Effect of roughness on characteristics of bed B-jump in stilling basin with abrupt drop

Hydraulic jump stilling basins are used as an energy dissipater structures downstream of gates, spillways and weirs. In the present study, the effect of roughened bed on flow characteristics of hydraulic jump at abrupt drop has been experimentally investigated. Total of 42 tests were conducted in a flume of 70 cm in width and 15 m long. Experiments were performed for wide range of Froude numbers ranging from 3 to 5.68. The relative sequent depths and the length of hydraulic jump were plotted against the Froude number for both smooth and roughened bed jumps. The results showed that both sequent depth and hydraulic jump length decreased when the bed was roughened. The maximum reduction was found to be in the order of 14 and 33%, respectively. These results showed that roughened bed at abrupt drop could decrease the cost of stilling basin.