Hydraulic Performance of the Control Butterfly Valves of the Bottom Outlet of Kassa Chai Dam

Abstract

A B S T R A C TThe bottom outlet of Kassa Chai Dam, Kirkuk, Iraq was designed and constructed to control the storage outflow by using two 1.4m diameter butterfly valves at its end two branches. During the dam commissioning, a series of operation tests were conducted on the bottom outlet under different openings of its valves. Intense noise and vibration were noticed and reported at these valves. To specify the causes of these intense noise and vibration and to propose solutions to eliminate them, the velocity profiles and pressure variations along the bottom outlet of Kassa Chai Dam and at its valves were investigated. A fullscale 3D mathematical model for the bottom outlet was analyzed by using the commercial CFD code Fluent. CFD Fluent based on solving Navier-Stock equations by finite volume method. The standard k-ε turbulence model was selected to deal with turbulence. Simulations were carried out under different operation conditions, including different water levels of the dam reservoir and different angles of the valves opening as well. Outline from study showed that negative pressures developed at the downstream side of the valve especially at small angles of valve openings. To overcome the problem of negative pressure, a suitable solution is suggested to improve the outlet performance by installing a cone valve at the downstream end of the bottom outlet. Results of investigation when using the cone valve showed that no negative pressure developed at the end of the bottom outlet.