LARHYSS Journal
Volume 18, Numéro 4, Pages 141-162
2021-12-05
Investigation Of Vacuum And Cavitation Of Shaft Spillway With A Polygonal Cross Section
Authors : Abderrezak Brakeni . Alim Petrovic Guryev . Buchra Haek .
Abstract
In this research paper, our study focused on the importance and reliability of the shaft spillway flow in order to avoid the presence of vacuum and the possibility of erosion by cavitation at high flow rates. The proposed characteristics of the intake funnel consist on 12-section polygonal configuration, on which a total of 124 piezometer gauges in the scale model (including the elbow) was placed to determine the pressure distribution. The physical model in the form of a dodecagon was tested on laboratory flume at the hydroelectric power stations of the State University of Environmental Engineering in Moscow (Russia). This flume having a zero bottom slope, a width of 100 cm and a length of 950 cm is connected to a feed tank whose dimensions are 1.64 m x 2.0m.The results showed that the realization of the crest of the intake funnel in the form of a polygonal cylindrical surface reduces the maximum vacuum by two times compared to the vacuum on the crest of rectilinear weir dams, not exceeding a value of 2 m of water column which is not dangerous for the appearance of the cavitation erosion of the water receiving funnel. It also allows shaft surfaces to be formed with a one-dimensional curvature during construction without the formation of bending edges, thus facilitating flow through the shaft and the discharge gallery.
Keywords
Shaft spillways ; polygonal section ; receiving funnel ; vacuum ; erosion by cavitation.
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