An ES-BGK model for diatomic gases with correct relaxation rates for internal energies

TL;DR

This paper introduces a new ES-BGK model for diatomic gases that accurately captures energy exchanges between translational, rotational, and vibrational modes, aligning with physical relaxation rates and satisfying the H-theorem.

Contribution

The paper develops a novel ES-BGK model that incorporates realistic energy exchange mechanisms and collision numbers for diatomic gases, ensuring physical consistency and correct transport properties.

Findings

Model satisfies the H-theorem.

Accurately reproduces transport coefficients.

Aligns with Landau-Teller and Jeans relaxation equations.

Abstract

We propose a new ES-BGK model for diatomic gases which allows for translational-rotational and translational-vibrational energy exchanges, as given by Landau-Teller and Jeans relaxation equations. This model is consistent with the general definition of the vibrational and rotational collision numbers that are also commonly used in DSMC solvers. It is proved to satisfy the H-theorem and to give the correct transport coefficients, up to the volume viscosity.