Rayleigh-Taylor Instability Mechanism on Sonoluminescing Bubble

Air bubble trapped in water emits light stably at its collapse point when proper forcing amplitude and frequency of ultrasound are applied to the bubble. We investigated the Rayleigh-Taylor instability mechanism that causes deviation from sphericity of wall of the bubble at the collapse point in the sonoluminescence (SL) regime with rigorous analytical treatment. Our study revealed that the RT instability due to the bubble wall acceleration occurs when the gas density inside bubble exceeds a certain limit. Lagging motion of bubble to the ultrasound due to the viscoelastic behavior of bubble rather than viscous damping was a crucial parameter in determining the upper threshold of SL. The calculation results for the upper limit of stable sonoluminescence regime agreed well with experimental data.