State-to-state collision integrals and transport coefficients in oxygen mixtures

Abstract

Accurate transport coefficients are critical for predicting aerothermal environments during high-speed flight and atmospheric reentry processes. This study calculates the vibrationally state-resolved transport collision integrals of O2–O and O2–O2 collision systems using the quasi-classical trajectory method based on high-accuracy ab initio potential energy surfaces within the state-to-state kinetic framework. A comprehensive state-resolved collision integral dataset for these systems is provided. The results demonstrate that vibrational excitation strongly influences collision integrals, rotational relaxation times, and transport coefficients, with effects becoming more pronounced at high temperatures. Collision integrals differ by up to 50% between ground and highly excited vibrational states, and state-resolved rotational relaxation times show substantial deviations from traditional Parker model predictions. Transport coefficients calculated for O2/O mixtures of varying composition indicate that, in molecule-dominated mixtures, traditional phenomenological models underestimate shear viscosity and thermal conductivity by 15%–25% above 10 000 K, while significantly overestimating bulk viscosity across the entire temperature range. The present quantitative analysis of vibrational-state effects on collision integrals and transport coefficients delineates the applicability limits of different phenomenological models and provides high-precision data for computational fluid dynamics simulations of high-speed flows.