Vortex drop shaft structures: State-of-the-art and future trends

Vortex drop shaft structures have played a critical role in hydraulic engineering; from one of their first applications in hydroelectric energy dissipation in the 1940s, to numerous contemporary installations throughout modern day urban drainage infrastructure. They are known to convey flows up to 1400 m3 s through drop heights of 190 m and due to their small footprint, stable flow mechanics and enhanced energy dissipation, they are often considered to be the most successful form of hydraulic drop structure. There are several design questions on various aspects of vortex drop shaft structures that have not yet been addressed in the laboratory environment or at full-scale and moreover will require full appreciation by engineering practitioners in future years. This article summarizes over 75 years of research and development of vortex drop shafts including types of structure, applications, laboratory modelling techniques, physical modelling studies and recent advancements in multiphase numerical modelling. The article discusses the hydraulics of various types of vortex drop shaft structures such as the key design differences between subcritical and supercritical intakes, energy dissipation, and aeration and presents the insights gained from successful case study commercial projects. The outcomes of seminal research studies and projects are discussed in detail and areas that are deemed to require further research and development are highlighted.