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  • AERODYNAMICS  (629)
  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1985-1989  (896)
  • 1975-1979
  • 1987  (896)
  • 1
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    The Aerodynamic Optimization of Wings at Subsonic Speeds and the Influence of Wingtip Design (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Some of the objectives of modern aircraft development are related to the achievement of reduced fuel consumption and aircraft noise. This investigation is mainly concerned with the aerodynamic aspects of aircraft development, i.e., reduction of induced drag. New studies of wing design, and in particular wing tips, are considered. Induced drag is important since, in cruising flight, it accounts for approximately one-third of the entire drag for the aircraft, and one-half while climbing. A survey is presented for the wing geometries and wing tip designs studied, and theoretical investigations of different planar wings with systematically varied wing tip forms are conducted. Attention is also paid to a theoretical study of some planar and nonplanar wings and their comparison with experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88534 , NAS 1.15:88534
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Integral method of wall interference correction in low-speed wind tunnels (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The analytical solution of Poisson's equation, derived form the definition of vortex, was applied to the calculation of interference velocities due to the presence of wind tunnel walls. This approach, called the Integral Method, allows an accurate evaluation of wall interference for separated or more complicated flows without the need for considering any features of the model. All the information necessary for obtaining the wall correction is contained in wall pressure measurements. The correction is not sensitive to normal data-scatter, and the computations are fast enough for on-line data processing.
    Keywords: AERODYNAMICS
    Type: NASA-TT-20055 , NAS 1.77:20055
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    A simple device for the preparation of embedded materials science specimens for ultramicrotomy (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A simple hand-held grinding fixture is discussed which can produce microtome mounts of hard materials, oriented interfaces, and powders embedded in a 5/16-in plastic rod. The device has been used for the ultramicrotomy of meteorite samples, 10-50 micron interplanetary dust particles, and thin films on plastic. Results are presented for a layer lattice silicate from the Murchison carbonaceous chondrite, illustrating the resolution and structural detail that can be obtained with the method.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Electron Microscopy Technique (ISSN 0741-0581); 6; 305
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Algorithm implementation on the Navier-Stokes computer (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Navier-Stokes Computer is a multi-purpose parallel-processing supercomputer which is currently under development at Princeton University. It consists of multiple local memory parallel processors, called Nodes, which are interconnected in a hypercube network. Details of the procedures involved in implementing an algorithm on the Navier-Stokes computer are presented. The particular finite difference algorithm considered in this analysis was developed for simulation of laminar-turbulent transition in wall bounded shear flows. Projected timing results for implementing this algorithm indicate that operation rates in excess of 42 GFLOPS are feasible on a 128 Node machine.
    Keywords: AERODYNAMICS
    Type: NASA-TM-89119 , NAS 1.15:89119
    Format: application/pdf
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  • 5
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    Control of shear flows by artificial excitation (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Investigations involving artificial excitation of various shear flows are reviewed. Potential applications of excitation in flow control, e.g., in enhancing mixing, and in delaying transition and separation are discussed. An account is given of the current activities at NASA Lewis Research Center in this regard.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-2722
    Format: text
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  • 6
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    Control of shear flows by artificial excitation (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Investigations involving artificial excitation of various shear flows are reviewed. Potential applications of excitation in flow control, e.g., in enhancing mixing, and in delaying transition and separation are discussed. An account is given of the current activities at NASA Lewis Research Center in this regard.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100201 , E-3794 , NAS 1.15:100201 , AIAA PAPER 87-2722
    Format: application/pdf
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  • 7
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    A natural low frequency oscillation in the wake of an airfoil near stalling conditions (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An unusually low frequency oscillation in the flow over an airfoil was explored experimentally. Wind tunnel measurements were carried out with a two dimensional airfoil model at a chord Reynolds number of 100,000. During deep stall the usual bluff-body shedding occurred at a Strouhal number. But at the onset of stall a low frequency periodic oscillation occurred, the corresponding Strouhal number being an order of magnitude lower. The phenomenon occurred in relatively unclean flow when the freestream turbulence was raised to 0.4 percent, but did not in the cleaner flow with turbulence intensity of 0.1 percent. It could also be produced by certain high frequency acoustic excitation. Details of the flow field are compared between a case of low frequency oscillation at alpha = 15 deg and a case of bluff-body shedding at alpha = 22.5 deg. The origin of the low frequency oscillation traces to the upper surface of the airfoil and is seemingly associated with the periodic formation and breakdown of a large separation bubble. The intense flow fluctuations impart significant unsteady forces to the airfoil but diminish rapidly within a distance of one chord from the trailing edge.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100213 , E-3822 , NAS 1.15:100213 , AIAA PAPER 88-0131
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  • 8
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    3-D axial blade row flow field inviscid finite volume prediction and verification (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A modification of the unsteady finite volume three-dimensional Euler scheme of Denton (1982) is developed to provide more accurate steady state solutions at enhanced convergence rates, and it is assessed for application to detailed axial blade row flow predictions by correlating predictions with data for a wide range of flow fields. Radial and pitchwise smoothing are minimized by the elimination of under-relaxing while time marching, by the addition of an internal transient averaging scheme, and by the use of the maximum stable local time step for each grid element. Results show that the flow field is accurately predicted in regions of primarily axial pressure gradients, though the predictions do not correlate well with the data in regions of strong nonaxial pressure gradients. Though the scheme is second order accurate in the axial direction, it is first order accurate in the other dimensions, smearing the flow field details.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0432
    Format: text
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  • 9
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    Transonic rotor flow-measurement technique using holographic interferometry (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Holographic interferometry is used to record interferograms of the flow near a hovering transonic rotor blade. A pulsed ruby laser recorded 40 interferograms with a 2 ft dia. view field near the model rotor blade tip operating at a tip Mach number of 0.90. The experimental procedure is presented and example interferograms recorded in the rotor's tip path plane. In addition, a method currently being pursued to obtain quantitative flow information using computer assisted tomography (CAT) with the holographic interferogram data, is outlined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Ames Research Center, Automated Reduction of Data from Images and Holograms; p 49-51
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  • 10
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    Reconstruction of a three-dimensional, transonic rotor flow field from holographic interferogram data (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Holographic interferometry and computerized aided tomography (CAT) are used to determine the transonic velocity field of a model rotor blade in hover. A pulsed ruby laser recorded 40 interferograms with a 2 ft dia view field near the model rotor blade tip operating at a tip Mach number of 0.90. After digitizing the interferograms and extracting the fringe order functions, the data are transferred to a CAT code. The CAT code then calculates the perturbation velocity in several planes above the blade surface. The values from the holography-CAT method compare favorably with previously obtained numerical computations in most locations near the blade tip. The results demonstrate the technique's potential for three dimensional transonic rotor flow studies.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center, Automated Reduction of Data from Images and Holograms; p 149-170
    Format: application/pdf
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