Experimental study for the characteristics of flow in semicircular channels with free overfall

In this study, the effects of flow characteristics and size of sediments at different channel slopes on the flow over the edge of the free fall in semicircular channels has been studied. For this purpose, four models of free over fall semicircular channels were constructed and tested in the laboratory channel. These models have a length of (2) m. The longitudinal slope of each model has been changed four times as follows. (S = 0, 1/200, 2/200 and 3/200) or (S = 0, 0.005, 0.01 and 0.015). The roughness was determined by three gradients of sand grains (2 mm, 4.75 mm and 6.33 mm) for each model slope. The laboratory program was divided into sixteen groups, including four groups for smooth surface and twelve groups for coarse surface. Ten different discharges were applied. The final depth relationship with the discharge had been calculated each time for the purpose of studying the hydraulic performance of all tested models. It was found that the Froude number of the experiment varies from (0.13) to (2.22). The discharge values vary in the range of (2 m3/hr) and (11 m3/hr). The discharge equation of the semicircular channel had been estimated by using statistical analysis program (SPSS 25).