Single Bubble Sonoluminescence and Bubble Surface Stability in Surfactant Solutions

摘要

The radial dynamics of a single sonoluminescing bubble has been investigated in surfactant solutions. Experimental results show that an increase in the surfactant concentration leads to a decline in the oscillation amplitude and hence light emission intensity. Numerical simulations support this result, showing that under the driving pressures required to achieve single bubble sonoluminescence (SBSL), the surface properties, namely the surface elasticity and dilatational viscosity, contribute to the damping of the radial amplitude in the bubble oscillation. In most cases this stabilises the bubble surface, but leads to a decreased light intensity due to smaller oscillation amplitude. The application of a stronger driving pressure in an attempt to produce equivalent light emission to a surfactant-free bubble, leads to a decrease in the surface stability, making it practically very difficult for a bubble to achieve high SBSL intensities in concentrated surfactant solutions. Although the bubble oscillates at a smaller amplitude, the instability mechanism for a surfactant-coated bubble at higher ambient radii and surfactant concentrations, is more likely to be of the Rayleigh-Taylor type than that of a clean bubble at the same given acoustic parameters. This can lead to bubble disintegration before correcting mechanisms can bring the bubble back into the stable SL regime.