Abstract: The Karman vortex shedding is closely related to the shape of the trailing edge of vane. In order to study the effects of the dovetail trailing edge of stay vanes on vortex shedding, the vorticity field of the stay vane is analyzed in this article to find out the general rules of vortex motion by using vortex dynamics. Numerical simulation of Francis turbine’s tandem cascade is conducted with the vorticity field of the original and dovetail stay vanes and the pressure pulsations are then compared. The simulation results show that in comparison to the original vane, the vorticity value and pressure pulsation of the dovetail stay vane wake are relatively less. The split angle extends the vortex motion distance, limits the growth space of new vortexes and lowers the energy of vortexes. The dovetail trailing edge of the stay vane has an inhibitory effect on vortex shedding, which weakens the damage capability of vortexes.

Key words: hydraulic turbine, stay vane, Karman vortex, vortex dynamics, dovetail modification