Dynamics of a dry-rebounding drop: observations, simulations, and modeling

Dynamics of a dry-rebounding drop was studied experimentally, numerically, and theoretically. Experimental results were reproduced by our computational fluid dynamics simulations, from which time series of kinetic energy, potential energy, and surface energy were obtained. The time series of these energies quantitatively clarified the energy conversion and loss during the dry-rebound. These results were interpreted by using an imaginary spring model and a spherical harmonic analysis. The spring model explained the vertical deformation of the drop, however, could not completely explain the energy loss, the timings of the energy loss did not match. From a viewpoint of the spherical harmonic deformation of a drop, the deformation of the drop after the impact was found to be a combination of two vibrational motions. One of the two vibrational motions is an inertial motion derived from the free-fall and the another is a pressure-induced motion derived from a pressure surge due to the sudden stop of the bottom part of the drop at the impact. The existence of the pressure surge at the impact was confirmed in the simulated results. The pressure-induced motion resists the inertial motion and consequently dumps the kinetic energy of the drop.