Multiscale Modeling of Molecular Collision Dynamics

Abstract

The multiscale analysis connects the various thermofluid phenomena at different time and spatial scales. In this research, these scales are classified into three stages: the electronic structure stage, the molecular collision stage, and the rarefied gas flow stage. In this study, these three stages are connected by physically robust models. At the electronic structure stage, an inter/intra‐molecular potential model is constructed using the potential energy surface (PES) derived from ab initio calculations such as the molecular orbital method and the density functional theory. At the molecular collision stage, the semi‐classical/classical trajectory calculation is employed with the PES constructed at the electronic structure stage. Then, the various collision models such as elastic/inelastic/reactive collision cross section and scattering angle are constructed from statistical analysis of the trajectory calculations. Finally, these models are introduced into particle simulation such as the DSMC and the PIC/MC at the rarefied gas flow stage. This multiscale modeling does not require empirical parameters such as the transport coefficients and the assumption of thermal equilibrium. Hence, this method is widely applicable to the various rarefied gas flows including the nonequilibrium flow.