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

Abstract

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.