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  • Aerodynamics  (4)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE  (3)
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  • 1
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    Geometric analysis of wing sections (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes a new geometric analysis procedure for wing sections. This procedure is based on the normal mode analysis for continuous functions. A set of special shape functions is introduced to represent the geometry of the wing section. The generators of the NACA 4-digit airfoils were included in this set of shape functions. It is found that the supercritical wing section, Korn airfoil, could be well represented by a set of ten shape functions. Preliminary results showed that the number of parameters to define a wing section could be greatly reduced to about ten. Hence, the present research clearly advances the airfoil design technology by reducing the number of design variables.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-110346 , A-950049 , NAS 1.15:110346
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.
    Keywords: Aerodynamics
    Type: 28th European Rotorcraft Forum; Sep 17, 2002 - Sep 20, 2002; Bristol, England; United Kingdom
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    The Prediction of Transonic Flows on an Advancing Rotor (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The object of this investigation was to find and demonstrate a means of performing efficient finite-difference computations of rotor loading for a trimmed rotor in high-speed, forward flight. The essence of the scheme that was developed is a loose-coupled iteration procedure between a finite difference and a comprehensive integral rotor code. The coupling involves a transfer of appropriate load and inflow data on the advancing side between the two codes such that consistency maintained. Sample computations, including a limited comparison with model rotor data, are presented. The scheme converges rapidly. However, even one iteration with this scheme can provide sufficient accuracy for many purposes.
    Keywords: Aerodynamics
    Type: May 01, 1984; Arlington, VA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Forced Diffusion of Trailing Vorticity from a Hovering Rotor (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: A small turbulence generating device was Attached near the tip of a hovering rotor blade In order to alter the structure of the trailing vortex. Stereo particle image velocimetry (PIV) images were used to quantify the wake behind the rotor blade during the first revolution. An analysis of the 3D-velocity field includes a method for accounting for vortex wander. The results show that a major change in the size and intensity of the trailing vortex can be achieved.
    Keywords: Aerodynamics
    Type: American Helicopter Society 57th Annual Forum and Technology Display; May 09, 2001 - May 11, 2001; Washington, DC; United States
    Format: text
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  • 5
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    Devices that Alter the Tip Vortex of a Rotor (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Small devices were attached near the tip of a hovering rotor blade 'in order to alter the structure and trajectory of the trailing vortex. Stereo particle image velocimetry (PIV) images were used to quantify the wake behind the rotor blade during the first revolution. A procedure for analyzing the 3D-velocity field is presented that includes a method for accounting for vortex wander. The results show that a vortex generator can alter the trajectory of the trailing vortex and that a major change in the size and intensity of the trailing vortex can be achieved by introducing a high level of turbulence into the core of the vortex.
    Keywords: Aerodynamics
    Type: NASA/TM-2001-209625 , NAS 1.15:209625 , A-00V0036
    Format: application/pdf
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  • 6
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    Aerodynamic design of a Coanda induced force and thruster anti-torque system (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A general method of analysis of the external and internal aerodynamics of a generic Coanda induced circulation anti-torque system is presented. The technique gives moment about the yaw axis and download induced on the boom as well as the force developed by an aft jet. The external flows including downwash, wake swirl and the boom circulation are considered. The internal flow and losses through the duct, fan, blown slots, cascades and nozzle are considered on a step-by-step basis. Limited comparison is made with open data where available.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AHS Annual Forum; May 06, 1991 - May 08, 1991; Phoenix, AZ; United States
    Format: text
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  • 7
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    Model tilt-rotor hover performance and surface pressure measurement (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A test of a small scale 3-bladed model rotor, with geometry typical of that used on tilt rotor aircraft, was conducted in the Army Aeroflightdynamics Directorate's anechoic hover chamber. The purpose was to determine the hover performance of the rotor and investigate the pressure distributions on a blade at various collective pitch angles and tip speeds. The measured pressures indicate that the rotor did not stall for high collective pitch angles up to theta sub c = 25 deg. This is clearly a 3-D effect since 2-D theory predicts flow separation at these high angles. The flow near the trailing edge separated above theta sub c = 25 deg which caused a sharp increase in power.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AHS, Annual Forum; May 21, 1990 - May 23, 1990; Washington, DC; United States
    Format: text
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