Blade-vortex interaction experiments - Velocity and vorticity fields

The blade-vortex interaction problem is studied experimentally with laser-Doppler velocimetry. Vortices are generated by pitching a NACA 0012 airfoil about its quarter chord and a target airfoil is mounted two chord lengths downstream of the vortex generator. LDV measurements are obtained in the neighborhood of the target airfoil's leading edge and ensemble-averaged velocity vector fields and vorticity contours are constructed. Vorticity fields are also constructed from velocity time records by assuming that, over short distances, the vorticity propagates with the local velocity. This assumption allows the blade-vortex interaction to be simulated from very few measurements.