Hydraulic Model Studies of Chute Offsets,Air Slots,and Deflectors for High-Velocity Jets,

摘要

High-velocity jets discharging through slide gates into lined tunnels and chutes at outlet works installations have caused serious cavitation problems at several structures. To prevent cavitation erosion,air must be introduced along the underside and sides of a jet before the jet comes in contact with downstream concrete surfaces. Model studies of chute offsets,air slots,and deflectors were conducted to determine methods to aerate the jet and provide recommendations for altering two existing structures and designing new structures. A single test facility was used to model existing structures at Palisades and Navajo Dams and proposed structures at Pueblo,Crystal,and Teton Dams. Wall air vern slots combined with a floor deflector were developed for use immediately downstream from the gate frames in the two existing structures. Wall and floor air vent offsets away from the flow at the end of the frame were developed for new structures. These investigations,supplemented by general research,formed the basis for guidelines developed for design of future air-entraining devices to protect flow surfaces from cavitation erosion.