COUETTE FLOWS OF A GRANULAR MONOLAYER - AN EXPERIMENTAL-STUDY

An experimental study concerning rapid flows of granular materials in a two-dimensional planar granular Couette flow apparatus is performed. The device is capable of generating particulate flows in the grain-in ertia regime at different shearing rates and solid volume fractions. M ulti-color spherical glass particles are sheared across an annular tes t-section for several wall angular velocities. A video recorder is use d to record the motion of particles and consecutive images are stored and analyzed by an image processing technique for evaluating individua l grain velocities. Experimental data for the mean velocity, the root- mean-square (RMS) fluctuation velocity components and the solid volume fraction profiles an obtained. The resulting mean velocity profiles h ave a roughly linear variation for the range of solid volume fractions and shear rates studied. The solid volume fraction profiles exhibit n on-uniform variations with the highest concentration occurring near th e center of the shearing cell. The RMS fluctuation velocities are roug hly constant, with the streamwise fluctuation being somewhat larger th an the cross-stream direction. The experimentally measured flow proper ties are in reasonable agreement with the earlier theoretical and simu lation results. (C) 1998 Elsevier Science B.V.