Nonequilibrium Coupled Vibration–Dissociation Model for Direct Simulation Monte Carlo

Accurate modeling of vibration–dissociation coupling remains a primary challenge in the direct simulation Monte Carlo framework for hypersonic reacting flows because conventional phenomenological models often rely on equilibrium assumptions or empirical calibration. To address this, a novel nonequilibrium coupled vibration–dissociation (NCVD) model is proposed. Built within a physically constrained deconvolution framework based on a two-temperature energy distribution, the NCVD model explicitly incorporates two critical nonequilibrium indicators (the nonequilibrium rate factor and the average vibrational energy of dissociating molecules) into the microscopic collision probability. Unlike traditional models, the present formulation ensures a consistent mapping between macroscopic nonequilibrium behaviors and microscopic kinetics. Comprehensive zero-dimensional heat-bath simulations demonstrate that the NCVD model quantitatively reproduces the target dissociation characteristics in both vibrationally cold and hot conditions, significantly outperforming the standard total collision energy (TCE) and vibrationally favored dissociation models. Furthermore, in one-dimensional simulations of high-enthalpy shock-heated oxygen flows, the NCVD model shows superior agreement with experimental measurements and state-to-state calculations for vibrational temperature and species concentration profiles. The proposed NCVD model for simulating thermochemical nonequilibrium flows proves to offer a robust compromise between physical fidelity and computational cost, maintaining efficiency comparable to the TCE model for engineering applications.