Estimation of Friction Factor in Open Channels
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Using a large set of field and laboratory data, this study investigated the effect of slope and the Shields parameter on the friction factor. It identified the ranges of critical shear stress and bed slope for which Froude number would or would not play an important role in the evaluation of friction. It was found that the prediction of friction factor for slopes less than 0.000 81 was not satisfactory. For the Shields parameter range of (0.01< τ*c <0.1) and the range of slope of 0.000 82-0.01, the prediction of friction factor was satisfactory even without considering the effect of Froude number. On the other hand, the inclusion of Froude number improved the estimation of friction factor for the range of (0.01< τ*c <0.05) and steeper slopes (0.01-0.02). Finally, in gravel/sand rivers in Iran, friction factor can be estimated whether or not the flow velocity is known. © 2010 ASCE.
author list (cited authors)
Motamedi, A., Afzalimehr, H., & Singh, V. P.