Constant speed penetration into granular materials: drag forces from the quasistatic to inertial regime

Predicting the force exerted on an object as it penetrates a granular medium is of interest in engineering, locomotive, and geotechnical applications. Current models drag, however, vary widely applicability parameterization, physical origin resistive itself subject debate. Here we perform constant speed penetration experiments, combined with calibrated, large-scale molecular dynamics simulations, at velocities up to 2 m/s test effect impact velocity depth dependent ‘hydrostatic’ drag force. We discover that evolution flow field around intruder regulates presence forces. In addition, find observed linear dependence commensurate mass flowing grains. These results suggest that, increases beyond quasistatic regime, term becomes intertwined inertial effects.