Investigation of the Effect of Roughness Wave Length on the Hydraulic Jump Characteristics of Roughened bed

Document Type : Research Article


Associate Professor of Water Engineering Department, Shahrekord University, Shahrekord, Iran


In this study, variation of hydraulic jump characteristics including jump length and secondary depth
and the variation of the effective length of roughness in relation to the wave length were studied. For
this purpose, the characteristics of hydraulic jump under four different wave lengths and four different
Froude numbers were experimentally determined. Totally, 84 tests have been carried out in the range
of Froude numbers from 5.84 to10.13 in a flume with length of 12 m , width of 40 cm, and height of
40 cm. The results showed that the characteristics of hydraulic jump such as length of jump and
secondary depth declines as the length of roughness increases. It was also found that, the effective
roughness length on the secondary depth increases as the wave length increases, but the effect of
roughness length on the length of jump is reverse. Regarding the derived relationships, the optimum
dimensionless wave length was obtained to be 4.5.