Mechanism-specific chemical energy accommodation with finite-rate surface chemistry in non-equilibrium flow.

This article focuses on modeling mechanism-specific chemical energy accommodation (CEA) during heterogeneous recombination on vehicle surfaces in rarefied hypersonic flows encountered during atmospheric reentry. Using the finite-rate surface chemistry (FRSC) model integrated within the Direct Simulation Monte Carlo (DSMC) framework, the study distinguishes between the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) recombination mechanisms, assigning distinct CEA coefficients (β) to each. Verification against analytical Langmuir isotherm solutions and validation with benchmark cases demonstrate that incorporating mechanism-specific CEA reduces predicted total surface heat flux (q_tot) by up to 14.44% compared to the complete CEA assumption. Parametric analyses reveal that the ER mechanism's contribution—and thus the impact of mechanism-specific CEA—increases with higher atomic partial pressures near the surface, suggesting that accounting for mechanism-specific CEA is important for accurate heat flux predictions on reentry vehicle surfaces under varying flow conditions.