We develop a computational fluid dynamics (CFD) model for describing the hydrodynamics of sieve frays. The gas and liquid phases are modelled in the Eulerian framework as two interpenetrating phases. The interphase momentum exchange (drag) coefficient is estimated using the Bennett et al. (1983) correlation as basis. Several three-dimensional transient simulations were carried out for a 0.3 m diameter sieve tray with varying superfical gas velocity, weir height and liquid weir loads. The simulations were carried out using a commercial code CFX 4.2 of AEA Technology, Harwell, UK and run on a Silicon Graphics Power Challenge workstation with six R10000 200 MHz processors used in parallel. The CFD simulations reflect chaotic tray hydrodynamics and reveal several liquid circulation patterns, which have true three-dimensional character. The clear liquid height determined from these simulations is in good agreement with the Bennett correlation. It is concluded that CFD can be a powerful tool for modelling and design of sieve trays. (C) 2000 Elsevier Science S.A. All rights reserved.