Granular material discharge from a flat-bottomed silo has been simulated by using continuum modeling and a three-dimensional discrete-element method (DEM). The predictive abilities of three commonly used frictional viscosity models (Schaeffer, S-S, and mu(I)) were evaluated by comparing them with the DEM data. The funnel-flow pattern (type C) and the semi-mass-flow pattern (type B) that was predicted by DEM simulations can be represented when the Schaeffer or mu(1) model is used, whereas the S-S model gives a consistent type-B flow pattern. All three models over-estimate the discharge rate compared with the DEM. The profiles of the solids volume fraction and the vertical velocity above the outlet show that the larger discharge rates given by the Schaeffer and mu(I) model result from an over-estimation of volume fraction, whereas the deviation in the S-S model stems from the failure to predict a solid vertical velocity and a volume fraction. (C) 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved
