Hydraulic Model Test of the Bottom Outlet of Sivand Dam
This paper presents the results of hydraulic test of bottom outlet of the Sivand Dam. The aims of the hydraulic model test are, gate discharge characteristics and gate loading. Results for different gate openings are also compared with calculated values obtained by a finite element method. Key-Words: Hydraulic model test, Dam, Finite element method, Gate, Gate Discharge
Investigation on cavitation occurrence potential in Seymareh dam’s bottom outlet
ABSTRACT Cavitation phenomenon is one of the common problems of bottom outlets which convey high-speed flows. In the present study, the possibility of cavitation occurrence is numerically investigated. A numerical model is developed for the flow passing through bottom outlet using FLOW 3D software and K-ε (RNG) turbulent model. The model is operated for reservoir normal and maximum water heads also for various service gate openings. For normal head and different service gate openings, the research results show that cavitation indices are lower than the critical amount (0.2) on the conduit bed for 10%, 20%, 30%, 40%, 50%, 70%, and 80% service gate openings. Also, the side walls of conduit encounter with cavitation phenomenon immediately downstream of service gate for all gate openings. It is observed that the conduit top wall is free of cavitation damage hazard where the minimum cavitation index is equal to 0.46. At maximum reservoir head, the cavitation is not occurred inside the emergency gate slot and on its walls.
Water Waves and Structural Loads Caused by a Periodic Change of Discharge from a Sluice-Gate
Characteristics of water waves and structural loads induced by a forced and periodical change of discharge from a sluice-gate were theoretically analyzed, as the first approach for making clear dynamical characteristics of Tainter-gates which are being used with increased frequencies in order to control the water level of dam. It was concluded as follows: A basic parameter characterizing water waves and structural loads is the modified Froude number F0=√(d0/g)·ω(d0: the depth of the gate-opening, g: the gravitational acceleration, ω: the frequency of an oscillatory discharge). Characteristics of water waves are very analogous to the resonance characteristics of the forced oscillatory system consisting of a mass, a spring and a viscous damper. When F0 is equal to about 0.8, wave motions fall into a resonance state. Characteristics of fluid-induced structural loads suggest a possibility that Tainter-gates fall into a self-excited oscillatory state. These theoretically obtained results were proved by experiments.