Non-Linear Maximum Entropy Principle for a Polyatomic Gas subject to the Dynamic Pressure

TL;DR

This paper develops a non-linear maximum entropy closure for the extended thermodynamics of polyatomic gases, incorporating dynamic pressure without near-equilibrium assumptions, and demonstrates the model's mathematical well-posedness and agreement with phenomenological theories.

Contribution

It introduces the first non-linear closure for molecular extended thermodynamics of polyatomic gases considering dynamic pressure, without relying on near-equilibrium approximations.

Findings

The distribution function accounts for internal degrees of freedom.

The system is symmetric hyperbolic within bounded dynamic pressure.

Global smooth solutions exist under the model's conditions.

Abstract

We establish Extended Thermodynamics (ET) of rarefied polyatomic gases with six independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting the near-equilibrium approximation. The closure is accomplished by the Maximum Entropy Principle (MEP) adopting a distribution function that takes into account the internal degrees of freedom of a molecule. The distribution function is not necessarily near equilibrium. The result is in perfect agreement with the phenomenological ET theory. To my knowledge, this is the first example of molecular extended thermodynamics with a non-linear closure. The integrability condition of the moments requires that the dynamical pressure should be bounded from below and from above. In this domain the system is symmetric hyperbolic. Finally we verify the K-condition for this model and show the existence of global smooth solutions.