Influence of chemical models on the computation of thermo-fluid-dynamic parameters in hypersonic, rarefied flows

Four different chemical models (Bird, Fan and Shen, ‘classic’, and ‘new’ quantic) have been implemented in a direct simulation Monte Carlo (DSMC) code for comparison purpose. Computer tests simulated a hypersonic, rarefied flow field past a bluff (or flat-ended) cylinder; the working gas was nitrogen. The flow field parameters were compared with those from the advanced DS2V code. The Stanton number at the stagnation point was compared also with the experimental data. The present analysis showed that the Fan–Shen model is comparable with the widely accepted Bird model. The results from the DSMC code based on these models are close to those computed by DS2V and to the experimental data. The good comparison of the Bird and the Fan–Shen models is a very important result both from a physical point of view, because the two models rely on different approaches, and from an operative point of view, because the Fan–Shen model could be considered as a possible alternative to the Bird model. On the contrary, the quantic models appear to be not suitable.