Flow visualisation of the orthogonal blade-vortex interaction using particle image velocimetry

The flow field produced by the orthogonal blade-vortex interaction (BVI) was examined through the application of a particle image velocimetry (PIV) technique, and acquisition of comparative unsteady surface pressure measurements, The velocity vector maps obtained revealed a significant radial flow from the vortex core after severing, in the form of an outward flow from the core when the flow is directed towards the surface (lower), and inward when directed away (upper). With progression of the vortex over the chord of the blade, the interaction led to a decrease in peak vorticity levels on the lower surface, but a steady level was maintained on the upper surface. Assessment of the effect of the interaction on the out-of-plane mass flux was performed through calculation of the divergence, revealing that there is no further variation in the axial flow on either side of the blade after the initial cut.