A study of rotor tip vortex structure alteration techniques

Numerical studies of the tip-vortex structure from a hovering rotor with blowing are presented, and compared with the tip-vortex structure from a clean rotor, and From a rotor using a passive trailing-edge tip device. A hybrid, Navier-Stokes potential Row method is used to model the flowfield. A scheme that is fifth-order accurate in space is used to accurately capture the tip vortices. Velocity and vorticity data in the core of the vortex are studied at various planes behind the blade trailing edge. These data for the clean rotor are first compared with experimental results obtained for the same rotor. Previously published results for the tip-vortex structure from the same rotor employing a passive tip device are discussed next. Finally, results for a rotor blade with upper and lower surface blowing are presented. It is concluded that the tip-vortex strength may be modified through blowing. Blowing is found to be just as effective as a spoiler in altering the tip-vortex strength, but does not have the high drag and torque penalty associated with spoilers.