Case Study of an Application of a Computational Fluid Dynamics Model to the Forebay of the Dalles Dam, Oregon

Abstract

A proposal for facilitating the downstream migration of juvenile fish at The Dalles Dam, Ore. calls for blocking the upper 12.3 m of turbine intakes by J-shaped steel panels (blocked trashracks). These trashracks are expected to reduce velocity near the powerhouse that is responsible for entraining juveniles into the turbine intake flow. A three-dimensional computational fluid dynamics model was used to investigate the forebay hydraulics for the existing and proposed configurations of the intakes. Velocity data from a 1:40 scale physical model and a field program were utilized for model validation. In general, agreements between computed velocities and data were within the variability of field measurements. The model results confirmed the development of low velocity zones adjacent to the powerhouse. Further, the flow field created by the proposed trashracks could aid juveniles in swimming to the downstream end of the powerhouse where the fish bypass system is located.