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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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    Preliminary Results of Heat Transfer from a Stationary and Rotating Ellipsoidal Spinner (1953)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Convective heat-transfer coefficients in dry air were obtained for an ellipsoidal spinner of 30-inch maximum diameter for both stationary and rotating operation over a range of conditions including airspeeds up to 275 miles per hour, rotational speeds up to 1200 rpm, and angles of attack of zero and 40 The results are presented in terms of Nusselt numbers, Reynolds numbers, and convective heat-transfer coefficients. The studies included both uniform heating densities over the spinner and uniform surface temperatures.. In general, the results showed that rotation will increase the convective heat transfer from a spinner, especially in the turbulent-flow regions. Rotation of the spinner at 1200 rpm and at a free-stream velocity of 275 miles per hour increased the Nusselt number parameter in the turbulent-flow region by 32 percent over that obtained with a stationary spinner; whereas in the nose region, where the flow was laminar, an increase of only 18 percent was observed. Transition from laminar to turbulent flow occurred over a large range of Reynolds numbers primarily because of surface roughness of the spinner. Operation at an angle of attack of 40 had only small effects on the local convective heat transfer for the model studied.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NACA-RM-E53F02
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Preliminary Results of Cyclical De-Icing of a Gas-Heated Airfoil (1952)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An NACA 65(sub 1)-212 airfoil of 8-foot chord was provided with a gas-heated leading edge for investigations of cyclical de-icing. De-icing was accomplished with intermittent heating of airfoil segments that supplied hot gas to chordwise passages in a double-skin construction. Ice removal was facilitated by a spanwise leading-edge parting strip which was continuously heated from the gas-supply duct. Preliminary results demonstrate that satisfactory cyclical ice removal occurs with ratios of cycle time to heat-on period (cycle ratio) from 10 to 26. For minimum runback, efficient ice removal, and minimum total heat input, short heat-on periods of about 15 seconds with heat-off periods of 260 seconds gave the best results. In the range of conditions investigated, the prime variables in the determination of the required heat input for cyclical ice removal were the air temperature and the cycle ratio; heat-off period, liquid water content, airspeed, and angle of attack had only secondary effects on heat input rate.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NACA-RM-E51J29
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Some considerations of the need for icing protection of high-speed, high-altitude airplanes (1954)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-82265
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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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
  • 8
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    Noise suppression due to annulus shaping of an inverted-velocity-profile coaxial nozzle (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An inverted velocity profile coaxial nozzle for use with supersonic cruise aircraft produces less jet noise than an equivalent conical nozzle. Furthermore, decreasing the annulus height (increasing radius ratio with constant flow) results in further noise reduction benefits. The annulus shape (height) was varied by an eccentric mounting of the annular nozzle with respect to a conical core nozzle. Acoustic measurements were made in the flyover plane below the narrowest portion of the annulus and at 90 deg and 180 deg from this point. The model-scale spectra are scaled up to engine size (1.07 m diameter) and the perceived noise levels for the eccentric and baseline concentric inverted velocity profile coaxial nozzles are compared over a range of operating conditions. The implications of the acoustic benefits derived with the eccentric nozzle to practical applications are discussed.
    Keywords: ACOUSTICS
    Type: NASA-TM-81460 , E-389 , Meeting of the Acoust. Soc. of Am.; Apr 21, 1980 - Apr 25, 1980; Atlanta
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Acoustic considerations of flight effects on jet noise suppressor nozzles (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The inflight acoustic characteristics of high velocity jet noise suppressor nozzles for supersonic cruise aircraft were reviewed. The inflight effects at the peak noise level were discussed. Both single and inverted velocity profile multistream suppressor nozzles were considered. The importance of static spectral shape on the noise reduction due to inflight effects was stressed.
    Keywords: ACOUSTICS
    Type: NASA-TM-81377 , E-282 , AIAA PAPER 80-0164 , AIAA 18th Aerospace Sci. Meeting; Jan 14, 1980 - Jan 16, 1980; Pasadena, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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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
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