Stagnation points control chaotic fluctuations in viscoelastic porous media flow

TL;DR

This paper investigates how stagnation points influence chaotic flow in viscoelastic porous media, revealing that geometric disorder can either suppress or promote chaos depending on initial conditions, challenging previous assumptions.

Contribution

It demonstrates experimentally that geometric disorder alone does not suppress chaos; instead, stagnation points affected by initial conditions play a key role.

Findings

Disorder can promote chaotic fluctuations with modified initial conditions.

Stagnation points are crucial in controlling flow stability.

Geometric disorder's effect depends on initial flow configuration.

Abstract

Viscoelastic flows through porous media become unstable and chaotic beyond critical flow conditions, impacting industrial and biological processes. Recently, Walkama \textit{et al.} [Phys. Rev. Lett. \textbf{124}, 164501 (2020)] have shown that geometric disorder greatly suppresses such chaotic dynamics. We demonstrate experimentally that geometric disorder \textit{per se} is not the reason for this suppression, and that disorder can also promote choatic fluctuations, given a slightly modified initial condition. The results are explained by the effect of disorder on the occurrence of stagnation points exposed to the flow field, which depends on the initially ordered geometric configuration.