Rovibrational-Specific QCT Database and Master Equation Study on Hydrogen System in High-Energy Collisions

This work performed quasi-classical trajectory (QCT) calculations for the H2 (X1Σg+)+H(2S) system using the most recent ab initio BH PES and constructed the full state-to-state (StS) kinetic database. From the detailed analysis using the full StS model, it was confirmed that the H2 (X1Σg+) + H(2S) system shows a unique relaxation behavior in which the vibrational relaxation occurs faster than the rotational relaxation during the early stage of the collision. Based on the dynamical characteristics identified from the full StS model, two reduced-order models for CFD applications were proposed. In the modified two-temperature model, the vibrational relaxation time, the dissociation rate coefficients in the quasi-steady-state region, and the vibrational energy loss ratio due to dissociation were provided. A new hybrid binning model applicable to coarse-graining QCT was also proposed. In this method, the graph-based grouping and the centrifugal-barrier-based grouping were applied to the states that strongly influence energy transfer and dissociation, respectively. Compared with the conventional vibration-specific and energy-based models in the 0-D reactor and 1-D post-shock analyses, the hybrid binning model showed better agreement with the full StS results in both the energy transfer and dissociation processes.