Impact of a Liquid Drop on a Granular Medium: inertia, viscosity and surface tension effects on the drop deformation

An experimental study of liquid drop impacts on a granular medium is proposed. Four fluids were used to vary physical properties: pure distilled water, water with glycerol at 2 concentrations 1:1 and 1:2 v/v and water with Tween 20 at the concentration of 0.1g/l. The drop free fall height was varied to obtain a Weber number (We) between 10 and 2000. Results showed that obtained crater morphologies highly depend on the impacting drop kinetic energy E_{K}. Different behaviours during the drop spreading, receding and absorption are highlighted as function of the fluids viscosity and surface tension. Experimental absorption times are also commented and compared with a simplified theoretical model. Drops maximal extensions and craters diameters were found to scale as $We^{1/5}$ and $E_K^{1/5}$ respectively. In both cases, found dependencies are smaller than those reported in literature: $We^{1/4}$ for drop impacts on solid or granular surfaces and $E_K^{1/4}$ for spherical solid impacts on granular media.