Numerical and Physical Modelling of the Performance of the Pro-vortex Vanes in Shaft Spillways

The paper focuses on the analysis of hydraulic conditions in the proximity of the intake part of high shaft spillways equipped with pro-vortex vanes and discusses recent enhancements in modelling of the shaft spillways and compares the acquired results of the performance of the spillway after complete removal or rehabilitation of the vanes in context of capacity and overall hydraulic conditions. Increasing requirements on safety of embankment dams during floods with respect to anticipated effect of the climate change scenarios on parameters of design floods demand further assessment of capabilities of outlet structures to meet the updated needs. Such dam safety assessments often conclude in the need of designing additional measures to improve existing structures. Despite different approach to the evaluation of the uncertainties and subsequent risk assessment the goal of improving safety of large dams remains consistent in the effort of all developed countries. Adjustments of the intake part of shaft spillways can present a valid design option for increasing capacity of the complex spillway/tunnel structure if supported by solid analysis of hydraulic conditions inside these structures. As the governing idea of the pro-vortex vanes is to ensure spiral flow inside the shaft and to minimize the pressure fluctuations the paper presents results from physical model of several designs of the pro-vortex vanes which approximated possible adjustment of tower like shaft spillway of existing large dam in Czech Republic and also results from CFD modelling illustrating the importance of combination of both modelling approaches. For the CFD part, different turbulence models are discussed.

Study on Structure Design of Generator of Flood Discharge Tunnel with Level Swirling Flow

Through the design of the Generator of the spillway tunnel, the safe operation efficiency of flood discharge tunnel with the level swirling flow is further improved. This paper takes the horizontal swirl spillway tunnel of Gongboxia Hydropower Station on the Yellow River as an example. First, the project hub facilities of the Gongboxia Hydropower Station are introduced. Moreover, the design of the gradient section and the spinning chamber section in the Generator is also studied. Based on the calculation scheme of structural mechanics, the internal force of the structure under various load combinations such as external water pressure and internal water pressure is calculated. According to Design Codes For Hydraulic Concrete Structure, the structural reinforcement is computed. These provide the basis for the design of the flood discharge tunnel with level swirling flow of large hydropower engineering facilities in Northwest China.

Experimental study on the shape of plunge pool in the Horizontal Swirl Spillway Tunnel

According to the study on the shape of plunge pool in the horizontal swirl spillway tunnel, the design scheme of a plunge pool with better energy dissipation effect is proposed. Based on the hydraulic physical model test, which includes atmospheric pressure and decompression tests, and combined with the different design scheme of a plunge pool, measurement results of fluctuating pressure. Main frequency and sidewall pressure are analysed. The results show that the inlet section of the plunge pool is connected by a gradual variable section which length of gradient segment 6m. The shape of the gradient section is a long round variable gate hole. To improve the side wall pressure, the inlet section is increasing from 6.0m to 14.0m. Finally, the proposed plunge pool has the advantages of simple design and convenient construction, and these studies provide reference and support for the design of hydropower dams in western China.

A Brief Theoretical Analysis on the Ventilation Characteristics of the Multi-Intake-Well Air Supply System in a Spillway Tunnel

It is of great significance to study the ventilation characteristics of air supply systems in spillway tunnels, especially for high dams. In this paper, a brief theoretical approach to evaluate the ventilation characteristics of a multi-intake-well air supply system was established, which was mainly derived from the Bernoulli equation and continuity equation. With this approach, an analysis of the ventilation characteristics of the Jinping-I project spillway tunnel was carried out. A comparison of the theoretical results and prototype data suggested the theoretical approach to be valid and practical. The value of the drag coefficient at the air-water interface should be calibrated before evaluation because the drag coefficient is crucial for the accuracy of theoretical results. In addition, the influences of certain structural factors of the spillway tunnel and air intake well on the ventilation characteristics of multi-intake-well air supply systems are investigated.