DRIVEN AND FREELY DECAYING NONLINEAR SHAPE OSCILLATIONS OF DROPS AND BUBBLES IMMERSED IN A LIQUID - EXPERIMENTAL RESULTS

Large-amplitude oscillations of drops and bubbles immersed in an immis cible liquid host have been investigated using ultrasonic radiation pr essure techniques. Single levitated or trapped drops and bubbles with effective radius between 0.2 and 0.8 cm have been driven into resonant shape oscillations of the first few orders. The direct coupling of dr iven drop shape oscillations between the axisymmetric l = 6 and l = 3 modes has been documented as well as the interaction between axisymmet ric and non-axisymmetric I = 3 and I = 2 modes. Effective resonant ene rgy transfer from higher- to lower-order modes has been observed toget her with a much less efficient energy transfer in the reverse directio n. The first three resonant modes for bubbles trapped in water have al so been excited, and mode coupling during driven and free-decaying osc illations has been measured. The evidence gathered thus far indicates that efficient drop resonant coupling between a higher- and a lower-or der mode occurs when the characteristic frequency of the latter mode r oughly coincides with a harmonic resonance.