Rayleigh-Taylor instability on a sonoluminescing gas bubble

Abstract

An air bubble trapped in water emits light stably at its collapse point when a proper forcing amplitude and frequency of ultrasound are applied to the bubble. We used a rigorous analytical treatment to investigate the Bayleigh-Taylor (BT) instability mechanism that causes deviation from sphericity of the wall of the bubble at the collapse point in the sonolumidescence (SL) region. Our study revealed that the RT instability due to bubble wall acceleration occurred when the gas density inside bubble exceeded a certain limit. A lagging motion of bubble relative to the ultrasound due to the viscoelastic behavior of the bubble rather than viscous damping was a crucial parameter in determining the upper threshold of SL. The calculations for the upper limit of the stable sonoluminescence region agreed well with experimental data.