Pressure drops through batches of apples and chicory roots were measured. The results were correlated by means of Darcy-Forchheimer equations. The equations were modified to incorporate the effect of shape, surface roughness and confinement based on physical considerations. The confinement parameters were determined by means of computational fluid dynamics (CFD) simulations of confined beds by means of the Brinkman-modified Ergun equation. The confined pressured drop fitted the experimental data much better than the basic Ergun equation for packings of infinite dimensions. The differences in pressure drop between chicory root beds of different alignment with the airflow and with or without the presence of soil were explained by the relative contribution of surface friction and particle drag. (C) 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.