We probe the dependence of the low-velocity drag force in granular materials on the effective gravitational acceleration (geff) through studies of spherical granular materials saturated within fluids of varying density. We vary geff by a factor of 20, and we find that the granular drag is proportional to geff, i.e. that the granular drag, Fprobe, on a vertical cylinder follows the expected relation Fprobe=ηρgraingeffdprobehprobe2 where the drag is related to the probe's depth of insertion, hprobe; the probe's diameter, dprobe; the grain material's density, ρgrain; and a dimensionless constant, η. The dimensionless constant shows no systematic variation over four orders of magnitude in effective grain weight, demonstrating that the relation holds over that entire range to within the precision of our data.
Physical Review E
- Pub Date:
- January 2011
- Granular flow: mixing segregation and stratification;
- Granular flow;
- Condensed Matter - Soft Condensed Matter
- Phys. Rev. E 83, 011305 (2011) (abstract online at http://pre.aps.org/abstract/PRE/v83/i1/e011305)