Experimental study of acoustic streaming induced by a sharp edge at different frequencies and vibrating amplitudes

Abstract

Acoustic streaming is the time-averaged flow induced by acoustic waves inside the fluid medium. Much attention has been paid to the streaming flow at the microscale, with the rapid development of microfluidics and significant demand for the microscale manipulation of fluid or particles. Recently, the streaming flow at the audible or lower frequency (10 Hz ? 10 kHz) has been found to be closely associated with local structures, like a sharp edge in the microchannel. By its strong magnitude and low cost, this kind of streaming flow has been applied in various fields. However, the mechanisms behind this non-classical Rayleigh streaming are still not very clear, though its high sensitivity to the thickness of the acoustic boundary layer and unstable streaming pattern under high forcing amplitude have been demonstrated. In this study, experimental work has been conducted, with the help of the Particle Imaginary Velocimetry (PIV) platform, to reveal the influence of frequency and vibrating amplitude on the streaming flow field around a sharp edge with 90?, and its characterized spatial dimension. The scaling law concerning the vibration amplitude and streaming velocity has been come up with, and the parameter frequency is also included. The expression f -1/6va2~vsy,max demonstrates a good prediction in terms of the streaming magnitude, in comparison with experimental results.