Computational fluid dynamics is used to describe both wetting efficiency in simple configurations of stacked solid particles and catalyst efficiency inside such partially wetted catalyst particles. The volume of fluid (VOF) model used to describe hydrodynamics leads to realistic and promising results for surface wetted ratio. Catalyst efficiency simulations have been performed for different shapes of particles and different Thiele modulus values for a first order reaction rate. Results show that for all the shapes studied, catalyst efficiencies of partially wetted particles can be calculated by simply using a modified Thiele modulus defined as ratio of the actual Thiele modulus phi to the wetting efficiency f. (C) 2009 Elsevier Ltd. All rights reserved.