Wind tunnel

Physics

Lift (data mining)

Aerospace engineering

Reynolds number

Chord (peer-to-peer)

Pylon

Mechanics

Structural engineering

Propeller

Distributed computing

Aeroacoustics

Data mining

Fuselage

Aerodynamics

Aeroelasticity

Vortex

Engineering

Lift coefficient

Turbulence

Marine engineering

Acoustics

Particle image velocimetry

Turbine

Computer science

Sound pressure

Thrust

Blade pitch

Nacelle

Wake

Advance ratio

Journal of Aircraft

An experimental analysis was performed of the unsteady aerodynamic loading caused by the impingement of a propeller slipstream on a downstream lifting surface. When installed on an aircraft, this unsteady loading results in vibrations that are transmitted to the fuselage and are perceived inside the cabin as structure-borne noise. A pylon-mounted tractor–propeller configuration was installed in a low-speed wind tunnel at Delft University of Technology. Surface-microphone and particle-image-velocimetry measurements were taken to quantify the pressure fluctuations on the pylon and visualize the impingement phenomena. It was confirmed that the propeller tip vortex is the dominant source of pressure fluctuations on the pylon. Along the path of the tip vortex on the pylon, a periodic pressure response occurs with strong harmonics. The amplitude of the pressure fluctuations increases with increasing thrust setting, whereas the unsteady lift coefficient displays a nonmonotonic dependency on the propeller thrust. The lowest integral unsteady loads were obtained for cases with approximately integer ratios between the pylon chord and the wavelength of the perturbation associated with the propeller tip vortices. This implies that structure-borne-noise reductions might be obtained by matching the pylon chord with an integer multiple of the axial separation between the propeller tip vortices.

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers