Specific heat ratio effects of compressible Rayleigh-Taylor instability studied by discrete Boltzmann method

TL;DR

This study uses the discrete Boltzmann method to analyze how the specific heat ratio influences the thermodynamic non-equilibrium effects and evolution of compressible Rayleigh-Taylor instability, revealing key physical mechanisms.

Contribution

It introduces a non-equilibrium statistical physics approach to study the impact of specific heat ratio on compressible RT instability, which is less explored in traditional macroscopic analyses.

Findings

TNE intensity first increases then decreases with system evolution.

Lower specific heat ratio enhances TNE effects.

The temperature gradient deviation indicates vortex formation.

Abstract

Rayleigh-Taylor (RT) instability widely exists in nature and engineering fields. How to better understand the physical mechanism of RT instability is of great theoretical significance and practical value. At present, abundant results of RT instability have been obtained by traditional macroscopic methods. However, research on the thermodynamic non-equilibrium (TNE) effects in the process of system evolution is relatively scarce. In this paper, the discrete Boltzmann method based on non-equilibrium statistical physics is utilized to study the effects of the specific heat ratio on compressible RT instability. The evolution process of the compressible RT system with different specific heat ratios can be analyzed by the temperature gradient and the proportion of the non-equilibrium region. Firstly, as a result of the competition between the macroscopic magnitude gradient and the non-equilibrium region, the average TNE intensity first increases and then reduces, and it increases with the specific heat ratio decreasing; the specific heat ratio has the same effect on the global strength of the viscous stress tensor. Secondly, the moment when the total temperature gradient in y direction deviates from the fixed value can be regarded as a physical criterion for judging the formation of the vortex structure. Thirdly, under the competition between the temperature gradients and the contact area of the two fluids, the average intensity of the non-equilibrium quantity related to the heat flux shows diversity, and the influence of the specific heat ratio is also quite remarkable.