Ultrarelativistic limit of a Rarefied Gas with Internal Structure

Non-equilibrium theories of rarefied gases: internal variables and extended thermodynamics

Limits of classical constitutive laws such as Fourier and Navier-Stokes equations are discovered since decades. However, the proper extensions -- generalizations of these are not unique. They differ in the underlying physical principles and in modeling capabilities. In this paper, two different theories are discussed and compared to each other, namely the kinetic theory-based Rational Extended Thermodynamics (RET) and non-equilibrium thermodynamics with internal variables (NET-IV). First, the paper starts with the case of rigid heat conductors summarizing the result achieved so far. Then a typ…

On the rarefied gas experiments

There are limits of validity of classical constitutive laws such as Fourier and Navier-Stokes equations, phenomena beyond those limits have been experimentally found many decades ago. However, it is still not clear what theory would be appropriate to model different non-classical phenomena under different conditions considering either the low-temperature or composite material structure. In this paper, a modeling problem of rarefied gases is addressed. It covers the mass density dependence of material parameters, the scaling properties of different theories and aspects of how to model an experi…

一种适用于内部态密度与温度无关的非多方气体的新型 ES-BGK 模型

A Novel ES-BGK Model for Non-Polytropic Gases with Internal State Density Independent of the Temperature

提出一种内部态密度仅依赖微观能量、满足 H 定理且可由最大熵原理封闭矩方程的新型 ES-BGK 非多方稀薄气体模型，CO₂ 平面激波模拟显示内部温度呈单调剖面。

Which moments are appropriate to describe gases with internal structure in Rational Extended Thermodynamics?

Motivated by a recent paper of Pennisi (2021) in the relativistic framework, we revisit the previous approach of two hierarchies of moments critically and propose a new natural physical hierarchy of moments to describe classical rarefied non-polytropic polyatomic gas in the framework of Molecular Rational Extended Thermodynamics. The differential system of the previous approach is proved to be a \emph{principal subsystem} of the present one. The main idea is that at the molecular level, the total energy is the kinetic energy plus the energy of internal mode due to the rotation and vibration, a…