Acoustofluidic Suppression of Rayleigh Taylor Instability and Fluid Mixing: Stabilization of Stratified Fluids in a Minichannel

TL;DR

This paper introduces an acoustofluidic technique using standing bulk acoustic waves to suppress Rayleigh-Taylor instability and reduce fluid mixing in minichannels, enhancing control over stratified fluids.

Contribution

It demonstrates that acoustic energy density and wave orientation are critical for stabilizing stratified fluids against RTI, providing a new method for fluid control in microfluidic systems.

Findings

Acoustic energy density exceeding a critical threshold suppresses RTI.

Perpendicular wave orientation is essential for effective stabilization.

Mixing index reduced by up to an order of magnitude with acoustic control.

Abstract

Rayleigh-Taylor Instability (RTI) typically arises when a dense fluid is superimposed on a lighter fluid, where the desta- bilizing gravitational force acting on miscible fluids drives chaotic mixing. We theoretically present an acoustofluidic method utilizing standing bulk acoustic waves (BAW) to counteract RTI and suppress the mixing of fluids. To success- fully achieve this suppression, we demonstrate that two concurrent conditions are to be satisfied: the acoustic energy density (Eac) of the standing waves must exceed its critical threshold (Ecr), and the orientation of the acoustic waves must be perpendicular to the fluid-fluid interface. This acoustofluidic mechanism reduces the mixing index (MI) by up to an order of magnitude compared to the mixing induced solely by gravity. By analyzing the interplay between acoustic and gravitational forces, this study provides a comprehensive understanding of acoustically modulated mixing dynamics in minichannels.