COMPUTATION AND MEASUREMENT OF THE FLOWFIELD NEAR A SWEPT ROTOR BLADE TIP IN HOVER

Navier-Stokes computations of the flowfield and surface pressure distribution are described for a rotor blade with a complex tip shape. The flowfield is also studied experimentally using laser sheet flow visualization, and measured in detail using laser Doppler velocimetry. The objective of this research is to understand the behavior of the flow over rotor tip shapes for use at high pitch angles, and to develop methods of improving retreating-blade performance in forward flight. Comparison of the computed results with results for a fixed wing show that the vortex system around the rotor tip is less sensitive to pitch angle variation, and remains organized at high pitch angles. Fairly good agreement is obtained between computed and measured velocity fields in the tip region, with the wake computation replaced by a simple pitch angle correction. There is no strong inboard vortex observed in either the computed or measured results.