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 optimize the design of stilling basins to reduce the hydraulic jump dimensions without jeopardizing the energy dissipation in the structure. A numerical model was developed to simulate a US 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 row of chute blocks. The results showed a reduction in the hydraulic jump dimensions in terms of the sequent depth 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 10%. Furthermore, this new design had 1.2% higher efficiency. Consequently, the modifications proposed for the basin design suggest improved performance of the structure. The issue of the hydraulic jump length estimation also was discussed, and different approaches were introduced and compared. These methods follow a structured and systematic procedure and gave consistent results for the developed models.