DSMC analysis of bipropellant thruster plume impingement by a grouping species method

Abstract

A grouping species method is proposed to reduce computing time in the DSMC computations. The method is based on Dalton's law of partial pressures for a mixture of gases. A mixture of gases is classified into fewer new artificial species. Each new artificial species represents a group of species to which it belongs. The criterion of grouping species is molecular mass similarity. Because molecule masses contribute mainly in a binary elastic collision. As fewer artificial species by the grouping species method are used in the exhaust plume of bipropellant thruster DSMC computation, it can further save computation time due to fewer amounts of iterations of the simulated molecule movement, interactions with boundaries, intermolecular collisions, sampling of the flow properties, and writing the output files in comparison with the nominal computation. The results of the 10 species nominal case and those of 5 artificial species case are compared respectively and similar results being found with reasonable accuracy, while reducing computing time by 50 %. Therefore, the proposed grouping species method can enhance the DSMC analysis efficiency of parametric studies with many design parameters, e.g. thruster tilt angle, position, and the distance between thruster position and the sensitive surfaces.