Multiscale Analysis of Nonequilibrium Rarefied Gas Flows (Keynote)

The practical method for solving the nonequilibrium rarefied gas flows is introduced in this paper. This method based on the multi-scale analysis connects the thermofluid phenomena that occur in the different time scale and spatial scale by constructing the reasonable physical model among them. As a example of the analysis, the molecular collision of silane gas, which is widely used in the semiconductor manufacturing process, is considered here. First, the new site-to-site intermolecular potential model is determined from the accurate ab initio molecular orbital (MO) calculations. Next, the collision models such as the collision cross section and the scattering angle are constructed by the statistical analysis of classical trajectory (CT) calculations using the new potential model. Finally, these collision models are applied into the direct simulation Monte Carlo (DSMC) calculation. In this way, this multi-scale model does not require the empirical parameters such as the transport coefficients and widely applicable to the various rarefied gas flows including the nonequilibrium of flow filed.