Modified Collision Energy, a New Chemical Model in the DSMC Algorithm

Abstract

A new chemical model in the direct simulation Monte Carlo (DSMC) algorithm, entitled modified collision energy (MCE), has been developed for simulation of reactive rarefied flows without some limitations of the conventional macroscopic models. Determination of correct values of the experimental parameters for computing the Arrhenius reaction rate is a serious challenge in some macroscopic chemical reaction models such as total collision energy (TCE) and general collision energy (GCE). A slight variation of these constant parameters in the Arrhenius relation could lead to significant change in the results. On the other hand, these experimental parameters have been extracted empirically only for limit number of gases and so they cannot be used for simulation of chemical reactions in various types of gases. Since some of these constants have been determined experimentally by several studies, they have been reported by different values in different references. The proposed MCE model in the present study is a reliable method to properly determine values of these parameters for all types of gases with the intrinsic properties of the particles and without need of any experimental data. Extraction of the constant parameters has been carried out using the analytical method or numerical quantum kinetics (QK) or modified quantum kinetics (MQK) models. The proposed MCE method has been evaluated in four test cases, including assessment of the reaction rate in equilibrium and nonequilibrium conditions, studying of the rarefied flow along the stagnation line, and investigation of the hypersonic gas flow over the axial symmetry blunt nose. The results show that the proposed method has desirable accuracy without use of any experimental parameters. The MCE method can also be used to calibrate the macroscopic reactive models such as the TCE and GCE.