Author(s): V. V. Bhosekar; V. Jothiprakash; P. B. Deolalikar
Linked Author(s): V. Jothiprakash
Keywords: Orifice spillway; Negative pressures; Cavitation damage; Aerator design
Abstract: Orifice spillways are low level large openings located 30-40 m below the full reservoir water level as near the river bed as possible in the dam body for dual purpose of flood disposal as well as flushing of sediment from the reservoir. High velocities of the order of 25-30 m/s over the spillway crest makes it susceptible to cavitaton damage. Aeration is one of the easiest and cost effective methods to mitigate the cavitation damage by introducing aerator near the spillway surface. Much work has been reported on aerators for the overflow spillways. However, design of aerators for orifice spillways is still a grey area. Hydraulic model studies were conducted on a 1:25 scale model at Central Water and Power Research Station (CWPRS), Pune, India for evolving design of aerator for 60 m deep seated orifice spillway. Pressure profiles, water profiles, cavity sub pressures and air flow entrained by the lower nappe of the 1.5m offset aerator were measured for the entire range of water levels and discharges for full and partial gate operations. Data in respect of jet length, Cavity sub pressures and air concentration with variation in Froude number is presented which will be useful for designing the aerator for flat slope orifice spillways.
Year: 2010