Sloshing Resonance of an Acoustically Levitated Air-in-Liquid Compound Drop.

An acoustically levitated air-in-liquid compound drop is set into an out-of-phase azimuthal sloshing resonance by a modulated frequency with modes n = 4-9. Waveforms of the inner and outer liquid-air interfaces conform to the classical Saffren model. Resonance peaks and their harmonics in the frequency spectrum are found to be a function of drop dimension and resonance modes. Drops with multiple small air bubbles do not resonate in sync because of asymmetry. This work has significant implications in the dynamics of core-shell compound drops.