Redistribution of the post-reaction internal energies in DSMC using quantum-kinetic model

Abstract

The Direct Simulation Monte Carlo (DSMC) method has been largely adopted to analyze problems regarding hypersonic, non-equilibrium, and microscopic flows. In this study, we investigate the thermal-chemical effects on combustion at the microscopic scale using this particle collision-based method. It is realized that the existing Larsen-Borgnakke (L-B) model dealing with transfers of various internal energies cannot provide valid solutions for the reactions, and consequently the system fails to reach thermal equilibrium. To overcome this problem, we propose a modified quantum-kinetic (Q-K) model and corresponding redistribution algorithm to satisfy the required detailed balance, based on the solver dsmcFoam+ in the open-source software OpenFOAM. This allows a more straightforward way to handle post-energy redistribution in chemical reactions in comparison to those of the other methods, thus reducing the computational cost and manipulation. To verify the accuracy, spontaneous combustion of premixed $H_2/O_2$ is simulated, which includes polyatomic reactions and non-equilibrium processes, followed by three-dimensional simulation for the Mars Pathfinder probe. Compared with the L-B redistribution method, substantial improvement and excellent solutions to the issues are demonstrated by using the new approach, paving the way for accurate and efficient studies of complex problems involving polyatomic chemical reactions and non-equilibrium processes.