The paper focuses on confined silo flow of cohesionless sand. The problem considered is a quasi-static flow in a plane strain model silo with parallel walls simulated with the material point method (MPM). The simulation used a non-local hypoplastic constitutive model. Initially, the paper validated the implemented numerical approach with basic element tests and a plane strain compression test. The subsequent MPM calculations for a model silo were performed with different initial void ratios of sand and silo wall roughness. The flow simulations took also into account the different both location and width of the outlet. The emphasis was on the evolution of both shear zones (wall and internal curvilinear shear zones) and their impact on wall stresses/forces during flow. The numerical findings enhance the understanding of shear localization in granular materials during confined controlled flow in silos and its immense effect on the magnitude and distribution of wall pressures. (C) 2020 Elsevier B.V. All rights reserved.