Improved null-collision technique in the direct simulation Monte Carlo method: Application to vibrational relaxation of nitrogen

The improved null-collision (INC) technique in the direct simulation Monte Carlo (DSMC) method is developed for the simulation of diatom-diatom collision processes and detailed for elastic and rotationally and vibrationally inelastic collision processes in a spatially homogeneous cell using the realistic cross-sections. The accuracy of the INC-DSMC method is assessed by comparing with the solution of the master relaxation equation for the vibrational relaxation of nitrogen in an isolated spatially homogeneous cell. The feasibility of the INC-DSMC method for practical use is verified by simulating a hypersonic rarefied nitrogen flow over a circular cylinder.