Experimental investigation of hydraulic jump in Hexagonal Ez Stilling Basin

Hydraulic jump is used as an important energy dissipator phenomenon downstream of hydraulic structures such as spillways, gates, and chutes. The US Bureau of Reclamation (USBR) surveyed the state of knowledge in this field and presented practical guidelines for the design of different types of stilling basins (Peterka 1958). However, it is always preferable to achieve maximum energy loss with a minimum length and cost in the stilling basin. Experimental studies on the effect of gradually diverging stilling basin walls on the hydraulic jump parameters have shown that diverging walls cause a reduction of the sequent depth by up to 30%, a reduction of the length of the hydraulic jump by up to 22%, and an increase in the energy loss compared with the classic hydraulic jump (Kouluseus and Ahmad 1969; Khalifa and McCorquodale 1979; Omid et al. 2007). Hassanpour et al. (2017) studied the characteristics of the hydraulic jump in a gradually expanding rectangular stilling basin. They showed that the sequent depth ratio and relative length of the jump decrease with decreasing divergence ratio. Arabhaabhirama and Abela (1971) studied radial hydraulic jumps in a gradually expanding rectangular channel with divergence angles from 0 to 13◦. The results showed that the divergence of the walls causes reductions in the sequent depth and length of the jump and an increase in energy loss as compared to the hydraulic jump in a straight rectangular channel.Since the hydraulic jump changes the flow from the supercritical to the subcritical, on the other hand, the flow depth is decreased in the expanding and diverging stilling basins in the supercritical and subcritical conditions, respectively. The innovation of this research is the use of divergent-convergent stilling basins to increase the performance of the stilling basins.  The results of the divergent-convergent stilling basin were compared with the classic and divergent basins as well as previous research.