The particle flow in a parallel-hopper bell-less charging apparatus has been studied by the physical experiments and DEM (discrete element method) simulations with mono-sized particles. The contact force chains, flow patterns, velocity distribution, stress distribution and wall pressure during the filling and discharge processes were analyzed numerically. The flow in the parallel-hopper is an asymmetric flow which consists of the quasi stagnant zone, wall shear zone, deflecting flow zone, converging flow zone and the transitional flow zone. The particles in the quasi-stagnant zone, deflecting flow zone and converging flow zone play an important role in inducing the local heterogeneity of particle stresses in hopper. The asymmetry and difference of wall pressure on two side walls were also predicted numerically. The obtained asymmetrical stress distribution during discharge is clearly related to the unsymmetrical flow pattern and velocity distribution in the parallel-hopper as compared to the symmetrical hopper. The influence of the particle-wall sliding friction coefficient and rolling friction coefficient on the wall pressure was analyzed. In addition, the contact force chains within particles were investigated. It is demonstrated that the strong force chains mainly locate at the lower part of the hopper or near the sloping wall, whereas the weak force chains are distributed over the deflected flow zone. (C) 2017 Elsevier B.V. All rights reserved.