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    Surface pressure measurements at two tips of a model helicopter rotor in hover (1980)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Surface pressures were measured near the tip of a hovering single-bladed model helicopter rotor with two tip shapes. The rotor had a constant-chord, untwisted blade with a square, flat tip which could be modified to a body-of-revolution tip. Pressure measurements were made on the blade surface along the chordwise direction at six radial stations outboard of the 94 percent blade radius. Data for each blade tip configuration were taken at blade collective pitch angles of 0, 6.18 and 11.4 degrees at a Reynolds number of 736,000 and a Mach number of 0.25 both based on tip speed. Chordwise pressure distributions and constant surface pressure contours are presented and discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-3281
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    Exploratory investigation of sound pressure level in the wake of an oscillating airfoil in the vicinity of stall (1972)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Wind tunnel tests were performed on two oscillating two-dimensional lifting surfaces. The first of these models had an NACA 0012 airfoil section while the second simulated the classical flat plate. Both of these models had a mean angle of attack of 12 degrees while being oscillated in pitch about their midchord with a double amplitude of 6 degrees. Wake surveys of sound pressure level were made over a frequency range from 16 to 32 Hz and at various free stream velocities up to 100 ft/sec. The sound pressure level spectrum indicated significant peaks in sound intensity at the oscillation frequency and its first harmonic near the wake of both models. From a comparison of these data with that of a sound level meter, it is concluded that most of the sound intensity is contained within these peaks and no appreciable peaks occur at higher harmonics. It is concluded that within the wake the sound intensity is largely pseudosound while at one chord length outside the wake, it is largely true vortex sound. For both the airfoil and flat plate the peaks appear to be more strongly dependent upon the airspeed than on the oscillation frequency. Therefore reduced frequency does not appear to be a significant parameter in the generation of wake sound intensity.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA-CR-1948
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 3
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    Generation and development of a viscous vortex ring. (1972)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The vorticity transport and definition of vorticity equations are derived for an axisymmetric incompressible viscous vortex ring. The coupled system is solved numerically by the Peaceman-Rachford method and the method of successive over-relaxation. Instantaneous streaklines, velocity vector fields, vorticity contours, and streamline patterns offer a detailed picture of vortex ring generation. Results compare well with experimental observations of the behavior of viscous vortex rings. The radius, trajectory, and velocity of the ring are calculated and employed to predict the propagation velocity of the vortex ring using the vortex models of Helmholtz and Hill.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA PAPER 72-151 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 17, 1972 - Jan 19, 1972; San Diego, CA
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
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