Low viscous droplets bouncing on a vibrated high viscous bath

Bouncing mechanisms of a droplet on a vertically vibrating high viscous bath are investigated experimentally. The minimal acceleration required for bouncing is measured as a function of the forcing frequency for various viscosities and sizes of the droplet. An analytical model is developed in order to explain the bouncing phenomenon and the obtained acceleration threshold curves. The droplet deformation is shown to play a key role in the process. A large low viscous droplet can experience a cascade of partial coalescences until it reaches a size suitable for bouncing. The vibrated bath works in the same way as a sieve : the experimentalist selects only droplets smaller than a critical size.