Hydraulic Jump Characteristics at an Abrupt Drop under Influence of Artificial Roughness

Abrupt drop is a sudden lowering of the channel bed which is done for reduction of hydraulic jump length and to ensure that the jump will not be shifted outside the basin for various flow conditions. This type of basin is used in irrigation and drainage networks as an effective measure for dissipation of kinetic energy. Since the roughened bed of basin also can reduce the stilling basin length، the use of both abrupt drop on bed and roughness can reduce the jump length even more. Therefore it is the main goal of this study to conduct experimental tests on a large scale model to see how the roughness can affect on jump characteristics. To reach such goal tests conducted on a flume of 80cm wide، 15m long and 60cm high. The flow discharge ranged from 56lit/sec to 230l/sec providing Froude number in the range of 2. 5 to 9. 0. The results of this study show that the jump length reduces to about 36% of classical jump length. In comparison with jump in smooth bed of abrupt drop، the amount of reduction reaches as high as 53%. The observation al results show that the location in which the jump starts، is almost constant in all tests and the sequent depth ratios have almost the same value as in classical jump.