On the Effects of Water Discharge Through Radial Gates at the Caruachi Dam

Abstract

This paper presents numerical simulation of the water flow through the radial gates of the 2,280 MW Caruchi Dam, in southern Venezuela, and its relation to the vibration of the dam’s spillways and adjacent Control Building. The study is conducted as a contribution in determining the source of vibration of the fore mentioned structures in the case of gates opening above the normal values of up to 5 m, which occur when a larger water discharge is required in order to maintain an adequate level of the reservoir during the rainy season. The aim of the study was to find the pressure distribution and velocity profiles of the discharge flow through one of the dam’s radial gates and determine critical (reduced) velocities that may result in flow-induced vibration of the gates, as they were deemed to be the source of vibration of the whole set of structures in the first place. For this purpose, a commercially available FEM code was used. Three-dimensional CFD models were developed to simulate behavior of the flow when being released to the spillways, for opening values of 2, 5, 10 and 14 m, including the effect of the spillways’ deflectors. Modal analyses of the gate were performed, to take into account natural vibration frequencies in the determination of its critical velocities. After comparison of the gate’s critical velocities and velocity values from the CFD simulations, it is fair to say that the discharge flow does not directly induce vibration on the gates but rather on the spillways’ structure. This conclusion disregards flow through the gates as triggering the vibration phenomena which gave origin to this project, and puts the emphasis now on studying water flow effects on vibration in the spillway which, if not corrected on time, may ultimately lead to its catastrophic failure.