线。结果表明:随着气膜间克努森数进入滑流区时,边界速度滑移效应对流体流动特性作用明显,当气膜间克努森数进入过渡区时,一阶滑移与新滑移边界条件间的数值结果产生明显偏差。可知相对于滑移系数固定的一阶滑移边界条件,滑移系数随气膜间克努森数改变而变化的新滑移边界条件,可以更好地描述高度存在阶跃变化即气膜间克努森数跨区域分布的微尺度气体流动。

To understand the physical characteristics of gas flow with stepped change of film thickness between stepped plates on micro scale, the Reynolds equation was modified by introducing a new slip boundary condition suitable for any Knudsen number. The distribution curves of the gas film pressure and the Knudsen number along the gas flow direction, the distribution curve of the gas flow velocity along the height direction, and the variation curve of the gas film bearing capacity with the speed parameters under different environment were solved by using the finite volume method. The results show that the effect of boundary velocity slip on the flow characteristics was obvious when the Knudsen number between gas films entered the slipstream region. When the Knudsen number between gas films entered the transition region, the numerical results of the first-order slip and the new slip boundary conditions deviated considerably. Compared with the first-order slip boundary condition with fixed slip coefficient, the slip coefficient of the new slip boundary condition changed with the change of Knudsen number between gas films, which better described the micro-scale gas flow with the stepped change of gas film thickness and the distribution of Knudsen number across regions.