Department of Physics Papers

Document Type

Journal Article

Date of this Version

10-18-2013

Publication Source

Physical Review Letters

Volume

111

Issue

16

Start Page

168002-1

Last Page

168002-5

DOI

10.1103/PhysRevLett.111.168002

Abstract

We measure the quasistatic friction force acting on intruders moving downwards into a granular medium. By utilizing different intruder geometries, we demonstrate that the force acts locally normal to the intruder surface. By altering the hydrostatic loading of grain contacts by a sub-fluidizing airflow through the bed, we demonstrate that the relevant frictional contacts are loaded by gravity rather than by the motion of the intruder itself. Lastly, by measuring the final penetration depth versus airspeed and using an earlier result for inertial drag, we demonstrate that the same quasistatic friction force acts during impact. Altogether this force is set by a friction coefficient, hydrostatic pressure, projectile size and shape, and a dimensionless proportionality constant. The latter is the same in nearly all experiments, and is surprisingly greater than one.

Copyright/Permission Statement

© 2013 American Physical Society. You can view the original article at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.168002

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Date Posted:10 October 2017

This document has been peer reviewed.