2023 – Improving Dissipator Basin Designs by Using New Knowledge of the Fundamental Flow Processes in Hydraulic Jumps

Laura Montano, Stefan Felder

Hydraulic jumps are a complex hydraulic phenomenon typically used for dissipating the energy downstream of spillways. Most common design practices are focused on upstream and downstream flow conditions and the dissipative processes inside the hydraulic jump are considered as a “black box”. The dissipation efficiency of hydraulic jumps is affected by the inflow conditions and available research is limited. To provide new insights into the effect of inflow conditions on stilling basin design, this study investigated the hydraulic jump performance for different boundary layer development in the supercritical approaching flows on horizontal beds as well as in mildly sloped channels, which resembled Type B and D jumps based on their location on the slope. Hydraulic jumps with fully developed inflows showed larger conjugate depth ratios, shorter jump rollers, larger aeration, larger streamwise flow velocities and larger jump toe oscillations, while the energy dissipation efficiency remained unchanged. These results suggest that hydraulic jumps with fully developed inflow conditions may require shorter stilling basin lengths but will be more unstable compared to hydraulic jumps with partially developed inflows. For the hydraulic jumps on the slope, the inflow conditions also affected the dissipation performance and stability. Type D jumps dissipated less energy compared to a classical hydraulic jump, but the jump toe was more stable. Type B jumps and classical hydraulic jumps compared well in terms of energy dissipation, while Type B jumps were more stable, suggesting that Type B jumps on a mild slope could be an effective way to improve stilling basin design. Overall, this research shows that there are opportunities to improve stilling basin designs, but systematic research with state-of-the-art instrumentation that incorporates flow aeration, energy dissipation processes and hydraulic jump stability is required.