Hydrodynamical forces acting on particles in a two-dimensional flow near asolid wall

The hydrodynamical forces acting on a single particle and on a random rigid array of particles suspended in a two-dimensional shear flow of Newtonian fluid near a rigid wall were studied numerically in the flow regime where t he relevant Reynolds numbers are of the order of unity. The simulations wer e done with conventional finite volume method for single-particle cases and with lattice-Boltzmann method for many-particle cases. A set of comparison cases was solved with both methods in order to check the accuracy of the l attice-Boltzmann method. For the single-particle case analytic formulae for the longitudinal drag force and for the transverse lift force were found. A modification to Darcy's law is proposed which takes into account the incr ease of the drag force near a moving wall. In the how conditions studied he re, the lift force acting on the particle array was found to be repulsive c lose to the wall, but becomes weakly attractive as the distance from the wa ll is increased. (C) 2000 Elsevier Science B.V. All rights reserved.