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  • 1
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    Unsteady separation experiments on 2-D airfoils, 3-D wings, and model helicopter rotors (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Information on unsteady separation and dynamic stall is being obtained from two experimental programs that have been underway at United Technologies Research Center since 1984. The first program is designed to obtain detailed surface pressure and boundary layer condition information during high amplitude pitching oscillations of a large (17.3 in. chord) model wing in a wind tunnel. The second program involves the construction and testing of a pressure-instrumented model helicopter rotor. This presentation describes some of the results of these experiments, and in particular compares the detailed dynamic stall inception information obtained from the oscillating wing with the unsteady separation and reverse flow results measured on the retreating blade side of the model rotor during wind tunnel testing.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center, Physics of Forced Unsteady Separation; p 1-22
    Format: application/pdf
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  • 2
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    Airfoil stall penetration at constant pitch rate and high Reynolds number (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The model wing consists of a set of fiberglass panels mounted on a steel spar that spans the 8 ft test section of the UTRC Large Subsonic Wind Tunnel. The first use of this system was to measure surface pressures and flow conditions for a series of constant pitch rate ramps and sinusoidal oscillations a Mach number range, a Reynolds number range, and a pitch angle range. It is concluded that an increased pitch rate causes stall events to be delayed, strengthening of the stall vortex, increase in vortex propagation, and increase in unsteady airloads. The Mach number range causes a supersonic zone near the leading edge, stall vortex to be weaker, and a reduction of unsteady airloads.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Unsteady Aerodynamics and Aeroelasticity 1987, Part 2; p 519-542
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  • 3
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    Unsteady transition measurements on a pitching three-dimensional wing (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Boundary layer transition measurements were made during an experimental study of the aerodynamics of a rectangular wing undergoing unsteady pitching motions. The wing was tested at chordwise Mach numbers between 0.2 and 0.6, at sweep angles of 0, 15, and 30 deg, and for steady state, sinusoidal, and constant pitch rate motions. The model was scaled to represent a full size helicopter rotor blade, with chord Reynolds numbers between 2 and 6 x 10(exp 6). Sixteen surface hot-film gages were located along three spanwise stations: 0.08, 0.27, and 0.70 chords from the wing tip. Qualitative heat transfer information was obtained to identify the unsteady motion of the point of transition to turbulence. In combination with simultaneous measurements of the unsteady surface pressure distributions, the results illustrate the effects of compressibility, sweep, pitch rate, and proximity to the wing tip on the transition and relaminarization locations.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: California State Univ., The Fifth Symposium on Numerical and Physical Aspects of Aerodynamic Flows; 14 p
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  • 4
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    Incipient torsional stall flutter aerodynamic experiments on a swept three-dimensional wing (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The aerodynamics of small amplitude pitching motions near stall have been studied experimentally in order to improve understanding of the torsional stall flutter problem for propeller blades. A model wing was oscillated in pitch at several small amplitudes over a wide and representative range of conditions. Unsteady surface pressures were measured and integrated to determine the aerodynamic damping at five spanwise stations. Strong negative damping was found for motions centered near static stall for all studied reduced frequencies, Mach numbers, and sweep angles. The 30-deg sweptback configuration was found to become negatively damped over the entire span nearly simultaneously, while the unswept model exhibited local regions of negative damping that moved toward the wing tip as the mean angle of attack was increased.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0935 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Apr 08, 1991 - Apr 10, 1991; Baltimore, MD; United States
    Format: text
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