Author(s): Dan Gessler; Tom Molls; D. Brown; M. Johnson; Christopher Kissick; Stephen Oldemeyer; Stephen Verigin; Mark Fortner
Linked Author(s):
Keywords: Cavitation; Air Concentration; Spillway; Oroville; Measurement
Abstract: Since 1953 (Peterka, 1953) it has been understood that cavitation damage in spillways is suppressed by the presence of sufficient air concentration in the water. Previous research indicates that the required air concentration to prevent cavitation damage ranges from 0.25 to 10 percent (Peterka 1953, Rasmussen 1956, Falvey (Reclamation 1990) EM-42, Wilhelms and Gulliver 2005, Mortensen 2020). The content contained in this paper was obtained from part of an evaluation of cavitation damage potential for the Oroville Dam Flood Control Outlet (FCO) reinforced concrete spillway. Cavitation damage typically occurs at a surface imperfection; at the Oroville FCO the largest imperfections are at construction joints. The aerator team used a purpose-built water tunnel to test full scale construction joints at prototype velocities to determine the flow at which cavitation damage occurs. Using multiple concrete test articles, an optical phase detection probe was used to measure the required air concentration to prevent cavitation in the Apparatus. In addition, the team experimented with three other (structural) cavitation damage countermeasures: two concrete coating alternatives and one modification to the construction joint geometry. Test results showed that a near surface air concentration of less than 1 percent is sufficient to prevent cavitation damage. Accounting for measurement uncertainty, a 1 percent near surface air concentration is recommended to protect against cavitation damage. Testing also showed that all three joint modifications could supress cavitation damage. This paper presents the development of the Apparatus and describes the testing approach and the study results. These results extend to spillways beyond the Oroville FCO spillway.
DOI: https://doi.org/10.3929/ethz-b-000675921
Year: 2024