A new approach for chemical reaction simulation of rarefied gas flow by DSMC method

Present study concerns the development of a new approach for chemical reaction modelling in DSMC technique. The conventional quantum-kinetic (QK) method based on the VHS collision model is usually applied by the DSMC algorithm to simulate chemical reactions in rarefied gas flowfield. In this paper, a modified quantum-kinetic model (MQK) is presented to remove some limitation of the QK chemical model. The MQK method uses the GSS collision model based on the Stockmayer potential function which can capture both the attractive and repulsive intermolecular forces and polarization effect of the molecules in the reactive flow. To investigate the accuracy and capability of the proposed model, firstly, dissociation of the nitrogen (non-polar gas) and water vapour (polar gas) are simulated in a single cell DSMC for equilibrium and non-equilibrium conditions. The results of the MQK are assessed with those of the QK methods, analytical models and experimental data. Secondly, dissociation of these two types of gases is studies in the rarefied gas flowfield along the stagnation line of a typical hypersonic atmospheric blunt body problem. The flowfield properties including the density, velocity, transient, vibrational and total temperature along the stagnation line and surface properties including the surface pressure and heatflux at the stagnation point obtained by the MQK model are compared with results of the QK method and available analytical and experimental data. The results show that the MQK model provides more accurate results when the polarization effects and both the attractive-repulsive intermolecular forces are dominant especially at high temperature. Also, comparison of the computational cost between two models indicates higher efficiency using the proposed method rather than the QK model due to reduction of number of the collision pairs.