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  • 1
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    Jet noise (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The main conclusions reached are: (1) At low subsonic jet exhaust velocities, jet noise varies as the velocity to the eighth power; (2) at high subsonic exhaust velocities, jet noise approaches a variation with velocity to the third power; (3) use of the jet density squared overcorrects density effects on jet noise; (4) subsonic and supersonic jet noise levels can be predicted; and (6) use of multielement nozzles and acoustically lined ejectors significantly suppress jet noise at intermediate jet exhaust velocities.
    Keywords: AIRCRAFT
    Type: Aircraft Engine Noise Reduction; p 103-137
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Helicopter engine core noise (1982)
    In:  CASI
    Details
    Publication Date: 2006-04-17
    Description: Calculated engine core noise levels, based on NASA Lewis prediction procedures, for five representative helicopter engines are compared with measured total helicopter noise levels and ICAO helicopter noise certification requirements. Comparisons are made for level flyover and approach procedures. The measured noise levels are generally significantly greater than those predicted for the core noise levels, except for the Sikorsky S-61 and S-64 helicopters. However, the predicted engine core noise levels are generally at or within 3 dB of the ICAO noise rules. Consequently, helicopter engine core noise can be a significant contributor to the overall helicopter noise signature.
    Keywords: ACOUSTICS
    Type: NASA. Langley Research Center Rotorcraft Noise; p 261-284
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    The icing problem: Current status of NACA techniques and research (1955)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: AGARD-AG-19/P9
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Peak axial-velocity decay with multi-element rectangular and triangular nozzles (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The aircraft noise created by the impingement of engine exhaust jet of STOL aircraft with externally blown flaps is discussed. It was determined that the jet-flap interaction noise can be lowered by reducing the impinging velocity of the jet. The reduction must occur at a specific distance from the flap to be effective. The peak axial-velocity decay obtained with rectangular and triangular single element mixer nozzles is presented. Equations are developed for estimating the peak axial velocity decay curves for a wide range of nozzle configurations.
    Keywords: AIRCRAFT
    Type: NASA-TM-X-68047
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Interim noise correlation for some OTW configurations using external jet-flow deflectors (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Jet flap interaction acoustic data obtained statically from a model-scale study of STOL-OTW configurations with a conical nozzle mounted above the wing and using various external deflectors to provide jet-flow attachment are correlated. The acoustic data are correlated in terms that consider the jet/flap interaction noise contributions associated primarily with fluctuating lift, trailing edge, and configuration wake noise sources. Variables considered include deflector geometry, flap setting and wing size. Finally, the configuration overall noise levels are related to static lift and thrust measurements in order to provide insight into possible acoustic/aerodynamic performance trade-off benefits.
    Keywords: ACOUSTICS
    Type: NASA-TM-73746 , E-9317 , Aeroacoustics Conf.; Oct 03, 1977 - Oct 05, 1977; Atlanta
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    OTW noise correlation for several nozzle/wing geometries using a 5:1 slot nozzle with external deflectors (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Acoustic spectral data obtained from a model-scale study of several over the wing (OTW) configurations with a 5:1 slot nozzle using various external deflectors are correlated in terms of deflector geometry and flow parameters. Variations in the deflector geometry include deflector size and deflector angle. In addition, geometry variations in flap setting and nozzle chordwise location are included. Three dominant noise sources are correlated: fluctuating lift noise, flap trailing edge noise, and jet mixing noise. Aerodynamic characteristics including lift and thrust measurements, obtained for the various configurations are summarized.
    Keywords: ACOUSTICS
    Type: NASA-TM-X-73529 , E-8949 , Meeting of the Acoustical Soc. of Am.; Nov 16, 1976 - Nov 19, 1976; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Velocity decay and acoustic characteristics of various nozzle geometries with forward velocity (1973)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Utilizing a static test stand, 6- by 9-foot wind tunnel and 13-inch circular free jet, aerodynamic and acoustic data were obtained with a convergent circular nozzle, bypass nozzle, 6-tube mixer nozzle, and velocity decay surveys with and without forward velocity. The acoustic data include total sound power, directivity and frequency spectra obtained statically and with forward velocity. The relation of aerodynamic and acoustic measurements statically and in forward flight for the various nozzle configurations are discussed.
    Keywords: FLUID MECHANICS
    Type: NASA-TM-X-68259 , E-7547 , Fluid and Plasma Dyn. Conf.; Jul 16, 1973 - Jul 18, 1973; Palm Springs,CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Acoustic results obtained with upper-surface-blowing lift augmentation systems (1972)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The noise caused by the interaction of the jet exhaust and a wing was measured under static conditions for several versions of a small-scale STOL engine-over-the-wing configuration. Three basic nozzles were used in the tests; a circular nozzle, a 5:1 aspect ratio slot nozzle and a 10:1 aspect ratio slot nozzle. Various flow attachment devices were included in the study. The wing included a flap that could be positioned for nominal takeoff or approach flap settings. Far field noise data are presented for the flyover mode. The data are discussed in terms of sound power and sound pressure spectra. Implications of extending the small-scale model acoustic data to full-scale aircraft are discussed briefly and indicate a sizeable flyover noise attenuation may be achieved due to shielding by the wing.
    Keywords: AIRCRAFT
    Type: NASA-TM-X-68159 , E-7215 , Meeting of the Acoust. Soc. of Am.; Nov 28, 1972 - Dec 01, 1972; Miami Beach, FL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Forward flight effects on mixer nozzle design and noise considerations for STOL externally blown flap systems. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 72-792 , American Institute of Aeronautics and Astronautics, Aircraft Design, Flight Test, and Operations Meeting; Aug 07, 1972 - Aug 09, 1972; Los Angeles, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Comparison of jet Mach number decay data with a correlation and jet spreading contours for a large variety of nozzles (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Small-scale circular, noncircular, single- and multi-element nozzles with flow areas as large as 122 sq cm were tested with cold airflow at exit Mach numbers from 0.28 to 1.15. The effects of multi-element nozzle shape and element spacing on jet Mach number decay were studied in an effort to reduce the noise caused by jet impingement on externally blown flap (EBF) STOL aircraft. The jet Mach number decay data are well represented by empirical relations. Jet spreading and Mach number decay contours are presented for all configurations tested.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-8423 , E-8561
    Format: application/pdf
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