Pressure-time history of pylon wake on a pusher propeller in flight

Abstract

Miniature, high-frequency, pressure transducers were mounted on a pusher propeller at 75 and 90% radii. Time history of fluctuating surface pressure over 700 propeller revolutions and 26 flight conditions reveals intriguing phenomena. The anticipated pylon wake signature manifests itself as a negative pressure pulse over extended portions of the propeller suction surface. The phenomenon further develops into a primarily random turbulence signature at 80% propeller chord and interestingly may re-evolve as a coherent wake signature further downstream, say at 90% chord. A new type of periodic disturbance of long-time scale, compared to propeller period of revolution, is discovered at positions beyond 0.6 chord on the propeller suction surface in the transonic regime. These and other peculiar propeller-surface events recorded by the transducers are highlighted, and some plausible explanations are offered.