Flow characteristics and discharge rate of ellipsoidal particles in a flat bottom hopper

Hopper flow characteristics are significantly affected by particle shape. In this work, ellipsoidal particles which can represent a large number of shapes are used to investigate the shape effect on granular flow in a cylindrical hopper. Numerical experiments are conducted by use of the discrete element method, with its validity verified by comparison with the results from physical experiments. The results indicate that particle shape can make a significant effect on the flow pattern. In particular, the increase of deviation from spheres can decrease the mixed region adjacent to the side wall, and increase the stagnant zone at the bottom corner. It may also lead to decreased wall stress. Furthermore, particle shape has a significant effect on the discharge rate. Spheres of unity aspect ratio have the highest flow rate, and the lower or higher aspect ratio, the smaller the flow rate. Based on the numerical results, the Beverloo equation is modified, where parameters C and k in the equation are respectively formulated as a function of aspect ratio.