Experimental study of the lower and upper angles of repose of granular materials in rotating drums

The lower and upper angles of repose of glass beads are experimentally investigated in rotating drums at the slumping motion. The drum diameters are 200 mm, 300 mm and 500 mm. Two sizes of glass beads (3 mm, 5 mm) are used. The effect of the rotation speed, the filling degree and the drum diameter on the lower and upper angles is investigated. A correlation between these two angles is obtained based on own measurements and those reported in the literature. The results are useful in practice and in the mathematical modeling of the slumping–rolling transition.