Discrete Boltzmann modeling of Rayleigh-Taylor instability: effects of interfacial tension, viscosity and heat conductivity

TL;DR

This paper uses the Discrete Boltzmann Method to study how interfacial tension, viscosity, and heat conduction influence the evolution of Rayleigh-Taylor instability in compressible flows, revealing stage-dependent effects on instability growth and entropy production.

Contribution

It introduces a detailed analysis of RTI effects using DBM, highlighting stage-specific influences of interfacial tension, viscosity, and heat conduction, and proposes new criteria for RTI stage transition.

Findings

Interfacial tension inhibits RTI at bubble acceleration stage.

Viscosity and heat conduction suppress RTI evolution.

New criteria for RTI stage transition based on interface length and entropy rates.

Abstract

The Rayleigh-Taylor Instability (RTI) in compressible flow with inter-molecular interactions is probed via the Discrete Boltzmann Method (DBM). The effects of interfacial tension, viscosity and heat conduction are investigated. It is found that the influences of interfacial tension on the perturbation amplitude, bubble velocity, and two kinds of entropy production rates all show differences at different stages of RTI evolution. It inhibits the RTI evolution at the bubble acceleration stage, while at the asymptotic velocity stage, it first promotes and then inhibits the RTI evolution. Viscosity and heat conduction inhibit the RTI evolution. Viscosity shows a suppressive effect on entropy generation rate related to heat flow at the early stage but a first promotive and then suppressive effect on entropy generation rate related to heat flow at a later stage. Heat conduction shows a promotive effect on entropy generation rate related to heat flow at an early stage. Still, it offers a first promotive and then suppressive effect on entropy generation rate related to heat flow at a later stage. By introducing the morphological boundary length, we found that the stage of exponential growth of interface length with time corresponds to the bubble acceleration stage. The first maximum point of interface length change rate and the first maximum point of the change rate of entropy generation rate related to viscous stress can be used as a new criterion for RTI to enter the asymptotic velocity stage.