Single Bubble Cleaning and Vortex Flow

Abstract

Ultrasonic cleaning is a well proven technique in many industrial, laboratory and even household applications. It is known that cavitation bubbles can induce fast microscale flows and thus are responsible for cleaning and even corrosion [1,2]. Nevertheless there are numerous effects that can have a potential role in cleaning processes, as the behavior of an acoustic bubble is very complex: radial oscillations, surface oscillations, leading sometimes to the disintegration of a bubble, collapses, rebounds and subsequently shockwaves, liquid jets and vortex flows can be observed. But as bubbles in sound fields typically appear in a random fashion and in complicated interactions, it is very hard to identify the processes and their effects with respect to cleaning. To isolate the various ongoing processes and to study them in detail, single cavitation bubbles and their interaction with a surface are examined in this work. The single bubbles are of sizes around 500 μm in radius and are produced by a pulsed laser that is focused into water, which allows creating bubbles of a repeatable size at a defined position.