title: Motion of micrometer sized spherical particles exposed to a transient radial flow: attraction, repulsion, and rotation.
abstract: It is now accepted that the physical forces in ultrasonic cleaning are due to strongly pulsating bubbles driven by the sound field. Here we have a detailed look at bubble induced cleaning flow by analyzing the transport of an individual particle near an expanding and collapsing bubble. The induced particulate transport is compared with a force balance model. We find two important properties of the flow which explain why bubbles are effectively cleaning: During bubble expansion a strong shear layer loosens the particle from the surface through particle spinning and secondly an unsteady boundary layer generates an attractive force, thus collecting the contamination in the bubble's close proximity.
authors: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
authors: S Roberto
authors: SR
authors: Gonzalez-Avila
authors: Xiaohu
authors: X
authors: Huang
authors: Pedro A
authors: PA
authors: Quinto-Su
authors: Tom
authors: T
authors: Wu
authors: Claus-Dieter
authors: CD
authors: Ohl