Investigation of Hydraulic Jump Characteristics at Roughened Bed of Sudden Expansion Stilling Basin

Stilling basins of sudden expansion are one of the energy dissipater structures which can dissipate most of the kinetin energy of the flow through hydraulic jump. In this structure the sequent depth ratio is less and the jump length is more than in classical jump. Since the roughening on the stilling bed can reduce both sequent depth ratio and jump length and its effect have not been investigated before, this study was conducted. In this study many tests are conducted in a relatively large flume size of 80 centimeter wide and 12 meter length. The sudden expansion ratio was 0.33 and tests were conducted for Froude numbers in the range of 2-10. The final results of this study show that for roughened bed sudden expansion stilling basin, the sequent depth ratio is 53 percent and the jump length was found to be 25 lower than in classical jump.