Oscillations, Waves, and Interactions - GWDG

The single bubble – a hot microlaboratory 147
Figure 7. Photographic series of a trapped sonoluminescing bubble driven at 21.4 kHz.
Time between frames: 500 ns, frame size: 160 µm by 160 µm. As the bubble oscillates very
stably, the images were taken one by one (exposure time 5 ns) with increasing delay and
assembled into the series lateron.
black on a brighter background as the illuminating light is deflected off the bubble
surface. A slow growth of the bubble and a fast collapse with several afterbounces
are observed. From the photographic images the varying radius of the bubble can be
measured and compared with theoretical models of bubble oscillation. Figure 8 shows
a comparison for a bubble trapped in a water-glycerine mixture driven at 21.4 kHz
and 132 kPa (measured values). The data input to the Gilmore model are: ambient
pressure p0 =100 kPa, vapour pressure pv =0 kPa, equilibrium radius Rn =8.1 µm,
density of the liquid ρ =1000 kg/m 3 , viscosity µ =0.0018 Ns/m 2 (measured) and surface
tension σ =0.0725 N/m. The gas within the bubble is assumed to obey the
adiabatic equation of state for an ideal gas with κ =1.2. A quite good fit could be
achieved even for the first three afterbounces, except for the strong collapse where
data are missing.