Estimation of Friction Coefficient in Sediment Contained Flow through Rockfill

An increase in the flow velocity in flow through large porous media and deflection of flow regime from Darcy law causes a nonlinear relationship between hydraulic gradient and pore velocity of media.One of the most important subjects in flow through large porous media is relationship between frictioncoefficient and flow characteristics which was previously focused by some investigators but it is needed to extract general and more accurate relationships for all of their data series. Also, in most of previous studies the friction coefficient was presented in Darcy-Weisbach form which is not socommon in the open channel flow between hydraulic engineers like Manning coefficient. In this study, the required data were collected from four different sources. Three series of them were operated in the sediment contained flowthrough mode and another one was operated in sediment free flowthroughmode. Using some basic equations about pore velocity and frictional coefficient, the new relationshipswere developed and calibrated for estimation of manning coefficient in open channel fow throughporous media. It was found that modified Wilkins equation had a better estimation for manningcoefficient in both sediment free and sediment 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 flow through 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

کلیدواژه ها:

Non-Darcy Flow ، Sediment Contained Flowthrough ، Friction Coefficient