Research Note «Laboratory Assessment of Hydraulic Jump Properties in a Riprapped Stilling Basin

Hydraulic jump dissipates destructive energy downstream of spillways and chutes. Stilling basin materials have considerable impacts on hydraulic jump properties. As the roughness of stilling basins increases, the length and conjugate depth of jump reduces, and this will affect the dimensions of stilling basin and as a result the cost of structure. One of the methods used for this purpose is to use riprap on the bed of basin that will in turn create a continuous roughness. In the present study, the hydraulic jump characteristics were experimentally investigated over two sizes of ripraps used to furnish the stilling basin bed in a rectangular flume that has the dimensions of 0.4 m wide, 0.4 m deep and 12 m long. The results showed that the length, depth and rolling length of hydraulic jump of riprapped basins were reduced by 35, 50 and 49 percent respectively when compared to those with smooth bed. In addition, the results showed that the variations in bed riprap sizes from 4.45 to 5.75 millimeters reduced the length of jump by 13.5 percent compared to smooth basin. However, there is no significant impact of riprap size on conjugate depth.