Aeration in Bottom Outlet Conduits of Dams for Prevention of Cavitation

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Aeration in Bottom Outlet Conduits of Dams for Prevention of Cavitation

Original Article, B35
Kolachian R, Abbaspour A, Salmasi F.
Journal. Civil Eng. Urban. 2(5): 196-201. 2012.

ABSTRACT:The more necessity of human communities to water resources demand leads to establishing and development of high dams and hydraulic structures with high capacities. With increasing in dam height, the water velocity in bottom outlet conduits increases. In the case of decreasing of local pressure due to sudden change in flow area or the passage slope the possibility of cavitation occurrence through the structure increases. Experiences showed that the flow aeration can decrease the risk of cavitation damages effectively. The investigations of flow characteristics by numerical methods along with physical hydraulic models can be effective in choosing the best choice for aeration and also decrease extra cost and time of physical modelling. In this research, first, the cavitation occurrence in bottom outlet of Sefidroud dam was evaluated in different gate openings by Fluent software in 3D mode and then after the comparison results of numerical and physical model, a method for aeration of this structure consist of aerator ramps on floor and side walls of conduit is suggested and investigated by numerical model. For this purpose the VOF model was used for flow simulation in tunnel and the water surface profile, mean velocity, static pressure and cavitation index were investigated before and after aeration. The results showed the relative capability of numerical models in flow simulation in bottom outlet conduit of dam and improving the flow conditions after aeration. 
Keywords:Aeration, Bottom outlet conduit, Cavitation, Fluent

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