Tensor Temperature and Shockwave Stability in a Strong Two-Dimensional Shockwave

TL;DR

This study investigates temperature anisotropy and stability in strong two-dimensional shockwaves using molecular dynamics, finding that certain temperature definitions work better and that these shockwaves are stable against perturbations.

Contribution

It introduces a local particle-based temperature definition that avoids self-contribution issues and demonstrates the stability of 2D shockwaves against sinusoidal perturbations.

Findings

Local particle-based temperature is most effective.

Configurational temperature can be negative and unstable.

2D shockwaves are stable to sinusoidal perturbations.

Abstract

The anisotropy of temperature is studied here in a strong two-dimensional shockwave, simulated with conventional molecular dynamics. Several forms of the kinetic temperature are considered, corresponding to different choices for the local instantaneous stream velocity. A local particle-based definition omitting any "self" contribution to the stream velocity gives the best results. The configurational temperature is not useful for this shockwave problem. Configurational temperature is subject to a shear instability and can give local negative temperatures in the vicinity of the shock front. The decay of sinusoidal shockfront perturbations shows that strong two-dimensional planar shockwaves are stable to such perturbations.