Effect of the Artificial Bed Roughness's Shape on Hydraulic Jump's Characteristics

Hydraulic jumps are the most important type of rapidly variable flow that occur in from the supercritical state to the subcritical state with the sudden increase of the water free surface in a relatively short path, and usually has a high kinetic energy dissipation. The presence of a barrier against the flow will result in the separation of the inlet jet and more energy depletion resulting in increased shear stress and increased drag force. As a result, the jump length and conjugate depth decreases. These obstacles must be structurally sound because they are directly in front of the jet. If the flow rate exceeds 17m/s, it will cause a cavitation phenomenon (peterka, 1985). Another factor that can reduce the dimensions of a hydraulic jump is the roughness of the floor. Rajaratnam(1968) conducted the first systematic studies of jumping on a rough bed. The results of Rajaratnam were confirmed by Hager(1992), and, with their study of acoarsebed, Ead and Rajaratnam(2002) showed that the jump length on the rough bed is almost three times the conjugate depth (Lj/Y2=3). Shows that the rippling bed has halved the length of the jump to the length of the USBR-I pond. Studies on roughened bed reveal that the use of rough substrates requires more experiments to determine the proper shape of roughness. Hence, in this study, roughnesses in cubic, triangular and cubic and triangular combinations with zigzag arrangement have been investigated on the hydraulic jump specification in the rang of 5.13 to 9.75 froud numbers.