Hydraulic Model Studies of Navajo Dam Auxiliary Outlet Works and Hollow-Jet Valve Bypass-Modifications to Reduce Dissolved Gas Supersaturation,

摘要

It has been observed that operation of the auxiliary outlet works and the 762-mm (30-inch) hollow-jet valve bypass at Navajo Dam result in high levels of dissolved gas supersaturation in released waters. These high dissolved gas levels,which are caused by the deep penetration of the flow into the spillway stilling basin pool,have had adverse effects on the fishery. Structural modifications were considered which included a flattening of the trajectory of the jet from the 762-mm (30-inch) bypass and the addition of a deflector or flip lip to the auxiliary outlet works. A 1:48scale hydraulic model was used to refine and evaluate these modifications. Depth of jet penetration,degree of energy dissipation,strength of back eddies returning into the stilling basin,potential for cavitation development below the flip lip,and simplicity of design were factors considered in the evaluation.