Length and time scales of a liquid drop impact and penetration into a granular layer

Liquid drop impact and penetration into a granular layer are investigated with diverse liquids and granular materials. We use various sizes of SiC abrasives and glass beads as a target granular material. We also employ ethanol and glycerol aqueous solutions as well as distilled water to make a liquid drop. The liquid drop impacts the granular layer with a low speed (similar to ms(-1)). The drop deformation and penetration are captured by a high-speed camera. From the video data, characteristic time scales are measured. Using a laser profilometry system, resultant crater morphology and its characteristic length scales are measured. Static strength of the granular layer is also measured by the slow pillar penetration experiment to quantify the cohesive force effect. We find that the time scales are almost independent of impact speed, but they depend on liquid drop viscosity. In particular, the penetration time is proportional to the square root of the liquid drop viscosity. In contrast, the crater radius is independent of the liquid drop viscosity. The crater radius is scaled by the same form as the previous paper, Katsuragi (Phys. Rev. Lett., vol. 104, 2010, art. 218001).