The paper deals with modeling the evolution of flow zones during discharge of cohesionless granular materials from bins. A particular kinematic model presented by Waters and Drescher [Powder Technol. 113 (2000) 168] is revised to incorporate the presence of the funnel flow zone, and the effect of stresses developing during flow. The stresses are determined by means of the method of slices widely used in bin-loads analysis; the latter method is extended to the case of plug/funnel flow bins. The source of numerical instability of the equations given in the original model is analyzed, and remedial measures are introduced. The revised model predictions are compared with results of small-scale model tests on semicylindrical and plane, flat-bottomed bins. Good agreement between the model and experiments is demonstrated. (C) 2004 Elsevier B.V. All rights reserved.