Low Speed Oblique Impact Behavior On Granular Media Across Gravitational Conditions; The role of cohesion

TL;DR

This study investigates how cohesion influences low-speed oblique impacts on granular media across different gravitational conditions, highlighting the need for new scaling laws to accurately model these interactions.

Contribution

It introduces numerical and analytical models to analyze cohesion effects on impact behavior under various gravity levels, revealing limitations of existing scaling approaches.

Findings

Cohesion effects are more significant at lower gravity levels.

Existing models inadequately account for cohesion's role in impact dynamics.

New dimensionless parameters are needed for accurate scaling of cohesion effects.

Abstract

Analyses of impact provide rich insights from the evolution of granular bodies to their structural properties of the surface and subsurface layers of celestial bodies. Although chemical cohesive bonding has been observed in asteroid samples, and low-speed impact has been a subject of many studies, our understanding of the role of cohesion in these dynamics is limited, especially at small gravities such as those observed on asteroid surfaces. In this work, we use numerical discrete element method (DEM) and analytical dynamic resistive force theory (DRFT) modeling to examine the effect of cohesion on the outcome of the impact into loose granular media and explore scaling laws that predict impact behavior in the presence of cohesion under various gravitational conditions and cohesive strengths. We find that the effect of cohesion on the impact behavior becomes more significant in smaller gravitational acceleration, raising the need to scale the cohesion coefficient with gravity. We find that due to an insufficient understanding of confounding between cohesion and friction-induced quasi-static and inertial resistance, the outcomes of the DEM simulation models are incongruent with a suggested analytic model using Froude and Bond number scaling based on an additive contribution of frictional and inertial forces. Our study suggests that new dimensionless parameters and scaling are required to accurately capture the role of cohesion, given its ties to frictional behavior between the grain particles at different gravities.