HYDRODYNAMIC DRAG FORCE EXERTED ON A HIGHLY POROUS SPHERE MOVING TOWARDS AN IMPERMEABLE PLATE

This study numerically evaluates the hydrodynamic drag force exerted o n a porous sphere moving through a Newtonian fluid towards an impermea ble flat plate at a Reynolds number ranging from 0.1 to 40. The sphere is assumed to be highly porous, whose interior flow field is modeled by the combined Darcy-Brinkman model. The surrounding fluid how field is governed by steady-state Navier-Stokes equations. When the flee per meability is rather high, which is common for sludge flocs, no boundar y layer separation occurs in the after-sphere region at large Reynolds numbers. The drag force thereby adheres to a Stokes' law like relatio nship. (C) 1998 Elsevier Science Ltd. All rights reserved.