An experimental study on hydraulic behavior of free-surface radial flow in coarse-grained porous media

The equations of fluids in porous media are very useful in designing the rockfill and diversion dams, gabions, breakwaters and ground water reserves. Researches have been showed that the Forchheimer equation is not sufficient for the analysis of hydraulic behavior of free-surface radial flows; because, in these flows, in addition to the hydraulic gradient and velocity, the variable of radius is also an independent parameter due to variations in cross section. In this paper, we have used an experimental model to analyze the nonlinear free surface radial flows and to introduce an equation compliant with these flows. This is a semi cylindrical model including a type of coarse grained aggregate which leads the radial flow into the center of a well. Thereafter, the hydraulic gradient was measured on different points of the experimental model by three distinguished methods of difference of successive radii, keeping constant the minimum and maximum radii. An equation, describing the behavior of free surface radial flow, was then proposed by measured data (as regression data) from the laboratory and analysis of the results. Verification of the proposed equation by test data shows that the equation is valid on the established limits of the data.