Cavitation Microstreaming

Abstract

In the research reported here an attempt has been made to discover by experiment what physical assumptions and approximations are appropriate in the theory of cavitation microstreaming, especially for cavitation bubbles located near solid boundaries. A systematic investigation of the phenomenon has been made and its dependence on certain parameters (e.g., amplitude of sound) has been determined. The investigation has disclosed that as the sound amplitude is varied, other conditions remaining the same, the streaming changes discontinuously through several stable regimes. It appears that in order to account for the generation of vorticity one needs to assume different conditions at the boundaries for each regime. For at least one regime, a theoretical model due to Nyborg seems to be applicable; comparison made with experimentally determined streaming velocities.

The acoustic bubble: Oceanic bubble acoustics and ultrasonic cleaning

“…In contrast, the UAS system projects sound down a column of water [34] in order to excite surface waves [35][36][37] on the walls of microscopic bubbles on the surface to be cleaned. These surface waves can generate convection [38][39][40] and shear forces [1,41,42] in the liquid close to the bubble wall, and so produce a cleaning effect, and alter the way material deposits onto surfaces [43].…”

In-chip direct laser writing of a centimeter-scale acoustic micromixer

“…Typically, these mixers either excite a flow at the sidewalls of a microfluidic chamber [5][6][7] or excite a flow inside the chamber using a bubble. [8][9][10] In the case of homogeneous mixing, the chamber size is limited by the spatial extent of the induced flows, which subsequently limits the flow rate. Bubbles can be placed inside the volume and allow higher throughput compared with sidewall induced flows, enabling fast mixing.…”

LCAT DNA Shearing

“…The frequency and amplitude of the sound field affect the mode of oscillation of the air-liquid interface, which affects the streaming near the bubble. 10,12 The micromixer consists of cavity acoustic transducers (CATs), which are dead-end channels that are placed inside of a chamber or channel, which trap air when a fluid is flowed over the cavities. The application of CATs can be changed depending on the placement of the CATs within a channel, either laterally (lateral cavity acoustic transducer [LCAT]) or vertically (vertical cavity acoustic transducer).…”