Assessment of the Performance of a Modified USBR Type II Stilling Basin by a Validated CFD Model

Abstract

The adaptation of existing dams is of paramount importance to face the challenge posed by climate change and new legal frameworks. Thus, it is crucial to optimise the design of stilling basins so that a reduction in the hydraulic jump dimensions is achieved without jeopardising the energy dissipation in the structure. A numerical model was developed to simulate a United States Bureau of Reclamation Type-II basin. The model was validated with a specifically-designed physical model and then was used to simulate and test the performance of the basin after adding a second chute blocks row. The results showed a reduction in the hydraulic jump dimensions in terms of the sequent depths ratio and the roller length, which were respectively 2.5% and 1.4% lower in the modified design. These results would allow an estimated increase of the discharge in the basin close to the 10%. Furthermore, this new design showed a higher efficiency, with a 1.2% increase in this parameter. Consequently, the modifications proposed for the basin design suggest an improved performance of the structure. The issue of the hydraulic jump length estimation is also discussed, introducing and comparing different approaches. These methods follow a structured and systematic procedure and show consistent results for the developed models.

Investigation of a Negative Step Effect on Stilling Basin by Using CFD

“…A reliable design for stilling basins must consider the hydraulic jump developed within the structure [ 18 ]. Thus, surface jumps should be avoided as much as possible.…”

“…The bottom velocity ( y = 2.0 cm) profiles were measured using a flowmeter. The following dimensionless quantities were used for a comparison between the experiments and numerical simulations: where is the jump toe position; is the roller length; is the flow depth at jump toe; is the bottom velocity ( y = 2.0 cm); is the mean flow velocity at the jump toe [ 18 ].…”

“…The simulation results of four turbulence models (standard k- ε , RNG k- ε , realizable k- ε , and large eddy simulation turbulence models) were compared, and the RNG k- ε turbulence model showed the most successful agreement with the experimental results. Macian-Perez et al [ 18 ] investigated the performance of a USBR Type II stilling basin using a CFD numerical model. The sequent depth ratio, the roller and hydraulic jump lengths, and the energy dissipation efficiency were analyzed in their study.…”