Scaling of liquid-drop impact craters in wet granular media

TL;DR

This study investigates how liquid-drop impacts create craters in wet granular media, revealing a new scaling law based on impact energy, drop size, and saturation, and emphasizing the role of compressive stresses.

Contribution

It introduces a novel scaling law for impact crater size in wet granular media and explains it through a balance of inertia and surface strength, extending understanding from dry to wet conditions.

Findings

A new impact crater size scaling law for wet granular media

Impact craters are governed by compressive stresses rather than shear stresses

The energy partition model applies to wet granular impact cratering

Abstract

Combining high-speed photography with laser profilometry, we study the dynamics and the morphology of liquid-drop impact cratering in wet granular media---a ubiquitous phenomenon relevant to many important geological, agricultural, and industrial processes. By systematically investigating important variables such as impact energy, the size of impinging drops and the degree of liquid saturation in granular beds, we uncover a novel scaling for the size of impact craters. We show that this scaling can be explained by considering the balance between the inertia of impinging drops and the strength of impacted surface. Such a theoretical understanding confirms that the unique energy partition originally proposed for liquid-drop impact cratering in dry granular media also applies for impact cratering in wet granular media. Moreover, we demonstrate that compressive stresses, instead of shear stresses, control granular impact cratering. Our study enriches the picture of generic granular impact cratering and sheds light on the familiar phenomena of raindrop impacts in granular media.