Analysis of flow characteristics through micro and nano channels with adsorbates.

从理论上研究了其他气体分子在微纳通道壁面物理吸附时反射气体分子的特性。根据不同的表面特性，计算了气体分子对壁面的容纳量以及壁面上的应力和能量通量。我们把铂表面作为固体壁，氮气和氩气分子作为气体分子。考虑了库埃特流动和两个温度不同的平行壁面之间的热问题。本分析中考虑的壁温为300K。我们用DSMC方法研究气体分子在两壁间的运动，用分子动力学方法研究气体分子与壁面的相互作用。考虑了两种壁面结构，即分子尺度的光滑表面和沟槽表面。还考虑了吸附气体分子的壁面。研究结果表明：不同槽向的调节系数不同；吸附壁面的这些值远高于清洁壁面的这些值。计算值与实验值吻合较好。提出了壁面反射分子速度分布函数的一个新的边界条件。即在每个速度方向上的分布是分开的，具有麦克斯韦型分布，本文计算了容纳系数。结果表明，所提出的边界条件较好地描述了流体的流动特性。利用所提出的边界条件，分析了混合气体的微通道流动，阐明了吸附物对通道通量的影响

The characteristics of the reflected gas molecules were theoretically investigated when other gas molecules are physically adsorbed on the wall surface of micro and nano channels. The accommodation of gas molecules to the wall, and the stress and energy flux on the wall are calculated for various surface characters. We took the platinum surface as a solid wall, and nitrogen and argon molecules as gas molecules. The Couette flow and the thermal problem between two parallel walls whose temperatures are different each other are considered. The wall temperature considered in the present analysis is 300K. We apply the DSMC method for the motion of gas molecules between two walls and the molecular dynamics methods for the interaction between gas molecule and the wall surface. Two cases of wall surface structure are considered, that is, a smooth surface and a grooved surface of molecular scale. The wall surfaces with adsorbed gas molecules are also considered.We obtained the following results : the accommodation coefficients are different for different groove direction. These values on the adsorbed wall surface are much higher than those on the clean surface. The values calculated are in good agreement with the experimental values. We proposed a new boundary condition of the velocity distribution function for the reflected molecules at the wall surface. Namely, the distributions are separated in each velocity direction, and it has the Maxwell-type distribution with accommodation coefficient calculated in the present study. It was found that the proposed boundary condition well describes the flow behavior.Using the boundary conditions proposed, we analyzed the micro-channel flow of gas mixtures, and clarified the effect of the adsorbates on the flux through the channel