Onset of low-frequency capillary waves driven by high-frequency ultrasound

High frequency thickness mode ultrasound is an energy-efficient way to atomize high-viscosity fluid at high flow rate into fine aerosol mists of micron-sized droplet distributions. However the complex physics of the atomization process is not well understood. It is found that with low power the droplet vibrates at low frequency (O[100 Hz]) when driven by high-frequency ultrasound (O[1 MHz] and above). To study the mechanism of the energy transfer that spans these vastly different timescales, we ...