Dynamics of Gas Molecule near the Surface in Rarefied Flow

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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.