Peak Force Scaling During Impacts into Wet and Dry Granular Materials*

Impacts into granular materials, both wet and dry, are common in engineering and nature, but a fundamental description of the forces during impact is still lacking. Certain drag laws (e.g., Poncelet laws) and other rheological descriptions (e.g., inertial rheology for dry grains or discontinuous shear thickening for suspensions) are often successful in describing certain aspects of the forces, but these descriptions typically fail to capture the largest forces during the initial moments of impact. Here, we use experiments and simulations to study early time dynamics of impacts into wet and dry granular materials. We show that the magnitude and time scales of the peak forces obey power law scaling that is similar across the different types of materials we study, and we use dimensional analysis to isolate the relevant physical mechanisms. We find that existing models do not predict many of the scaling laws we observe, suggesting the need for new models to describe this process.