Impact craters: experiments with Carbopol and non-Newtonian simulations

The impact of drops or solid spheres on solid surfaces, fluid films, or deep pools are processes widely studied using Newtonian fluids and granular media, and less often non-Newtonian fluids. The present work is motivated by planetary impact cratering, a geological process that shapes the surface of planetary bodies. In this process the strength of the impactor and target plays a role in the morphology and scale of the resulting crater. Our experiments use Carbopol gel, a yield-stress fluid, for both the spherical impactor and the target pool. We employ a high-speed camera to record the cavity evolution through a transparent cubic tank following impact. Studying the transient part of the process, we find an energy balance of kinetic, potential, elastic and yield energy and using these findings we explain the size and shape of the transient cavities. Simulations are performed using OpenFOAM with the aim of reproducing the experimental impacts using non-Newtonian fluid models. By varying the models’ parameters, we explore the influence of each of them on the resulting craters. By comparing these results with the experimental ones we disentangle the complex nature of the material we use.