Numerical models in The Dalles tailrace are being used to support efforts to reduce fish mortality associated with fish passaging of the hydroelectric project. At The Dalles, several locations have been proposed for a high flow outfall that would move fish around the dam rather than through the turbines or over the spillway.

Figure 1 - Bathymetry of The Dalles

The numerical model was a steady-state, rigid lid model, hence the computational mesh needed to have the option of removing or adjusting the top layers for flow scenarios with higher or lower tailwater elevations. This meshing approach increases the suite of flow scenarios for which the mesh can be used without the need to generate and validate a new computational mesh. Flow results (Figure 2) are validated to field-measured data, reduced-scale physical model data, and results from another CFD flow solver. In the future, free-surface simulation results from the high flow outfalls will be used to provide inflow conditions to the STAR-CD model. These results will be used to support high flow outfall location decisions.

Gridgen Version 14’s ability to project to STLs made it possible for us to create complex 3D hybrid meshes of the river and engineered structures. The use of the STLs in Gridgen Version 14 also allowed us to use a common set of geometric and bathymetric base data for multiple CFD solvers with different geometry requirements.

Figure 2 - Flow simulation of The Dalles