Aerodynamics and Acoustics of Rectangular and Swept Rotor Blade Tips
Abstract:This paper presents some experimental and theoretical studies dealing with both acoustics and aerodynamics of helicopter rotor blades in high‐speed forward flight. Experimental results obtained in the S2Ch acoustically treated wind tunnel compare a rectangular blade tip to a parabolic sweptback tip with anhedral (designated PF1). The comparison shows an increase in the aerodynamic performance of the PF1 blades, which is due to a decrease of the transonic flow intensity an the advancing blade side. Calculations with a transonic small disturbance code show good agreement with experimental data. Acoustic measurements show a noise reduction for the PF1 blades. This trend was verified also through calculation. An analytical study evaluates the influence of blade tip shape on the generated thickness noise. Assessment of compressibility effects by quadrupolar noise calculations for several blade tips is presented; the limitations of the method are discussed.
Document Type: Research Article
Affiliations: Office National d'Etudes et de Recherches Ae´rospatiales, Chatillon, France
Publication date: January 1, 1989
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