Effects of Molecular Diffusivity on Shock Wave Structures in Monatomic Gases

TL;DR

This paper investigates how molecular diffusivity affects shock wave structures in monatomic gases, demonstrating improved hydrodynamic models that better match experimental and theoretical data across a wide Mach number range.

Contribution

It introduces constitutive equations derived from a Burnett regime model that enhance shock structure predictions in monatomic gases.

Findings

Improved agreement with experimental shock profiles.

Enhanced temperature and density profile predictions.

More accurate than classical and expansion-based models.

Abstract

We present a full investigation into shock wave profile description using hydrodynamics models. We identified constitutive equations that provide better agreement for all parameters involved in testing hydrodynamic equations for the prediction of shock structure in a monatomic gas in the Mach number range $1.0-11.0$. The constitutive equations are extracted from a previously derived thermomechanically consistent Burnett regime continuum flow model. The numerical computations of the resulting hydrodynamic equations along with classical ones are performed using a finite difference global solution (FDGS) scheme. Compared to previous studies that focussed mainly on the density profile across the shock, here we also include temperature profiles as well as non-negativity of entropy production throughout the shock. The results obtained show an improvement upon those obtained previously in the bi-velocity (or volume/mass diffusion) hydrodynamics and are more accurate than in the hydrodynamic models from expansions method solutions to the Boltzmann equation.