THEORETICAL PREDICTION OF STRESS AND VELOCITY PROFILES IN CONICAL HOPPERS

Stress and velocity profiles have been predicted for a granular material undergoing mass flow in a conical hopper, by solving the radial stress field equations. By using various permutations of yield function and flow rule, it is shown that previously observed differences in the prediction of flowing zone angles are the result of the value assumed for the azimuthal stress component. The choice of yield function is demonstrated to have negligible influence on the predicted stress or velocity profiles. A comparison of predicted and experimentally measured velocity profiles clearly gives support to theories that use the levy flow rule to equate the magnitudes of the azimuthal and tangential stress components. Doubt is therefore cast on the established hypothesis of Haar and von Karman.