Oscillating reaction in porous media under saddle flow

TL;DR

This study investigates pattern formation in oscillating chemical reactions within porous media under saddle flow, revealing how flow heterogeneity and Péclet number influence pattern characteristics and stability.

Contribution

It introduces analysis of oscillating reactions in porous media with saddle flow, highlighting the role of flow heterogeneity and dispersion in pattern formation, which was not addressed in prior simple flow studies.

Findings

Patterns are controlled by flow stagnation points and manifolds.

Pattern features depend on Péclet number (Pe).

Heterogeneous flow fields influence pattern stability.

Abstract

Pattern formation due to oscillating reactions represents variable natural and engineering systems, but previous studies employed only simple flow conditions such as uniform flow and Poiseuille flow. We studied the oscillating reaction in porous media, where dispersion enhanced the spreading of diffusing components by merging and splitting flow channels. We considered the saddle flow, where the stretching rate is constant everywhere. We generated patterns with the Brusselator system and classified them by instability conditions and P\'eclet number (Pe), which was defined by the stretching rate. The results showed that each pattern formation was controlled by the stagnation point and stable and unstable manifolds of the flow field due to the heterogeneous flow fields and the resulting heterogeneous dispersion fields. The characteristics of the patterns, such as the position of stationary waves parallel to the unstable manifold and the size of local stationary patterns around the stagnation point, were also controlled by Pe.