Effect of Cavitation on the Design of River Outlets of High Dams

The present trend of construction of numerous, multipurpose, high dams on the big rivers of India has engaged the attention of engineering scientists towards a couple of new interesting problems in the designing of their structures. The river outlets which regulate the escapage discharge of the reservoir are complicated and important components and their functioning under high head and high velocities render their design very intricate. This problem was first studied for Bhakra Dam. This paper deals with the role of cavitation in the design of river outlet for high dams. Important aspects such as flow pattern, air-demand, radius of curvature of the elbow at the exit etc., have been thoroughly investigated. It was found that an air venting system comprising of a 24” (0.61m) pipe at the elbow and two 24” (0.61m.) pipes in the horse shoe section spreading air over a suitable angle of distribution of 180° alleviate negative pressures and render the design safe for practical adoption.