Flow-induced agitations create a granular fluid.
We fluidize a granular medium through localized stirring and probe the mechanical response of quiescent regions far away from the main flow. In these regions the material behaves like a liquid: high-density probes sink, low-density probes float at the depth given by Archimedes' law, and drag forces on moving probes scale linearly with the velocity. The fluidlike character of the material is set by agitations generated in the stirred region, suggesting a nonlocal rheology: the relation between applied stress and observed strain rate in one location depends on the strain rate in another location.
Nichol
Kiri
K
Kamerlingh Onnes Lab, Universiteit Leiden, Postbus 9504, 2300 RA Leiden, The Netherlands.
Zanin
Alexey
A
Bastien
Renaud
R
Wandersman
Elie
E
van Hecke
Martin
M