Theory of Nonlinear Acoustic Forces Acting on Inhomogeneous Fluids

TL;DR

This paper develops a first-principles nonlinear acoustic theory for inhomogeneous fluids, explaining streaming suppression and fluid relocation phenomena observed in microchannels without relying on mean Eulerian pressure assumptions.

Contribution

It introduces a novel nonlinear acoustic framework for inhomogeneous fluids that accurately predicts fluid behavior in microfluidic environments, challenging previous hypotheses.

Findings

Predicts fluid relocation to pressure nodes in standing waves

Explains streaming suppression in inhomogeneous fluids

Aligns with recent experimental observations

Abstract

Recently, the phenomena of streaming suppression and relocation of inhomogeneous miscible fluids under acoustic fields were explained using the hypothesis on mean Eulerian pressure. In this letter, we show that this hypothesis is unsound and any assumption on mean Eulerian pressure is needless. We present a theory of non-linear acoustics for inhomogeneous fluids from the first principles, which explains streaming suppression and acoustic relocation in both miscible and immiscible inhomogeneous fluids inside a microchannel. This theory predicts the relocation of higher impedance fluids to pressure nodes of the standing wave, which agrees with the recent experiments.