Flow field distributions of discharging various sized granular materials from wedge-shaped feed hopper was numerically simulated using three-dimensional discrete element method. A mathematical model of mass flow index (MFI) was proposed for the wedge-shaped feed hopper. The discharge flow pattern and its relationship with discharge mass flow rate was analyzed

and model reliability was verified experimentally. The results show that granular flow field in the hopper has a high velocity region near feed pipe outlet and is radially attenuated towards low velocity region at the upper hopper which is away from vertical wall and feed pipe. The flow direction of particles in high velocity region was well consistent

whereas granular flow in low velocity region exhibited local vortices. With the increase of particle size

overall flowability of particles in the hopper decreased

which high velocity region shrinked

low velocity region enlarged

and transition region became obscure

hence both MFI and discharge mass flow rate were decreased. When particle size was no more than 10 mm

MFI was negatively linearly related to particle size

but was positively linearly to discharge mass flow rate.