Frozen Fronts Selection in flow against self-sustained chemical waves

TL;DR

This study investigates the formation and characteristics of stationary frozen fronts in autocatalytic chemical waves under forced flow, combining experiments, analysis, and simulations to understand their shapes and conditions.

Contribution

It provides a comprehensive analysis of frozen front formation in autocatalytic reactions with flow, highlighting the types, conditions, and theoretical descriptions of these fronts.

Findings

Identification of upstream and downstream frozen fronts around a solid disk

Range of flow velocities supporting frozen fronts delineated

Validation of eikonal approximation for front shape prediction

Abstract

Autocatalytic reaction fronts between two reacting species in the absence of fluid flow, propagate as solitary waves. The coupling between autocatalytic reaction front and forced hydrodynamic flow may lead to stationary front whose velocity and shape depend on the underlying flow field. We focus on the issue of the chemo-hydrodynamic coupling between forced advection opposed to self-sustained chemical waves which can lead to static stationary fronts, i.e Frozen Fronts, $FF$. Towards that purpose, we perform experiments, analytical computations and numerical simulations with the autocatalytic Iodate Arsenious Acid reaction ($IAA$) over a wide range of flow velocities around a solid disk. For the same set of control parameters, we observe two types of frozen fronts: an upstream $FF$ which avoid the solid disk and a downstream $FF$ with two symmetric branches emerging from the solid disk surface. We delineate the range over which we do observe these Frozen Fronts. We also address the relevance of the so-called eikonal, thin front limit to describe the observed fronts and select the frozen front shapes.