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  • 1
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    Advanced measurement techniques, part 1 (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In modern laminar flow flight and wind tunnel research, it is important to understand the specific cause(s) of laminar to turbulent boundary layer transition. Such information is crucial to the exploration of the limits of practical application of laminar flow for drag reduction on aircraft. The process of transition involves both the possible modes of disturbance growth, and the environmental conditioning of the instabilities by freestream or surface conditions. The possible modes of disturbance growth include viscous, inviscid, and modes which may bypass these natural ones. Theory provides information on the possible modes of disturbance amplification, but experimentation must be relied upon to determine which of those modes actually dominates the transition process in a given environment. The results to date of research on advanced devices and methods used for the study of transition phenomena in the subsonic and transonic flight and wind tunnel environments are presented.
    Keywords: AERODYNAMICS
    Type: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 317-340
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    A study of the effects of Reynolds number and Mach number on constant pressure coefficient jump for shock-induced trailing-edge separation (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The influence of Mach and Reynolds numbers as well as airfoil and planform geometry on the phenomenon of constant shock jump pressure coefficient for conditions of shock induced trailing edge separation (SITES) was studied. It was demonstrated that the phenomenon does exist for a wide variety of two and three dimensional flow cases and that the influence of free stream Mach number was not significant. The influence of Reynolds number was found to be important but was not strong. Airfoil and planform geometric characteristics were found to be very important where the pressure coefficient jump was shown to vary with the sum of: (1) airfoil curvature at the upper surface crest, and (2) camber surface slope at the trailing edge. It was also determined that the onset of SITES could be defined as a function of airfoil geometric parameters and Mach number normal to the leading edge. This onset prediction was shown to predict the angle of onset to within + or - 1 deg accuracy or better for about 90% of the cases studied.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4090 , NAS 1.26:4090
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Flow quality measurements for the Langley 8-foot transonic pressure tunnel LFC experiment (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Laminar flow experiments were performed in an 8-foot transonic pressure tunnel which was modified in order to simulate the conditions of an infinite span yawed wing. A liner in the tunnel provided a flow field around the yawed airfoil. The results were evaluated using hot-wire and fluctuating pressure measurements. Data were obtained for root-mean-square fluctuations, their spectra, and various cross product terms.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0150
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Performance characteristics from wind-tunnel tests of a low-Reynolds-number airfoil (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnel lift and pitching-moment data have been obtained from pressure measurements, and drag data from wake surveys, for an Eppler 387 low Reynolds number airfoil over the Re range of 60,000 to 460,000; oil flow visualizations were also used to determine laminar separation and turbulent reattachment locations. Airfoil performance is found to be dominated by laminar separation bubbles below Re 200,000, and two flow regimes, namely laminar separations with and without turbulent reattachment, were observed at the same angle-of-attack for an Re of 60,000.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0607
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Low-speed aerodynamic characteristics of a twin-engine general aviation configuration with aft-fuselage-mounted pusher propellers (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted to determine the aerodynamic characteristics of an advanced turboprop aircraft model with aft-pylon-mounted pusher propellers. Tests were conducted through an angle-of-attack range of -8 to 28 degrees, and an angle-of-sideslip range of -20 to 20 degrees at free-stream conditions corresponding to Reynolds numbers of 0.55 to 2.14 x 10 to the 6th power based on mean aerodynamic chord. Test results show that for the unpowered configurations the maximum lift coefficients for the cruise, takeoff, and landing configurations are 1.45, 1.90, and 2.10, respectively. Nacelle installation results in a drag coefficient increase of 0.01. Increasing propeller thrust results in a significant increase in lift for angles of attack above stall and improves the longitudinal stability. The cruise configuration remains longitudinally stable to an angle of attack 5 degrees beyond the stall angle, the takeoff configuration is stable 4 degrees beyond stall angle, and the landing configuration is stable 3 degrees beyond stall angle. The predominant effect of symmetric thrust on the lateral-directional aerodynamic characteristics is in the post-stall region, where additional rudder control is available with power on.
    Keywords: AERODYNAMICS
    Type: NASA-TP-2763 , L-16331 , NAS 1.60:2763
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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