Vortices forming behind mechanical components inside a turbine is the cause of many unwanted phenomena; “singing stay vanes”, high frequency noise from guide vanes that can come in resonance with other components in the system, vortex shedding on the trailing edge of runner vane s might come in resonance with the blade itself and result in fatigue and fracture.

The current methods for dealing with such phenomena are sensitive to manufacturing error, and occasionally there are still units that experience problems. 

Learn from natures own design

Task 2.6 will work on using design found in nature to avoid the forming vortices having too high frequency and amplitudes.

More specifically, the effect of having an uneven trailing edge geometry rather than the even edge currently used in turbines.

The inspiration comes from owls, which has a very silent flight, partially enabled by an uneven trailing edge on the wing.

Another assumed problem related to an even trailing edge is the problem of pressure oscillations occurring when the leading edge of the runner vane passes near the trailing edge of the guide vane. When the trailing edge (and leading edge) are even, the pressure build-up will occur very evenly and more or less simultaneously over the entire geometry. This will give a pressure wave with high amplitude propagating through the turbine.

The hypothesis is that an uneven trailing edge will give a pressure build-up that is occurring differently on the geometry, and the pressure waves will mitigate each other and the propagating pressure wave will not have as high amplitude as for an even trailing edge geometry.