Front speed in reactive compressible stirred media

TL;DR

This study examines how compressibility influences front propagation and burning rates in reactive flows, revealing modest increases in bulk burning rate with compressibility, especially in shear flows, and complex behaviors in cellular flows.

Contribution

It provides a quantitative analysis of compressibility effects on front dynamics in reactive flows, comparing shear and cellular flow regimes under fast advection.

Findings

Bulk burning rate increases with compressibility in shear flows.

Reaction speed amplifies differences from laminar cases.

Modest enhancement (<20%) observed in cellular flow scenarios.

Abstract

We investigated a nonlinear advection-diffusion-reaction equation for a passive scalar field. The purpose is to understand how the compressibility can affect the front dynamics and the bulk burning rate. We study two classes of flows: periodic shear flow and cellular flow both in the case of fast advection regime, analysing the system at varying the extent of compressibility and the reaction rate. We find that the bulk burning rate in a shear flow increases with compressibility intensity. Furthermore, the faster the reaction the more important the difference with respect to the laminar case. The effect has been quantitatively measured and it turns out to be generally little. For the cellular flow, the two extreme cases have been investigated, with the whole perturbation situated either in the centre of the vortex or in the periphery. The dependence in this case does not show a monotonic scaling with different behaviour in the two cases. The enhancing remains modest and always less than 20%