Equivalent Roughness of Submerged Obstacles in Open-Channel Flows

Experimental results for flow in a 16.5% sloping channel over various kinds of submerged artificial large-scale roughness elements are presented. Eight different shapes of obstacles are tested, as follows: (1)standard baffle blocks, (2)cubes, (3)half-cubes, (4)angles, (5)cylinders, (6)vertical rods, (7)hemispheres parallel to the flow, and (8)hemispheres normal to the flow. Based on depth measurements, the effective Manning's coefficient is determined and the respective equivalent sand roughness is evaluated. The results are given in nondimensional terms and compared with previous research. The effects of shape, size, and density of the obstacles on flow resistance are discussed.