FREQUENCY-DOMAIN ANALYSIS OF FLUCTUATING PRESSURE ON A PUSHER PROPELLER BLADE SURFACE

Chordwise distribution of unsteady surface pressure is measured on a pylon-mounted pusher propeller in flight. Spectral decomposition of the fluctuating surface pressure signals reveals a strong presence of upstream wake interaction. The growth and decay behavior of the fundamental disturbance wave along the propeller chord exhibits the same characteristics as a separated, reattaching shear layer. Frequency-domain analysis further suggests a single or multiple vortex-shedding phenomenon from the pusher propeller trailing edge, per revolution, in an upstream wake interaction. The rms amplitude of higher harmonics (i.e., k = 3, 4, 5, and 6) along the propeller chord attains values corresponding to boundary-layer random turbulence levels. Joint statistical properties between selected transducers on the propeller suction surface suggest a linear frequency response of the dynamical system to the fundamental and first harmonic disturbances, while higher-frequency Fourier components result in a nonlinear response behavior.