Mechanisms of removal of micron-sized particles by high-frequencyultrasonic waves

摘要

In this paper, theories of particle removal by high-frequencynultrasonic waves are discussed and tested against recent experimentalndata. First, the principal adhesion forces such as van der Waals forcesnare briefly reviewed and the typical uncertainties in their size innparticle-surface systems are assessed. The different ultrasound-inducednforces-linear forces such as added mass, drag, lift, and Basset forcesnand nonlinear ones due to radiation pressure, and drag exerted bynacoustic streaming-are discussed and their magnitudes are evaluated forntypical cleaning operations. It is shown that high-frequency ultrasoundncan clean particles most effectively in media with properties like waternbecause: (1) the wavelength can be made comparable to the particlenradius to promote effective sound-particle interaction; (2) the viscousnboundary layer is thin, minimizing particle “hide-out;” andn(3) both the added mass and radiation pressure forces exceed typicalnadhesion forces at high frequencies. Based on these analyses, possiblenmechanisms of particle removal are discussed and interpreted in terms ofnexperimental observations of particle cleaning