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  • 1985-1989  (6)
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Year
  • 1
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    Unknown
    Airfoil trailing-edge flow measurements (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 1245-125
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Unknown
    Reduction of background noise induced by wind tunnel jet exit vanes (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The NASA-Langley 4 x 7 m wind tunnel develops low frequency flow pulsations at certain velocity ranges during open throat mode operation, affecting the aerodynamics of the flow and degrading the resulting model test data. Triangular vanes attached to the trailing edge of flat steel rails, mounted 10 cm from the inside of the jet exit walls, have been used to reduce this effect; attention is presently given to methods used to reduce the inherent noise generation of the vanes while retaining their pulsation reduction features.
    Keywords: ACOUSTICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 1631
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Unknown
    Scaling of airfoil self-noise using measured flow parameters (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Data from an airfoil broadband self-noise study are reported. Attention here is restricted to two-dimensional models at zero angle of attack to the flow. The models include seven NACA 0012 airfoil sections and five flat plate sections with chordlengths ranging from 2.54 to 60.96 cm. Testing parameters include flow velocity to 71.3 m/s and boundary-layer turbulence through natural transition and by tripping. Detailed aerodynamic measurements are conducted in the near-wake of the sharp trailing edges. The noise spectra of the self-noise sources are determined by the use of a cross-spectral technique. The acoustic data are normalized using the measured aerodynamic parameters in order to evaluate a commonly used scaling law. An examination of the Reynolds number dependence of the normalized overall levels has revealed a useful scaling result. This result appears to quantify the transition between turbulent boundary-layer trailing-edge noise and laminar boundary-layer vortex shedding noise.
    Keywords: ACOUSTICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 207-213
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Unknown
    Airfoil tip vortex formation noise (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: ACOUSTICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 246-252
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Unknown
    A directional array approach for the measurement of rotor noise source distributions with controlled spatial resolution (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A special array system has been designed to examine noise source distributions over a helicopter rotor model. The particular measurement environment is for a rotor operating in the open jet of an anechoic wind tunnel. An out-of-flow directional microphone element array is used with a directivity pattern whose major directional lobe projects on the rotor disk. If significant contributions from extraneous tunnel noise sources in the direction of the side lobes are excluded, the dominant output from the array would be that noise emitted from the projected area on the rotor disk. The design incorporates an array element signal blending features which serves to control the spatial resolution of the size of the directional lobes. (Without blending, the resolution and side lobe size are very strong functions of frequency, which severely limits the array's usefulness).
    Keywords: AERODYNAMICS
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 112; 192-197
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Reduction of Vane Noise in Wind-Tunnel Nozzles (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Vane-induced noise reduced by adhering thin layer of porous material such as foam to downwind surface of vanes, particularly near sharp trailing edges, to prevent occurrence of edge tones. Other modifications made to aerodynamically streamline vane structure were rounding leading edges and smoothly fairing trailing edges. Boundary layer trip applied to leading edge to prevent laminar tone shedding from trailing edge.
    Keywords: MECHANICS
    Type: LAR-13333 , NASA Tech Briefs (ISSN 0145-319X); 9; 4; P. 143
    Format: text
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    NASA TECHNICAL REPORTS
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