Effect of Wall Shear Stress Distribution on Manning Coefficient of Smooth Open Rectangular Channel Flows


Abstract: The determination of velocity distribution in open channel flows is crucial in many critical engineering problems such as channel design, calculation of energy losses and sedimentation. In this study, velocity distribution is experimentally investigated in a smooth rectangular open channel. Wall shear stresses are calculated using measured local velocities. Assuming logarithmic velocity distribution along perpendiculars to a wetted perimeter, dimensionless wall shear stresses K(I) = \tau_w\bar{\tau}_w and A and B constants unique to the cross section in the Prandtl equation were calculated. A correlation for friction coefficient in an open channel is developed using measured wall shear stress distribution. An improved relation for the Manning coefficient on smooth rectangular channels is proposed.

Keywords: Open channel flow, Manning friction coefficient, Wall shear stress.

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