Date of this Version
Physical Review Letters
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.
© 2013 American Physical Society. You can view the original article at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.168002
Brzinski, T. A., Mayor, P., & Durian, D. J. (2013). Depth-Dependent Resistance of Granular Media to Vertical Penetration. Physical Review Letters, 111 (16), 168002-1-168002-5. http://dx.doi.org/10.1103/PhysRevLett.111.168002
Date Posted:10 October 2017
This document has been peer reviewed.