Impact of a liquid drop on a granular medium: Inertia, viscosity and surface tension effects on the drop deformation

Abstract

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 −1 . The drop free fall height was varied to obtain a Weber number (W e) 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 W e 1 5 and E 1 5 K respectively. In both cases, found dependencies are smaller than those reported in literature: W e 1 4 for drop impacts on solid or granular surfaces and E 1 4 K for spherical solid impacts on granular media.

Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes

“…Plotting D c versus E reveals a power-law scaling with an exponent of 0:17 ± 0:01 (Fig. 3A), consistent with Nefzaoui and Skurtys's result (20). This scaling is visibly different from the 1/4 power-law scaling associated with the impact craters created by low-speed solid spheres.…”

“…Instead, Katsuragi argued that the power arises from the scaling of the maximal spreading diameter of the impinging drop, which coincidently follows the same 1/4 scaling with E (22). However, a later study by Nefzaoui and Skurtys showed that D c is not equal to the maximal spreading diameter and a different scaling with D c ∼ E 0:18 was found (20). Although covering a larger dynamic range of E, Nefzaoui and Skurtys only investigated the scaling dependence on E and failed to provide a full scaling for D c .…”

“…Although several recent experiments have been attempted to investigate the morphology of liquid-drop impact craters (17-21), a coherent picture for describing various features of the impact craters is still lacking. Even for the most straightforward impact-energy (E) dependence of the size of liquid-drop impact craters, the results remain controversial and incomplete (17,19,20). Katsuragi (17) and Delon et al (19) reported that the diameter of liquid-drop impact craters D c scales as the 1/4 power of the Weber number of liquid drops, which yields D c ∼ E 1=4 , quantitatively similar to the energy scaling for low-speed solid-sphere impact cratering (10, 11).…”

Aerosol generation by raindrop impact on soil

“…In this work we consider droplets hitting dry soil, which is both wettable and firm enough to maintain its porous structure during the impingement. When droplets have an impact on powder surfaces or granular layers [40][41][42][43][44] , we did not observe bubble formation during the drop impingement. We speculate that if the porous media deform considerably during impact there are low permeability paths for air to escape from beneath the droplet and so it is not trapped.…”

The impact of raindrops on sand

“…It is only in the last decade, that drop impact on sand started to draw the attention of physicists, with studies focused on rain showers [12,13] or single drop impact [14][15][16][17][18][19][20][21].…”