Mixing effectiveness depends on the source-sink structure: Simulation results

TL;DR

This paper demonstrates through particle-based simulations that the effectiveness of mixing in fluid flows significantly depends on the spatial arrangement of sources and sinks, with results showing how this relationship varies with the Peclet number.

Contribution

The study provides quantitative simulation evidence that mixing enhancement is influenced by source-sink structure, extending understanding of flow mixing efficiency.

Findings

Mixing enhancement varies with source-sink configuration.

Dependence of mixing efficiency on Peclet number confirmed.

Simulation results support theoretical predictions.

Abstract

The mixing effectiveness, i.e., the enhancement of molecular diffusion, of a flow can be quantified in terms of the suppression of concentration variance of a passive scalar sustained by steady sources and sinks. The mixing enhancement defined this way is the ratio of the RMS fluctuations of the scalar mixed by molecular diffusion alone to the (statistically steady-state) RMS fluctuations of the scalar density in the presence of stirring. This measure of the effectiveness of the stirring is naturally related to the enhancement factor of the equivalent eddy diffusivity over molecular diffusion, and depends on the Peclet number. It was recently noted that the maximum possible mixing enhancement at a given Peclet number depends as well on the structure of the sources and sinks. That is, the mixing efficiency, the effective diffusivity, or the eddy diffusion of a flow generally depends on the sources and sinks of whatever is being stirred. Here we present the results of particle-based simulations quantitatively confirming the source-sink dependence of the mixing enhancement as a function of Peclet number for a model flow.