Simulation Study Of The Transition Zone Flow Dsmc Method

It is a kernel in the ratified gas dynamics to solve the flow problem in the transitional domain. Among the many numerical solving methods, the Direct Simulation Monte Carlo (DSMC) method is the unique one to succeed in solving the problems in the rarified gas dynamics. DSMC method can be proved by experiments from the macroscopic parameters to the microscopic speed distributing functions. The thesis aims to reveal the flow characteristics of the transitional domain and to improve the applying level of the DSMC method. Three kinds of rarified gas flows, which are to be solved immediately, are studied here.The subsonic and supersonic flows in an opening cavity in the transitional domain are simulated by the DSMC method. The forming and developing process of the vortex is exhibited, and the influence of the cavity figure (span-chord ratio), the wall temperature, Knudsen number (rareness) and Mach number is analysed. The result shows that the rareness of gas has great effect on the vortex structure and its position.A series of efficient Bridge-Function-methods suitable to the engineering design are brought forward here. The methods can not only solve the supersonic and hypersonic problems in the transitional flow but also estimate the aerodynamic characteristics of different-figured reentry vehicles in the transitional domain. The same conclusions are drawn through the simulation of the same vehicles by the DSMC method. Thus the efficiency of the Bridge-methods is proved. Moreover, research on the aerodynamic characteristics of a missile of complicated figure is carried out.The similarities and differences between the flow in Micro-Electronic-Mechanic-System(MEMS) and that of the normal devices are found according to lots of reference literatures. The flow model is established and the factors influencing the flow in MEMS are given. What's more, many methods that are applicable to the numerical simulation of the flow problems in the MEMS are presented.