title: Measurements of grain motion in a dense, three-dimensional granular fluid.
abstract: We have used an NMR technique to measure the short-time, three-dimensional displacement of grains in a system of mustard seeds vibrated vertically at 15 g. The technique averages over a time interval in which the grains move ballistically, giving a direct measurement of the granular temperature profile. The dense, lower portion of the sample is well described by a recent hydrodynamic theory for inelastic hard spheres. Near the free upper surface the mean free path is longer than the particle diameter and the hydrodynamic description fails.
authors.affiliation: Physics Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Huan
authors.forename: D
authors.initials: D
authors.lastname: Candela
authors.forename: R W
authors.initials: RW
authors.lastname: Mair
authors.forename: R L
authors.initials: RL
authors.lastname: Walsworth