Dynamics of Gas Molecule near the Surface in Rarefied Flow

1)利用分子动力学模拟方法，模拟了气体分子在吸附气体分子表面的散射过程。散射过程有四种模式，它们与能量从气体分子转移到其他分子的分布有关。模拟过程中气体分子质量比、势系数、表面吸附质数等参数的变化，研究了它们对散射过程的依赖关系。2)为了研究气体分子在热平衡状态下的黏附和逃逸动力学，对两块铂板间氙分子的行为进行了长时间模拟。转义过程有三种类型。其中两个是由吸附气体分子相互作用引起的。并研究了逃逸分子对覆盖系数的依赖关系。3)采用“直接模拟蒙特卡罗”方法估计了表面粗糙度对稀薄气体流动的影响。测试用例是两个板之间的库埃特流。一个板有一些粗糙度，模拟由车床切割咬伤的形状。高克努森数时，粗糙度的影响通过粗糙度尖锐边缘的某种涡结构到达整个流场。对粗糙度高度、咬合角、克努森数等参数进行了研究。

1) Using the molecular-dynamics simulation method, the scattering process of gas molecule on the surface with adsorbale gas molecules. There are 4 patterns of scattering process, that associated with the distribution of energy-transfer from gas molecule to other molecules. The parameters such as mass ratio of gas molecule, potential coefficients, number of adsorbate on surface are changed in the simulation, and their dependency on the scattering process is studied.2) To study the sticking and escaping dynamics of gas molecule in thermal equilibrium stale, the behavior of Xenon molecules between two plate of Platinum are simulated for a long period. The escaping process has three types. Two of them are caused by interaction from adsorbated gas molecule. Also the dependency of escaping molecules on the coverage coefficients are studied.3) The effrect of roughness of the surface to rarefied gas flow is estimated by "Direct Simulation Monte Carlo" method. The test case is Couette flow between two plates. One plate has some roughness that simulate the shape made by cutting bite of the lathe. With high Knudsen number, the effect of roughness reaches to all the flow field by some vortex structure at the sharp edge of roughness. The parameter study is done on the height of roughness, angle of bite, and Knudsen number.