Aeroacoustics of Vertical Lift Ducted Rotors

Wook Rhee, Leighton Myers, Dennis McLaughlin
2009 15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference)   unpublished
Aeroacoustic experiments were conducted on a ducted lift fan model designed for new VSTOL vehicle applications. Such ducted fan models are being investigated with wind tunnel experiments at Penn State predominantly to determine their aerodynamic characteristics. A series of aeroacoustic experiments were also undertaken in an anechoic chamber. It is anticipated that the duct surrounding a rotor can potentially provide shielding for the aerodynamic noise produced by the rotor. The experiments
more » ... The experiments measured the radiated noise on a circular arc of approximately 3 rotor diameters from the nozzle. Three microphones were mounted on a boom that could be easily rotated over selected polar apertures. As expected, the acoustic spectra are dominated by tones at the blade passage frequency and its harmonics. The directivity of the noise is consistent with a mixture of dipole and quadrupole generated noise by the rotor blades, and the duct has little effect on the levels. When expressed on an equivalent thrust basis, the noise of the ducted fan is very close to the un-ducted one. It appears that noise reduction will only result from the installation of a perforated liner on the inside of the duct.
doi:10.2514/6.2009-3333 fatcat:hfeycekvq5h7de7m45ko6quh6m