Boundary shear in circular pipes running partially full

The distribution of boundary shear stress in circular conduits flowing part ially full, with and without a smooth flat bed simulating deposited sedimen ts, has been examined experimentally ranging from 0.375 < F < 1.96 and 6.5 X 10(4) < R < 3.42 X 10(5), using the Preston tube technique The invert lev el of the hat bed and the water depth have been varied to simulate a wide r ange of possible flow conditions that may occur in culverts, sewers, and hy dropower tunnels. The distribution of boundary shear stress around the wett ed perimeter is shown to be highly sensitive to changes in cross-sectional shape. The results have been analyzed in terms of the variation of local/gl obal shear stress versus perimetric distance, and the percentage of the tot al shear force acting on the wall or bed of the conduit. The %SFw. results have been shown to agree well with Knight's empirical formula for prismatic channels. The influence of secondary flows on the distribution of boundary shear stress and the implications of this for sediment transport have also been examined.