Revisited analysis of pressure drop in flow through crushed rocks

Experimental data of pressure drop in flow through crushed rocks are reanalyzed with the capillary model in comparison with a model based on the square root of permeability as characteristic length. The capillary model is described by two parameters: the pore diameter and the tortuosity. The comparison leads to relationships between the structural parameters, Reynolds number, and friction factor of each model. The interest of the capillary model is that a single equation can predict all the experimental data expressed in terms of a pore friction factor as a function of pore Reynolds number. The equation, which is the sum of a viscous term and an inertial one, is valid for the whole Reynolds number domain. The equation can be used for the determination of the limits of the Darcy and turbulent flow regimes. According to the criterion used to neglect the viscous or the inertial term,. the flow regimes limits can be expressed by a simple numerical value.