Direct Simulation Monte Carlo Method on Gas Flow with Vortexes

Two-dimensional gas flow between two concentric cylinders is calculated by the direct simulation Monte Carlo method (DSMC) using sebcell method and the maximum collision number method. The maximum collision number method that is incorporated with the subcell method can reduce the lower limit of the average number of molecules in a cell to one less, and it does not necessarily require a calculating time longer than a conventional collision method. The DSMC method can analyze continuum flow with different point of view from the continuum mathematical approach. The flow of gas becomes unstable as density increases, and obstacles inserted into the flow promote formation of vortexes. Since the time step used in the DSMC is an order of the mean collision time of molecules, the formation and deformation of vortexes are investigated with high resolution of time