Multi-Monte Carlo Methods for Inter-particle Collision
考虑颗粒碰撞的多重Monte Carlo算法

In the interest of improving collision arithmetic and decreasing computation cost, a new Multi-Monte Carlo (MMC) method for inter-particle collision is promoted. The particle motion is described by the Langevin equations, which are solved by Monte Carlo (MC) method. On the same time, inter-particle collision is modeled by Direct Simulation Monte Carlo (DSMC) method, which is coupled with the forenamed MC method. The simulation particles of MMC method are fictitious particles, the number of which is far less than that of real particles. In order to found an integrated MMC method for inter-particle collision, a series of methods are developed, which include the setting of time step, the judgment of control volume in which fictitious collision partner lies, the judgment of the occurrence of inter-particle collision event, the choice of fictitious collision partner, and particle collision dynamics based on stochastic collision angle. Fine particles flows and heavy coarse particles flows are chosen as standard cases to validate MMC method. The simulation results of MMC method are in good agreement with that of both analytical solution and Direct Numerical Simulation (DNS), not only on macroscopical facets such as particle collision frequency, but also on microcosmic facets such as time-averaged or special-time-point particle number density, particle velocity and particle turbulent kinetic energy etc. The results of numerical simulation show that MMC method for inter-particle collision has not only enough low computation cost but also enough high computation precision.