Abstract
Experimental results of characteristics of flow resistance and boundary shear stress distribution along the wetted perimeter of rectangular cross-sectional channels are reported in order to discuss sidewall roughness effects on them. In the experiments, square cross-sectional acrylic bars are employed as artificial strip roughness elements. Three types of arrangement of roughness elements are examined, that is, on the channel bed, the side wall and both of them. Varying vertical slope and discharge, flow resistances are measured. In some selected runs, cross-sectional velocity distributions are measured and shear stresses on the boundary are determined by methods based on the logarithmic velocity law because the velocity profiles fit the law near the boundary. It has been found that effects of roughness elements on the sidewalls are restricted near them affecting slightly total flow resistance even in case with steep slopes and that shear distributions have very high non-uniformity suggesting influences of secondary flows.
