Numerical study of three-dimensional single-mode Rayleigh-Taylor instability in turbulent mixing stage

TL;DR

This study uses lattice Boltzmann simulations to analyze the late-stage evolution of 3D single-mode Rayleigh-Taylor instability, revealing stages, complex structures, and growth behaviors influenced by Reynolds and Atwood numbers.

Contribution

It provides detailed numerical insights into the late-time dynamics and phase interface structures of 3D RTI using a mesoscopic lattice Boltzmann approach, highlighting effects of key dimensionless parameters.

Findings

Four development stages identified at high Reynolds number.

Complex interfacial structures observed during turbulent mixing stage.

Spike growth rate increases with Atwood number, bubble growth rate remains constant.

Abstract

Rayleigh-Taylor instability (RTI) as a multi-scale, strongly nonlinear physical phenomenon which plays an important role in the engineering applications and scientific research. In this paper, the mesoscopic lattice Boltzmann method is used to numerically study the late-time evolutional mechanism of three-dimensional (3D) single-mode RTI and the influences of extensive dimensionless Reynolds number and Atwood number on phase interfacial dynamics, spike and bubble growth are investigated in details. For a high Reynolds number, it is reported that the development of 3D single-mode RTI would undergo four different stages: linear growth stage, saturated velocity growth stage, reacceleration stage and turbulent mixing stage. A series of complex interfacial structures with large topological changes can be observed at the turbulent mixing stage, which always preserve the symmetries with respect to the middle axis at a low Atwood number, and the lines of symmetry within spike and bubble are broken as the Atwood number is increased. Five statistical methods for computing the spike and bubble growth rates are then analyzed to reveal the growth law of 3D single-mode RTI in turbulent mixing stage. It is found that the spike late-time growth rate shows an overall increase with the Atwood number, while the bubble growth rate seems to be independence of the Atwood number, approaching a constant of around 0.1. When the Reynolds number decreases, the later stages cannot be reached gradually and the evolution of phase interface presents a laminar flow state.