Emergence of superwalking droplets

Rahil N. Valani, Jack Dring, Tapio P. Simula, Anja C. Slim

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1 Citation (Scopus)

Abstract

A new class of self-propelled droplets, coined superwalkers, has been shown to emerge when a bath of silicone oil is vibrated simultaneously at a given frequency and its subharmonic tone with a relative phase difference between them (Valani et al., Phys. Rev. Lett., vol. 123, 2019, 024503). To understand the emergence of superwalking droplets, we explore their vertical and horizontal dynamics by extending previously established theoretical models for walkers driven by a single frequency to superwalkers driven by two frequencies. Here, we show that driving the bath at two frequencies with an appropriate phase difference raises every second peak and lowers the intermediate peaks in the vertical periodic motion of the fluid surface. This allows large droplets that could otherwise not walk to leap over the intermediate peaks, resulting in superwalking droplets whose vertical dynamics is qualitatively similar to normal walkers. We find that the droplet's vertical and horizontal dynamics are strongly influenced by the relative height difference between successive peaks of the bath motion, a parameter that is controlled by the phase difference. Comparison of our simulated superwalkers with the experiments of Valani et al. (2019) shows good agreement for small-to moderate-sized superwalkers.

Original languageEnglish
Article numberA3
Number of pages28
JournalJournal of Fluid Mechanics
Volume906
DOIs
Publication statusPublished - 9 Nov 2020

Keywords

  • capillary waves
  • drops
  • Faraday waves

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