大密度变化非连续介质气体流场的数值仿真

针对大密度变化非连续介质气体流场的仿真难题，实现了分区可变时间步长方法，为了保证宏观物理量通量在界面上连续，针对穿过两个时间步长不相等的区之间的界面的分子执行剩余时间缩放处理。提出了一种高效的分区界面和壁面处理算法，将每个界面设定为只属于一个区，将跨过多个区的壁面分解成分别只属于一个区的多个壁面，并规定仿真分子只能与本区的界面和壁面相互作用。对喷管流场的模拟表明，此方法可以大大提高计算效率。

Numerical Simulation of Non-continuum Gas Flows with Large Density Variation

To solve the problem of the simulation of gas flows with large density variation, the multi-region variable time step method was implemented. A remaining time scaling process should be performed for the molecules passing through the interface between two regions with different time steps, thus the continuity of the macroscopic flux across the interface could be maintained. An efficient multi-region interface and surface processing algorithm was presented. It prescribed that each interface belonged to only one region, and the wall surface spanning multi-region was split into a plurality of wall surfaces, each of them belonged to only one region. A simulation molecule could only interact with the interface and wall surface of the region the simulation molecule belonged to. The simulation results of a nozzle flow show that this method can significantly improve the computation efficiency.