Relaxation behavior of microbubbles in ultrasonic field

Abstract

The nonlinear oscillation of microbubbles under the influence of ultrasound was investigated experimentally and theoretically. The radius-time curves of bubbles including afterbounces calculated using the Rayleigh-Plesset equation with polytropic relations and with the Keller-Miksis equation using analytical solutions for the Navier-Stokes equations of the gases were compared with the results observed from light scattering. This study revealed that the dynamic behavior of microbubbles in an ultrasonic field, such as the expansion ratio of the maximum to the equilibrium radius and the bouncing motion after the first collapse (minimum), depends crucially on the relaxation time of the bubble motion with respect to the characteristic time of the applied ultrasound. and that the relaxation time decreases as the equilibrium radius of the microbubbles increases.