The mechanism of generation of acoustic streaming

Acoustic streaming is a stationary fluid motion induced by intense ultrasound. This paper describes the mechanism of generation of acoustic streaming, theoretically and experimentally. A qualitative explanation in relation to acoustic radiation pressure is followed by a detailed discussion based on the formulation of the phenomenon. The spatial non-uniformity of the sound field and energy dissipation due to viscosity are requisite for the generation of streaming. In the development of streaming, two kinds of nonlinearity are important: one is fluid-dynamic nonlinearity, which accounts for effects of inertial force compared to viscous force in fluid motion, and the other is acoustic nonlinearity, which determines the driving force of streaming. © 1998 Scripta Technica, Electron Comm Jpn Pt 3, 81(10): 1–8, 1998