Bubble collapse near porous plates

TL;DR

This study investigates how porous boundaries influence bubble collapse dynamics, focusing on displacement and rebound size, and extends a numerical model to predict these effects based on porosity and standoff distance.

Contribution

It provides the first experimental analysis of bubble collapse near porous surfaces and extends a numerical model to account for porosity effects.

Findings

Bubble displacement depends mainly on standoff distance and porosity.

Bubble rebound size is primarily influenced by porosity.

Experimental data align with the extended numerical model.

Abstract

The collapse of a gas or vapour bubble near a non-porous boundary is directed at the boundary due to the asymmetry induced by the nearby boundary. High surface pressure and shear stress from this collapse can damage, or clean, the surface. A porous boundary, such as a filter, would act similarly to a non-porous boundary but with reduced asymmetry and thus reduced effect. Prior research has measured the cleaning effect of bubbles on filters using ultrasonic cleaning, but it is not known how the bubble dynamics are fundamentally affected by the porosity of the surface. We address this question experimentally by investigating how the standoff distance, porosity, pore size, and pore shape affect two collapse properties: bubble displacement and bubble rebound size. We show that these properties depend primarily on the standoff distance and porosity of the boundary and extend a previously developed numerical model that approximates this behaviour. Using the numerical model in combination with experimental data, we show that bubble displacement and bubble rebound size each collapse onto respective single curves.