A study of rotor tip vortex structure alteration techniques

Numerical studies of the tip-vortex structure from a hovering rotor with bl owing are presented, and compared with the tip-vortex structure from a clea n rotor, and From a rotor using a passive trailing-edge tip device. A hybri d, Navier-Stokes potential Row method is used to model the flowfield. A sch eme 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 st udied at various planes behind the blade trailing edge. These data for the clean rotor are first compared with experimental results obtained for the s ame rotor. Previously published results for the tip-vortex structure from t he same rotor employing a passive tip device are discussed next. Finally, r esults for a rotor blade with upper and lower surface blowing are presented . It is concluded that the tip-vortex strength may be modified through blow ing. 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 ass ociated with spoilers.