the effect of broad-crested sill on the hydraulic jump characteristics in diverging stilling basins

in a control structures, it is often preferred to minimize the gate width while utilizing the canal width in full for a stilling basin. therefore, to reach this, a gradually diverging stilling basin may be used. in this study, the effect of broad-crested sill on the expanding hydraulic jump in a rectangular channel was investigated. a total number of 79 tests were carried out for the range of initial froude number from 3.1 to 10.3. sills with various heights and of different locations, relative to the jump toe, were installed in the basins with divergence angles of 3 and 5 degrees. in all the tests, the main characteristics of hydraulic jump including sequent depth ratio, relative length of jump and longitudinal surface profile were recorded. the results indicate that installing broad-crested sills exert an insignificant effect on the sequent depth ratio but may considerably decrease the length of jump. in addition, observations indicate that the increase in divergence angle of stilling basin will increase the effect of sill in decreasing the jump length.