Theoretical and Experimental Study of Gradually Diverging Hydraulic Jump in Trapezoidal Sections

To reduce the construction costs of stilling basins of hydraulic jump type is sometimes, novel geometries are sometimes used to adopt the basin to the upstream and downstream sections without any transition structures. Otherwise, any changes in the geometry of the basin would cause changes in the conditions and characteristics of the hydraulic jump. In this study, the effects of variation in both the side slopes and the diverging angle of a gradually expanding stilling basin with trapezoidal section on the jump condition were experimentally investigated. The experimental tests were conducted in a specially designed model for a wide range of side slopes and longitudinal divergences of the basin walls. The important parameters of the jump, such as the length, sequent depth and the rate of energy loss were computed and compared to those in the normal jumps. Tests were conducted for three different side slopes (0.5:1, 1:1, 1.5:1) and four diverging angle (3o , 5 o, 7o, 9o) with the straight jump in the rectangular section and in the wide scope of decsent numbers (from 3 to 9). The results indicate that any decrease in the side wall slopes for a particular angle of divergence would cause a reduction in the sequent depth and an increase in the jump length and energy loss compared to the rectangular section on the same angle of divergence. It is also found that the longitudinal divergence of the side walls for a particular side slope will increase the stability of the jump within the stilling basin. It will also cause a reduction in the sequent depth and the jump length as well as an increase in energy loss of the jump, when compared to the straight jumps in either rectangular or trapezoidal sections.