A selective literature review of vortex rope in turbine draft tubes and the associated induced pressure pulsations in the conveyance system

A vortex rope (VR) predominately arises in the draft tube (DT) of a reaction turbine and its presence often has profound implications for system operation and stability. This paper overviews 30 years of recent published investigations into the VR and the associated VRinduced pressure pulsation (VRIPP). The role of VR in the surge performance of the system is specifically explored. Emphasis is given to the evolution of the VR and those properties of VRIPP observed in both experiments and mathematical methods. Specific issues discussed include scale effects related to pressure prediction, the effects of cavitation and resonance, the occurrence of anomalous efficiency drops, the evolution of the VR during transient events and VR mitigation.