The discharge of regular noncircular particles through a hopper orifice is simulated by discrete element method. A novel approach of incorporating distributed sub-spheres around the non-spherical particle borders is developed. The aim of this work is to explore the effect of roundness on the discharge behavior as well as relevant mechanisms of hopper discharge. Seven types of non-spherical particles, i.e. triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal and decagonal shaped particles, are chosen for comparative study. They are respectively discharged freely from the hopper beds of three different base angles, i.e. alpha = 65, 70 and 75 degrees. The discharge process, fraction, flow rate, and voidages are analyzed to show the effect of particle roundness on discharge characteristics. (C) 2016 Elsevier B.V. All rights reserved.