A discrete-element method (DEM) was applied to analyze the complicated phenomena of granular screening using different plate-, bead-, and woven-mesh structures. In the past, mesh structures have often been simplified as plate or bead structures in screening-process simulations, resulting in large differences between the simulated and experimental sieving rate. Here, a mesh-type, 3D woven structure was accurately modeled, and the simulated sieving process yielded results more closely resembling the experimental process. The woven-mesh model constructed of sine and cosine functions was also used to assess the effect of the structures on the sieving rate and mesh-blocking phenomena, i.e., cohesionless particles plugging the mesh. By monitoring the in situ blocking conditions in the discrete-element method simulation, cohesionless particles with diameters of 1.1w (where w is the size of the aperture) were found to block the most mesh apertures. The large difference in sieving rates observed when separating particles with sizes of 0.7w and 1.1w and those of 0.9w and 1.1w resulted from the differing degree of freedom for the smaller particles to move to the bottom of the bed. The 0.7w particles were more able to move downward in the bed and be sieved out, leading to a higher sieving rate as compared to those with 0.9w diameters. The significant factors and phenomena of the sieving process, such as particle-mesh and particle-particle interactions, instantaneous mesh-blocking, and the intrinsic motion of the granular bed, which cannot be observed experimentally, can be modeled by the DEM simulation using our 3D woven-mesh model. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 918-928, 2011