A new type of cavitation triggered by boundary-layer turbulence-production has been identified from the turbines of the Three Gorges Power Station. Our previous studies point out that the addition of the ‘guide-plate’ is responsible for the increase of the turbulence level (in particular the low-frequency mode) in the free-stream which in turn promotes the boundary-layer transition through receptivity mechanism. A new vortex structure identified from our numerical studies is revealed in this paper. It explains well how the free-stream turbulence is influenced by this new vortex structure which is created by the addition of this ‘guide-plate’. These results support one of the claims in the hypothesis proposed in our previous studies. The other claims in the hypothesis about the triggering mechanism of this type of cavitation in the boundary-layer are being verified through our on-going (numerical and experimental) studies. The numerical studies reported here are performed by using CFD simulations of the entire flow passage of the prototype turbine.

Issue Section:
Flows in Complex Systems
Keywords:
boundary layer turbulence, cavitation, computational fluid dynamics, flow simulation, fluctuations, hydraulic turbines, power stations, vortices
Topics:
Flow (Dynamics), Fluctuations (Physics), Guide vanes, Pressure, Turbines, Vortices, Cavitation, Turbulence, Engineering prototypes

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