PERPENDICULAR BLADE-VORTEX INTERACTION

The interaction between a streamwise vortex and a spanwise blade was s tudied in incompressible flow for blade-vortex separations between +/- 1/8 chord, Three-component velocity and turbulence measurements were m ade from 4 chord lengths upstream to 15 chord lengths downstream of th e blade using miniature four-sensor hot-wire probes. The interaction o f the vortex with the blade causes an almost immediate loss in vortex core circulation. Downstream of the blade the core becomes embedded in the blade wake and begins to grow rapidly. Core radius increases and peak tangential velocity decreases but circulation remains roughly con stant. True turbulence levels within the core are much larger downstre am than upstream of the blade. Outside of the core the interaction pro duces a substantial region of turbulent flow associated with the blade and vortex generator wakes. Overall, perpendicular blade vortex inter action substantially alters the flow and produces a much larger and mo re intense region of turbulent flow than that presented by the undistu rbed vortex. These results have significant implications for the predi ction of both impulsive and broadband helicopter noise.