Accession Number : AD0734433

Title :   Vortex Shedding Noise of an Isolated Airfoil.

Descriptive Note : Final rept. 30 Jun 69-28 Dec 71,

Corporate Author : UNITED AIRCRAFT RESEARCH LABS EAST HARTFORD CONN

Personal Author(s) : Paterson,Robert W. ; Vogt,Paul G. ; Fink,Martin R. ; Munich,C. Lee

Report Date : DEC 1971

Pagination or Media Count : 118

Abstract : The purpose of the study was to determine the vortex shedding noise characteristics of isolated airfoils in a Reynolds number range applicable to full-scale helicopter rotors. Measurements of far-field noise, airfoil surface pressure fluctuations, and correlation coefficients were obtained for three airfoils. Two models of differing thickness were tested as two-dimensional models (NACA 0012 and 0018 airfoils) and the third has a span of half the tunnel width (NACA 0012 airfoil). Airfoil vortex shedding noise was found to be discrete rather than broadband. The frequency dependence of this noise on velocity and chord was found to be well predicted by a constant Strouhal number near 0.2 referenced to laminar wake thickness at the airfoil trailing edge. The presence of a laminar boundary layer on the pressure surface of the airfoils was found to be critical to the presence of vortex shedding noise. (Author)

Descriptors :   (*HELICOPTER ROTORS, *PROPELLER NOISE), (*BLADE AIRFOILS, *VORTICES), AERODYNAMIC NOISE, MODEL TESTS, WIND TUNNEL MODELS, ACOUSTICS, FREQUENCY, LAMINAR BOUNDARY LAYER, VELOCITY

Subject Categories : Aerodynamics
      Helicopters
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE