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  • 1
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    Wing laminar boundary layer in the presence of a propeller slipstream (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effects of a propeller slipstream on the wing laminar boundary layer are being investigated. Hot-wire velocity sensor measurements have been performed in flight and in a wind tunnel. It is shown that the boundary layer cycles between a laminar state and a turbulent state at the propeller blade passage rate. The cyclic length of the turbulent state increases with decreasing laminar stability. Analyses of the time varying velocity profiles show the turbulent state to lie in a transition region between fully laminar and fully turbulent. The observed cyclic boundary layer has characteristics similar to relaminarizing flow and laminar flow with external turbulence.
    Keywords: AERODYNAMICS
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    An investigation of the effects of the propeller slipstream of a laminar wing boundary layer (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A research program is in progress to study the effects of the propeller slipstream on natural laminar flow. Flight and wind tunnel measurements of the wing boundary layer have been made using hot-film velocity sensor probes. The results show the boundary layer, at any given point, to alternate between laminar and turbulent states. This cyclic behavior is due to periodic external flow turbulence originating from the viscous wake of the propeller blades. Analytic studies show the cyclic laminar/turbulent boundary layer to result in a significantly lower wing section drag than a fully turbulent boundary layer. The application of natural laminar flow design philosophy yields drag reduction benefits in the slipstream affected regions of the airframe, as well as the unaffected regions.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 850859
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Propeller slipstream/wing boundary layer effects at low Reynolds numbers (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effects of propeller slipstream on the wing laminar boundary are being investigated. Hot-wire velocity sensor measurements have been performed in flight and in a wind tunnel. It is shown that the boundary layer cycles between a laminar state and a turbulent state at the propeller blade passage rate. The cyclic length of the turbulent state increases with decreasing laminar stability. Analyses of the time varying velocity profiles show the turbulent state to lie in a transition region between fully laminar and fully turbulent. The observed cyclic boundary layer has characteristics similar to relaminarizing flow and laminar flow with external turbulence.
    Keywords: AERODYNAMICS
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    An experimental investigation of the aerodynamics and cooling of a horizontally-opposed air-cooled aircraft engine installation (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A flight-test based research program was performed to investigate the aerodynamics and cooling of a horizontally-opposed engine installation. Specific areas investigated were the internal aerodynamics and cooling mechanics of the installation, inlet aerodynamics, and exit aerodynamics. The applicable theory and current state of the art are discussed for each area. Flight-test and ground-test techniques for the development of the cooling installation and the solution of cooling problems are presented. The results show that much of the internal aerodynamics and cooling technology developed for radial engines are applicable to horizontally opposed engines. Correlation is established between engine manufacturer's cooling design data and flight measurements of the particular installation. Also, a flight-test method for the development of cooling requirements in terms of easily measurable parameters is presented. The impact of inlet and exit design on cooling and cooling drag is shown to be of major significance.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3405
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    An application of wake survey rakes to the experimental determination of thrust for a propeller driven aircraft (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The lack of slipstream static pressure distribution seriously affected the results but recommendations for removing the deficiency are discussed. The wake survey rake is shown to be a valuable tool in aircraft flight testing. Flow characteristics in the wake of the propeller were examined.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163920 , MSSU-EIRS-ASE-81-3
    Format: application/pdf
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  • 6
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    Investigation of a panel code for airframe/propeller integration analyses (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Hess panel code was investigated as a procedure to predict the aerodynamic loading associated with propeller slipstream interference on the airframe. The slipstream was modeled as a variable onset flow to the lifting and nonlifting bodies treated by the code. Four sets of experimental data were used for comparisons with the code. The results indicate that the Hess code, in its present form, will give valid solutions for nonuniform onset flows which vary in direction only. The code presently gives incorrect solutions for flows with variations in velocity. Modifications to the code to correct this are discussed.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-CR-166450 , NAS 1.26:166450
    Format: application/pdf
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  • 7
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    Propeller propulsion integration, phase 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A bibliography was compiled of all readily available sources of propeller analytical and experimental studies conducted during the 1930 through 1960 period. A propeller test stand was developed for the measurement of thrust and torque characteristics of full scale general aviation propellers and installed in the LaRC 30 x 60 foot full scale wind tunnel. A tunnel entry was made during the January through February 1980 period. Several propellers were tested, but unforseen difficulties with the shaft thrust torque balance severely degraded the data quality.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-163921 , MSSU-EIRS-ASE-81-4
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Investigation of helicopter rotor blade/wake interactive impulsive noise (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An analysis of the Tip Aerodynamic/Aeroacoustic Test (TAAT) data was performed to identify possible aerodynamic sources of blade/vortex interaction (BVI) impulsive noise. The identification is based on correlation of measured blade pressure time histories with predicted blade/vortex intersections for the flight condition(s) where impulsive noise was detected. Due to the location of the recording microphones, only noise signatures associated with the advancing blade were available, and the analysis was accordingly restricted to the first and second azimuthal quadrants. The results show that the blade tip region is operating transonically in the azimuthal range where previous BVI experiments indicated the impulsive noise to be. No individual blade/vortex encounter is identifiable in the pressure data; however, there is indication of multiple intersections in the roll-up region which could be the origin of the noise. Discrete blade/vortex encounters are indicated in the second quadrant; however, if impulsive noise were produced here, the directivity pattern would be such that it was not recorded by the microphones. It is demonstrated that the TAAT data base is a valuable resource in the investigation of rotor aerodynamic/aeroacoustic behavior.
    Keywords: AERODYNAMICS
    Type: NASA-CR-177435 , NAS 1.26:177435
    Format: application/pdf
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  • 9
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    Practical flight test method for determining reciprocating engine cooling requirements (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is pointed out that efficient and effective cooling of air-cooled reciprocating aircraft engines is a continuing problem for the general aviation industry. Miley et al. (1981) have reported results of a study regarding the controlling variables for cooling and installation aerodynamics. The present investigation is concerned with experimental methods which were developed to determine cooling requirements of an instrumented prototype or production aircraft, taking into account a flight test procedure which has been refined and further verified with additional testing. It is shown that this test procedure represents a straightforward means of determining cooling requirements with minimal instrumentation. Attention is given to some background information, the development history of the NACA cooling correlation method, and the proposed modification of the NACA cooling correlation.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Journal of Aircraft (ISSN 0021-8669); 21; 936-942
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    An experimental investigation of vortex stability, tip shapes, compressibility, and noise for hovering model rotors (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Schlieren methods of flow visualization and hot-wire anemometry for velocity measurements were used to investigate the wakes generated by hovering model propellers and rotors. The research program was directed toward investigating (1) the stability of the tip vortex, (2) the effects produced by various tip shapes on performance and tip vortex characteristics, and (3) the shock formation and noise characteristics associated with various tip shapes. A free-wake analysis was also conducted for comparison with the vortex stability experimental results. Schlieren photographs showing wake asymmetry, interaction, and instability are presented along with a discussion of the effects produced by the number of blades, collective pitch, and tip speed. Two hot-wire anemometer techniques, used to measure the maximum circumferential velocity in the tip vortex, are discussed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2305 , BELL-299-099-641
    Format: application/pdf
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