Estimation of Friction Coefficient in Sediment Contained Flow through Rockfill

Abstract

An increase in the flow velocity in flowthrough large porous media and deflection of flow regime from Darcy law causes a nonlinear relationship between hydraulic gradient and pore velocity of media. So many investigations have done previously in such Medias. One of the most important subjects in flowthrough large porous media is relationship between friction coefficient and flow characteristics which previously focused by some of investigators. On the other hands, most of the structures which are generated from such media like detention rockfill dams convey sediment contained flow. Therefore a detailed investigation is needed to study relationship between friction coefficient and flow characteristics in the sediment contained flowthrough. Also in most of previous studies the friction coefficient presented in Darcy-Weibach form which is not so common in the open channel flow between hydraulic engineers like manning coefficient. In this study required data was collected from four different sources. Three series of them were operated in the sediment contained and another one was operated in sediment free flowthrough mood. By using some basic equations about pore velocity and frictional coefficient new relationships were developed and calibrated for estimation of manning coefficient in open channel fowthrough porous media. It was found that modified Wilkins equation has a better estimation for manning coefficient in both of sediment free and contained flow rather than Ergun and Sedghi’s one. Also it was found that general trend of moody diagram for pipe flow is established in flowthrough large porous media such that by increase in the media Reynolds number, the manning coefficient limits to a constant value and become dependent to the media characteristics.