Measurements of the Growth of Air Bubbles by Rectified Diffusion
NAVAL ACADEMY ANNAPOLIS MD MICHELSON PHYSICAL LAB
Pagination or Media Count:
Measurements are reported of the growth of air bubbles by rectified diffusion at 21.6 kHz. Values of the threshold acoustic pressure amplitude were obtained as a function of bubble radius and liquid surface tension and show good agreement with theory. Measurements of the rate of growth of bubbles by rectified diffusion as a function of acoustic pressure amplitude for varying surface tension show agreement only for high surface tension. When the surface tension is lowered by the addition of a surfactant, the observed growth rates become much larger than predicted. Surface wave activity that could increase the growth rate by acoustic streaming was not observed at low radii and was discounted as the responsible mechanism. A possible explanation for the large growth rates is given in terms of a retardation of outward gas diffusion by an organic monolayer present on the surface of the air bubble.
- Fluid Mechanics