Vibration of Water-Turbine Draft Tubes

The vibration in the draft tube of a water turbine is most severe when the turbine is running on part load. This is caused principally by the vortex core of whirling water in the draft tube. The theoretical and experimental investigations of the frequency and force of periodic vibration caused by the vortex core are described, and there is clarification of the draft-tube surge caused by vibration due to the vortex core.