We present here a detailed granular flow characterization together with force measurements for the quasi-bidimensional situation of a horizontal cylinder penetrating vertically at a constant velocity in dry granular matter between two parallel glass walls. In the velocity range studied here, the drag force on the cylinder does not depend on the velocity V0 and is mainly proportional to the cylinder diameter d. While the force on the cylinder increases with its penetration depth, the granular velocity profile around the cylinder is found to be stationary with fluctuations around a mean value leading to the granular temperature profile. Both mean velocity profile and temperature profile exhibit strong localization near the cylinder. The mean flow perturbation induced by the cylinder decreases exponentially away from the cylinder on a characteristic length λ that is mainly governed by the cylinder diameter for a large enough cylinder/grain size ratio d/dg: λ∼d/4+2dg. The granular temperature exhibits a constant plateau value T0 in a thin layer close to the cylinder of extension δT0∼λ/2 and decays exponentially far away with a characteristic length λT of a few grain diameters (λT∼3dg). The granular temperature plateau T0 that scales as V02dg/d is created by the flow itself from the balance between the "granular heat" production by the shear rate V0/λ over δT0 close to the cylinder and the granular dissipation far away.
|Journal||Physical Review E - Statistical, Nonlinear, and Soft Matter Physics|
|State||Published - 10 Jan 2013|