Semi-analytical method to estimate boundary shear stress in smooth rectangular and trapezoidal open channels.

In smooth prismatic open channels, the boundary shear stress is obtained from continuity and momentum equations. The shear stress is a function of gravity, secondary flow and gradient velocity. In this research, semi-analytical equations were developed to estimate the average boundary shear stress in smooth rectangular and trapezoidal open channels with side slopes of 0.5, 1.0, 1.5 and 2.0 using conformal mapping techniques. After dividing the channel cross-section into bed and wall sub-sections, a previously presented method was used to estimate the average shear stress of the bed and the wall in open channels. For the studied case, in the first estimate of shear stress, the secondary current and constant eddy viscosity were neglected. After determining correction factors for secondary currents and eddy viscosity, the second estimation provided a good match with experimental measurements of the average shear stress for all aspect ratios. [ABSTRACT FROM AUTHOR]