PNNL

Abstract

Based upon acoustic tracking and fish tagging data, The Dalles Project constructed and operated by the U. S. Army Corps of Engineers has been shown to have the highest mortality rates for juvenile salmonids on the Lower Columbia River. In efforts to assist the hydraulic and biological communities in managing this hydroelectric project, a three-dimensional computational fluid dynamics (CFD) model was applied to the spillway, stilling basin, and tailrace zones downstream of the dam. To simulate the highly transient and turbulent flow conditions in this region, a free-surface computational fluid dynamics (CFD) numerical model has been applied. This model is based upon the volume-of-fluids (VOF) method, and is capable of simulating sudden discontinuities in the free surface, including wave breakup. The model solves the non-hydrostatic Reynolds-averaged Navier-Stokes (RANS) equations over variable-sized hexahedral cells. To verify the ability of the numerical model to simulate flows downstream of the spillway, the model was verified against data from three different physical models of The Dalles tailrace at scales of 1:36, 1:40, and 1:80. Results from these physical models allow for validation of the numerical model at various scales of motion from the small scale highly dynamic variations near the baffle blocks (1:36 and 1:40 scale) to the larger scale general circulation patterns that encompass the tailrace (1:80 scale).