Where are the hot bubbles?

Abstract

To contribute significantly, e.g., to sonoluminescence light emission, bubbles oscillating in an ultrasonic field have to persist for some time that is large compared to the acoustic driving period. This is the case if they are stable against perturbations of shape or position, and do not dissolve or grow too quickly by rectified diffusion. For noble-gas filled bubbles in water with parameters in the corresponding parameter region called bubble habitat, the peak temperatures at collapse are calculated using a standard ODE model of bubble dynamics, assuming homogeneous adiabatic compression of the gas-vapor mixture. Results are presented in terms of phase diagrams with the bubble’s rest radius, driving frequency, acoustic and static pressure, and gas concentration as control parameters. Hot bubbles are encountered in the giant response at high pressures and small bubble size. For such microbubbles, the assumption of homogeneity is tested by molecular dynamics simulations.