Seite - 723 - in Book of Full Papers - Symposium Hydro Engineering

1. INTRODUCTION As water utilization and demand for hydropower has expanded, the development of high dams containing large reservoirs have increased globally. Due to the high water head of a high dam with a large reservoir, vibrations caused by fluctuating flow loads generated by water energy can be transmitted underground to the surrounding area via the dam’s foundations. Due to the "magnifying effect", vibrations can be enhanced when special ground conditions are present, an effect that will increase their impact on the surrounding environment [1]. Vibrations caused by high dam flood discharge, and their effect on the structural safety of surrounding buildings and the environment, as well as on the physical and mental health of the local population, have been recorded [2- 4]. Therefore, research on this phenomenon is urgently needed. Vibrations associated to high dam flood discharge have a close relationship with the hydrodynamic condition and dynamic characteristics of the discharge structures. As the mechanism of fluid-structure coupling vibration is fairly complex, the effective research method to solve the vibration problems induced by high dam flood discharge is to establish a fluid-structure interaction physical model through complete hydroelasticity simulation, and to undertake flood induced vibration tests [5-8]. In this study, by using a bottom-flow energy dissipation hydropower station in China as a case study, approaches to improve the traditional hydroelastic model for ground vibrations induced by flood discharge are proposed. The main factors influencing ground vibration intensity was studied by establishing a correlation system between the dam model and the actual ground in order to provide a theoretical basis to analyze vibrations and damping techniques for high dams. 2. EXPERIMENTAL PRINCIPLES The hydroelastic experiment simulation of flow-induced vibrations simulates the fluid-structure interaction vibration system combined with "structure - water - foundation - dynamic load". The "dynamic load" input system similarity and the dynamic response similarity of structural systems are simultaneously required for the simulation, which means that the similarity of the hydraulic condition and the structural dynamic condition are simultaneously required [9]. The hydraulic similarity is the similarity of the "dynamic load" input system, and its essence is the similar law of fluctuating pressure in the hydraulic model designed by similar law of gravity. By comparing a series of scale model tests and prototype observations, it was found that the side fluctuating pressure, caused by flow separation or diffusion induced by the dramatic change of integral boundary and flow conditions, was mainly controlled by large-scale and low-frequency vortex motions. The large-scale vortex motion was successfully simulated in the model with a large enough Reynold’s number, and fluctuating pressure can be extended 723