Experimental Optimization of Gate-Opening Modes to Minimize Near-Field Vibrations in Hydropower Stations

Abstract

Multi-Horizontal-Submerged Jets are successfully applied to dissipate energy within a large-scale hydropower station. However, notable near-field vibrations are generated when releasing high discharges through the gates, which is generally typical in a flooding case scenario. Under these conditions, the magnitude of the vibrations varies when applying different gate-opening modes. To investigate and find optimized gate-opening modes to reduce the near-field vibration, multiple combinations were tested by varying gate-opening modes and hydraulic conditions. For each of the tests conducted, fluctuating pressures acting on side-walls and bottoms of a stilling basin were measured. The collected datasets were used to determine the maximum and minimum fluctuating pressure values associated with the correspondent gate-opening mode and a detailed comparison between each of the gate-opening modes was completed. The paper presents the quantitative analysis of the discharge ratio’s effect on fluctuating pressures. It also investigates the influence of different gate-opening modes by including side to middle spillways and upper to lower spillways configurations. The flow pattern evolutions triggered by each different gate-opening mode are discussed and optimal configurations that minimize near-field vibrations at high discharges are recommended to support both the design of new systems and assessment of the performance of existing ones.

An Evaluation and Reduction Approach for the Ground Vibration Induced by High Dam Flood Discharge

“…Therefore, the vibrations of SBP and the surrounding ground can be reduced by optimizing these influencing factors. The time and frequency characteristics of hydrodynamic loads have been optimized by researchers [9,25] by improving the flow pattern in the stilling basin, which attenuates the vibrations to a certain extent. However, ground vibration is still perceptible, especially under working conditions with large volumes of flood discharge.…”

“…Another reference [14] proposed a method to calculate area fluctuating pressure from point fluctuating pressures, and further obtained the excitation-response correlation for the prediction of ground vibration velocity. Aiming at minimizing ground vibration and satisfying the flood discharge requirement in the meantime, researchers presented an optimal flood discharge scheme based on numerical simulation [15], hydraulic model tests [25] and hydro-elastic model tests [9]. It is noted that although the above studies focused on different aspects, the evaluation and reduction methods based on the influence of structural characteristics on ground vibration are still insufficient.…”

Needs and Opportunities for Testing of Hydropower Technology Innovations

“…Velocities and water quality are typically monitored in stilling basins to evaluate the dissipation efficacy and the air entrainment at the bottom of spillways. Pressure fluctuations on the surface of spillways, gates, and other structures where fast flows occur are measured to monitor vibrations and the potential formation of cavitation and erosion (Peng et al 2018). Pressure fluctuations and propagation are also measured frequently in penstocks because they are prone to failure caused by pressure shockwaves (Cai et al 2017).…”

Numerical investigation on characteristics of vortex dissipation in multi-horizontal submerged jets stilling basin

“…The investigation on stilling basin with multi-horizontal submerged jets have been conducted by numerous scholars [ 2 – 6 ]. Zhang et al [ 7 ] established the relationship between the energy dissipation rate and the ratio of jet outlet width to the width of the stilling basin, and the water depth in the multi-horizontal submerged jets stilling basin.…”