Force and flow at the onset of drag in plowed granular media

Gravish, Nick; Umbanhowar, Paul B.; Goldman, Daniel I.

Title:

Force and flow at the onset of drag in plowed granular media

dc.contributor.author	Gravish, Nick
dc.contributor.author	Umbanhowar, Paul B.
dc.contributor.author	Goldman, Daniel I.
dc.contributor.corporatename	Georgia Institute of Technology. School of Physics	en_US
dc.contributor.corporatename	Georgia Institute of Technology. School of Biology	en_US
dc.contributor.corporatename	Georgia Institute of Technology. Institute for Robotics and Intelligent Machines	en_US
dc.contributor.corporatename	Northwestern University (Evanston, Ill.). Department of Mechanical Engineering	en_US
dc.date.accessioned	2014-10-23T16:52:06Z
dc.date.available	2014-10-23T16:52:06Z
dc.date.issued	2014
dc.description	© 2014 The American Physical Society	en_US
dc.description	DOI: 10.1103/PhysRevE.89.042202
dc.description.abstract	We study the transient drag force F[subscript D] on a localized intruder in a granular medium composed of spherical glass particles. A flat plate is translated horizontally from rest through the granular medium to observe how F[subscript D] varies as a function of the medium’s initial volume fraction, φ. The force response of the granular material differs above and below the granular critical state, φ[subscript c], the volume fraction which corresponds to the onset of grain dilatancy. For φ<φ[subscript c] F[subscript D] increases monotonically with displacement and is independent of drag velocity for the range of velocities examined (<10 cm/s). For φ>φ[subscript c], F[subscript D] rapidly rises to a maximum and then decreases over further displacement. The maximum force for φ>φ[subscript c] increases with increasing drag velocity. In quasi-two-dimensional drag experiments, we use granular particle image velocimetry (PIV) to measure time resolved strain fields associated with the horizontal motion of a plate started from rest. PIV experiments show that the maxima in F[subscript D] for φ>φ[subscript c] are associated with maxima in the spatially averaged shear strain field. For φ>φ[subscript c] the shear strain occurs in a narrow region in front of the plate, a shear band. For φ<φ[subscript c] the shear strain is not localized, the shear band fluctuates in space and time, and the average shear increases monotonically with displacement. Laser speckle measurements made at the granular surface ahead of the plate reveal that for φ<φ[subscript c] particles are in motion far from the intruder and shearing region. For φ>φ[subscript c], surface particles move only during the formation of the shear band, coincident with the maxima in F[subscript D], after which the particles remain immobile until the sheared region reaches the measurement region.	en_US
dc.embargo.terms	null	en_US
dc.identifier.citation	Gravish, N., Umbanhowar, P., & Goldman, D. Force and flow at the onset of drag in plowed granular media. Physical Review E, 89(4), 042202 (2014).© 2014 by The American Physical Society.	en_US
dc.identifier.doi	10.1103/PhysRevE.89.042202
dc.identifier.issn	1539-3755 (print)
dc.identifier.issn	1550-2376 (Online)
dc.identifier.uri	http://hdl.handle.net/1853/52722
dc.language.iso	en_US	en_US
dc.publisher	Georgia Institute of Technology	en_US
dc.publisher.original	American Physical Society
dc.subject	Drag force	en_US
dc.subject	Granular materials	en_US
dc.subject	Granular medium	en_US
dc.subject	Localized forcing	en_US
dc.subject	Localized intruder	en_US
dc.subject	Plate drag	en_US
dc.subject	Yield force	en_US
dc.title	Force and flow at the onset of drag in plowed granular media	en_US
dc.type	Text
dc.type.genre	Article
dspace.entity.type	Publication
local.contributor.author	Goldman, Daniel I.
local.contributor.corporatename	College of Sciences
local.contributor.corporatename	School of Physics
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