Reactive Rayleigh-Taylor systems: flame propagation and non-stationarity

TL;DR

This paper investigates reactive Rayleigh-Taylor systems through high-resolution 2D simulations, examining how turbulence and reaction rates influence flame propagation and system non-stationarity, revealing effects like enhanced mixing and intermittency.

Contribution

It introduces a self-consistent lattice Boltzmann simulation approach to study the interplay between turbulence and reaction in Rayleigh-Taylor systems across different reaction rates.

Findings

Turbulent mixing enhances flame propagation in slow-reaction regimes.

Fast reactions slow turbulence growth and create sharp, wrinkled fronts.

Fast reactions increase small-scale temperature intermittency.

Abstract

Reactive Rayleigh-Taylor systems are characterized by the competition between the growth of the instability and the rate of reaction between cold (heavy) and hot (light) phases. We present results from state-of-the-art numerical simulations performed at high resolution in 2d by means of a self-consistent lattice Boltzmann method which evolves the coupled momentum and thermal equations and includes a reactive term. We tune the parameters affecting flame properties, in order to address the competition between turbulent mixing and reaction, ranging from slow to fast-reaction rates. We also study the mutual feedback between turbulence evolution driven by the Rayleigh-Taylor instability and front propagation against gravitational acceleration. We quantify both the enhancement of flame propagation due to turbulent mixing for the case of slow reaction-rate as well as the slowing down of turbulence growth for the fast reaction case, when the flame quickly burns the gravitationally unstable phase. An increase of intermittency at small scales for temperature characterizes the case of fast reaction, associated to the formation of sharp wrinkled fronts separating pure hot/cold fluids regions.