Cavitation

Learn more about the dangers of cavitation at DamFailures.org

"Cavitation damage is initiated by spillway flows over a defect along the flow surface. The defect creates localized negative pressures within the flow which create vapor bubbles. Individual vapor bubbles converge and form larger vapor cavities. When the vapor cavities impact the flow surface they implode and generate large forces which damage the flow surface. Cavitation generally requires long flow durations (weeks or months) to produce significant damage. The potential for cavitation damage to initiate can be predicted with the cavitation index, which is a function of the flow velocity, the pressure along the flow surface and the vapor pressure of water. A case history of extensive damage to the spillway lining and foundation due to cavitation is the Glen Canyon Dam Spillway (see Best Practices: Reclamation and USACE 2019). Ball milling is a mechanism in which cobble and gravel sized material is introduced into a hydraulic jump stilling basin and remains in place. The trapped material is caught in a cyclical flow pattern that abrades the concrete surface. Significant concrete damage can occur, but it takes very long durations." ^[1]