Abstract
The enhancement in the rate of bubble growth via rectified diffusion in surfactant solutions during acoustic cavitation has been investigated. Dodecyl trimethyl ammonium chloride (DTAC) caused a greater increase in the growth rate than equivalent concentrations of the surfactants sodium dodecyl sulphate (SDS) and dodecyl dimethyl ammonium propane sulfonate (DDAPS). However, if the electrostatic charge was suppressed by the addition of salt, DDAPS showed the highest growth rate. Particle-image velocimetry (PIV) has been used to characterize the microstreaming around a bubble in aqueous solutions of these surfactants. Results indicate an enhancement of microstreaming velocities in the vicinity of the bubble when surfactant of any form is present in the solution and the results correlate with the enhanced bubble growth rates. A clear difference can also be observed when bubbles undergo surface mode oscillations that dramatically increase the streaming velocities, resulting in a chaotic flow.
