Fixed beds of plate shape particles have been studied in two different "flow-particle" configurations. From pressure drop measurements performed for a Newtonian fluid flow, two characteristic structural parameters have been determined by using a capillary-type model. The differences concerning the hydrodynamic behaviour of the two configurations are discussed and a factor characterizing the bed anisotropy is proposed, A dimensionless equation allowing the pressure drop determination for Newtonian and non-Newtonian purely viscous fluid flow in the two configurations, for a large range of Reynolds numbers, is proposed and tested with experiments.