Session BP - Bubbles II.
ORAL session, Sunday morning, November 19
Congressional E, Hyatt Regency Capitol Hill
The shape stability of spherical microbubbles undergoing violent volume oscillations is considered, with special attention to the gas dynamics in the bubble interior. In his classical analysis Plesset (1954) assumed the gas to be of constant density. While this is a reasonable approximation in cases of mild forcing, it is questionable under intense conditions such as in a sonoluminescence (SL) bubble. The present work is based on a more realistic spherically symmetric base flow, about which nonspherical disturbances evolve. Two types of instability are examined: parametric, which occurs over a number of acoustic cycles (micro seconds), and Raleigh-Taylor, which occurs on a much shorter time scale (nano seconds). It is found that the interior gas dynamics is indeed negligible for analysis of parametric instability, but constitutes a stabilizing influence on the Rayleigh-Taylor instability. Furthermore, with respect to the parameter space of SL, it is argued that the Rayleigh-Taylor stability boundary coincides closely with a mass exchange equilibrium curve associated with constant far-field concentration of dissolved noncondensible gas.