Cationic polyelectrolyte flocculated sewage sludge floes were hung on an elastic nylon stick, and then subjected to a uniform water flow. Their consequent displacements were then measured. The hydrodynamic drag force on the polyelectrolyte flocculated floes was estimated from the measured displacement and the elasticity constant of the stick. These measured results compared favorably with the numerical results yielded using a three-dimensional pore structured model based on real waste activated sludge floe.