Author(s): K. Warren Frizell; Nathan C. Cox
Linked Author(s): Kenneth Warren Frizell
Keywords: No Keywords
Abstract: Studies were completed at Reclamation's hydraulic laboratory to evaluate the cavitation potential for baffle blocks within a modified type III stilling basin at the terminus of a novel stepped spillway. The spillway features a smooth chute section and a stepped portion, leading to the stilling basin and the largest design unit discharges for a stepped chute to date. Several combinations of block shapes and floor ramps were testing in Reclamation's Low-Ambient Pressure Chamber (LAPC). Reduced atmospheric pressure allows for the evaluation of the cavitation index for a particular block shape, which can then be applied to the design. The goal was to produce block designs that will supercavitate at the design discharge, causing the dissipation of the vapor cavity to be well downstream from the block structure. Cavitation detection and intensity measurements were done using a mass-loaded acoustic emission transducer mounted on the test section. Visual observations were possible using a high-speed video camera and frame rates up to 2000 Hz. The design of a supercavitating block was accomplished using the LAPC and a partial sectional model. A tapered block and floor ramp combination should eliminate damage to the blocks and the floor in close proximity. There is some uncertainty about the possible damage that could occur at the closure of the ventilated cavity downstream from the row of blocks, however if damage does occur at this location, the magnitude is expected to be less, and it would be limited to the floor and more easily repaired.
Year: 2009