Intrusion into Granular Media Beyond the Quasistatic Regime

LK Roth and ED Han and HM Jaeger, PHYSICAL REVIEW LETTERS, 126, 218001 (2021).

DOI: 10.1103/PhysRevLett.126.218001

The drag force exerted on an object intruding into granular media is typically assumed to arise from additive velocity and depth dependent contributions. We test this with intrusion experiments and molecular dynamics simulations at constant speed over four orders of magnitude, well beyond the quasistatic regime. For a vertical cylindrical rod we find velocity dependence only right after impact, followed by a crossover to a common, purely depth-dependent behavior for all intrusion speeds. The crossover is set by the timescale for material, forced to well up at impact, to subsequently settle under gravity. These results challenge current models of granular drag.

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