Flow of wet granular materials.
The transition from frictional to lubricated flows of a dense suspension of non-Brownian particles is studied. The pertinent parameter characterizing this transition is the Leighton number Le=eta(s)gamma / sigma, the ratio of lubrication to frictional forces. Le defines a critical shear rate below which no steady flow without localization exists. In the frictional regime the shear flow is localized. The lubricated regime is not simply viscous: the ratio of shear to normal stresses remains constant and the velocity profile has a universal form in both frictional and lubricated regimes. Finally, a discrepancy between local and global measurements of viscosity is identified, which suggests inhomogeneity of the material under flow.
Huang
N
N
Laboratoire de Physique Statistique, UMR 8550 CNRS, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France.
Ovarlez
G
G
Bertrand
F
F
Rodts
S
S
Coussot
P
P
Bonn
Daniel
D