Application of a Nonhydrostatic Model to Flow in a Free Surface Fish Passage Facility

Abstract

The free surface flow of two conceptual fish passage designs are investigated numerically by a level-set finite-element method. One design has a right-angled entrance from the reservoir to the fish passage chute, and the other has a curved-shaped entrance. The numerical results are validated with hydraulic experiments through comparison of the free surface location and the pressure distribution in the spillway. It is found that the right-angled design yields a curved free surface and pressure distribution in the vicinity of the entrance due to large strains, whereas the curved-shaped design yields a smooth flow transition with small strains. The negative pressure distributions near the ogee crest for both designs exhibit similar characteristics. Further downstream the free surface is elevated near the wall and is associated with counterrotating vortices. It is concluded that the curved-shaped design is favorable for fish passage because of the feature of a smooth flow transition with small strains.