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Aeroacoustics of a rotor ingesting a planar boundary layer at high thrust

Published online by Cambridge University Press:  04 July 2018

Henry H. Murray IV*
Affiliation:
Center for Renewable Energy and Aerodynamic Technology, Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
William J. Devenport
Affiliation:
Center for Renewable Energy and Aerodynamic Technology, Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
W. Nathan Alexander
Affiliation:
Center for Renewable Energy and Aerodynamic Technology, Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
Stewart A. L. Glegg
Affiliation:
Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431, USA
David Wisda
Affiliation:
Center for Renewable Energy and Aerodynamic Technology, Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
*
Email address for correspondence: henryiv4@vt.edu

Abstract

Aeroacoustic measurements and analysis have been made for an unshrouded rotor partially immersed in a planar equilibrium turbulent boundary layer at low Mach number. This configuration provides an idealized model of inflow distortion effects seen when a rotor is mounted adjacent to the hull or fuselage of a vehicle. At low and moderate thrust conditions, the rotor produces broadband noise organized into haystacks produced by large eddies of the ingested turbulence being cut multiple times by successive rotor blades. At high thrust, however, the acoustic signature changes and becomes louder and more tonal. This change is accompanied by separation of the boundary layer from the wall in the vicinity of the rotor blade disk. The separation region is highly unsteady and populated by intense vortex structures. Acoustic analysis suggests that blade–vortex interactions with these structures are the source of the additional tonal noise at high thrust.

Type
JFM Papers
Copyright
© 2018 Cambridge University Press 

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