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  • AERODYNAMICS  (1.592)
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  • 2015-2019
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  • 1
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    Sparsely-sampled phase-insensitive two-dimensional arrays: Spatial interpolation and signal-dependent aperture (1987)
    In:  CASI
    Details
    Publikationsdatum: 2004-10-30
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NDE at NASA Langley. Advancing the State-of-the-Art and Providing a Quantitative Science Base for Materials Characterization; 10 p
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  • 2
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    Conservative full-potential model for unsteady transonic rotor flows (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 193-198
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  • 3
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    Mercury cadmium telluride short- and medium-wavelength infrared staring focal plane arrays (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Short and medium IR wavelength 64 x 64 hybrid focal plane arrays (FPAs) have been developed using sapphire-grown HgCdTe. The short wavelength arrays were developed for a prototype airborne imaging spectrometer, while those of medium wavelength are suitable for tactical missile seekers and strategic surveillance systems. Attention is presently given to results obtained for these FPAs' current-voltage characteristics, as well as for their characterization at different temperatures. The detector arrays were also mated to a multiplexer and characterized under different operating conditions. The unit cell size used is 52 x 52 microns.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering (ISSN 0091-3286); 26; 201-208
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  • 4
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    Phase closure with a rotational shear interferometer (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A simple and efficient way is proposed for achieving phase closure in an optical telescope (to enable recovering Fourier transform phases that would otherwise be corrupted by atmospheric and instrumental errors), by means of rotational shear interferometry. In a rotational shear interferometer, one images the telescope aperture onto the interferometer and then interferes the aperture with itself in a rotated orientation. To achieve the maximum frequency content permitted by the telescope, the shear has to be 180 deg, but better dynamic range and SNR are possible for lower frequencies. Drawbacks of the proposed method compared to radio astronomy are noted, and different approaches are indicated as to how to collect and use the phase closure data. Phase closure can be realized on existing telescopes and existing interferometers with special modifications. Although not all base lines are possible, the extra constraints provided by the closure phases greatly reduce the ambiguity now existing in phaseless image reconstruction.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics (ISSN 0003-6935); 26; 197-199
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  • 5
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    Numerical modeling of the vortex/airfoil interaction (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A modeling of the vortex-airfoil interaction is presented in which the finite-area of the real vortices is taken into consideration. Two vortex models are used. In the first, a disturbed piece of vorticity layer is simulated by four rows of discrete vortices of small strength. In the second, a number of discrete vortices is arranged within a circle. The first model may simulate a shear layer or a wake, while the second, a well-formed vortex. The method was applied to the calculation of the pressure induced on the surface of the airfoil by the interacting vortex. Both models give similar results. It was found that for large distances of the vortex from the surface of the airfoil, the consideration or not of the finite-area of the vortex is not a significant factor in determining the induced pressure field. However, when the distance of the vortex from the surface is reduced, its shape is distorted and the induced pressure pulses have lower amplitude than the ones induced by an equivalent point vortex. In the limit, where the vortex impinges on the leading edge of the airfoil, it is split into two and the time dependent pressure coefficient takes even negative values at some time intervals.
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 5-11
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  • 6
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    Numerical investigation of unsteady inlet flowfields (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 75-81
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  • 7
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    Hypersonic merged-layer flow on a sphere (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 1; 21-27
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  • 8
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    Theoretical analysis of aircraft afterbody flow (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Computational methods solving the thin shear layer formulation of the compressible, Reynolds-averaged Navier-Stokes equations are presently used to investigate the strongly interactive flow field about aircraft afterbodies. Solutions for a variety of axisymmetric afterbody and nozzle geometries are solved by means of a time-dependent implicit numerical algorithm for both subsonic and supersonic external flows, and the results obtained are compared with experimental data. A novel adaptive-grid technique is used to resolve flow regimes having large gradients, as well as to improve the accuracy and efficiency of the computational scheme.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 496-503
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  • 9
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    Simultaneous sampling technique for two spectral sources (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A technique is described that uses a bundle of fiber optics to simultaneously sample a dye laser and a spectral lamp. By the use of a real-time display with this technique, the two signals can be superimposed, and the effect of any spectral adjustments can be immediately accessed. In the NASA's CARS system used for combustion diagnostics, the dye laser mixes with a simultaneously pulsed Nd:YAG laser at 532 nm to probe the vibrational levels of nitrogen. An illustration of the oscilloscopic display of the system is presented.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Spectroscopy (ISSN 0003-7028); 41; 6, 19
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  • 10
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    Efficient self-consistent viscous-inviscid solutions for unsteady transonic flow (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 737-744
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  • 11
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    Application of axisymmetric analog for calculating heating in three-dimensional flows (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 296-302
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  • 12
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    Prospects for destructive self-induced interactions in a vortex pair (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 433-440
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  • 13
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    Influence of forebody cross-sectional shape on wing vortex-burst location (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 645-652
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  • 14
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    Aerothermodynamics of transatmospheric vehicles (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 594-602
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  • 15
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    Four-shooter - A large format charge-coupled device camera for the Hale telescope (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The Hale telescope has employed an astronomical camera using four 800x800 CCDs in an optical arrangement that allows the imaging of a contiguous 1600-pixel-square region of the sky; reimaging optics are then used to yield a scale of 0.33 arcsec/pixel. Optical coatings are incorporated to yield a throughput at peak efficiency of nearly 50 percent, including telescope losses. This camera can be used in a scanning mode, in which the telescope tracking rate is offset and the charge is clocked in the chips in such a way that the charge image remains aligned with the optical image. Attention is given to the results of a survey for high-redshift quasars using this equipment, which has produced images for the most distant galaxy clusters yet discovered.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering (ISSN 0091-3286); 26; 779-787
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  • 16
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    Scientific charge-coupled devices (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The charge-coupled device dominates an ever-increasing variety of scientific imaging and spectroscopy applications. Recent experience indicates, however, that the full potential of CCD performance lies well beyond that realized in devices currently available.Test data suggest that major improvements are feasible in spectral response, charge collection, charge transfer, and readout noise. These properties, their measurement in existing CCDs, and their potential for future improvement are discussed in this paper.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering (ISSN 0091-3286); 26; 692-714
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  • 17
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    Charge-coupled-device response to electron beam energies of less than 1 keV up to 20 keV (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent developments of backside treatment for the backside-illuminated scientifc CCD imagers have shown near-theoretical efficiency even at the short wavelength region of the spectrum. By using SEM performance comparisons of backside-treated and untreated CCDs to an electron flux varying from 1 to 100 pA and beam energy ranging from less than 1 keV up to 20 keV are obtained. The theoretical analysis, the SEM testing procedure, and the quantum efficiency measurement results are presented. It is shown, for example, that the average quantum efficiency increases from less than 1 percent for an untreated CCD to nearly 40 percent for a backside-treated CCD at a beam energy of 1 kev.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optical Engineering (ISSN 0091-3286); 26; 686-691
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  • 18
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    Vortical flow management techniques (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The aerodynamic performance and controllability of advanced, highly maneuverable supersonic aircraft can be enhanced by means of 'vortex management', which refers to the purposeful manipulation and reordering of stable and concentrated vortical structures due to flow separations from highly swept leading edges and slender forebodies at moderate-to-high angles-of-attack. Attention is presently given to a variety of results obtained in the course of experiments on generic research models at NASA Langley, clarifying their underlying aerodynamics and evaluating their performance-improvement potential. The vortex-management concepts discussed encompass aerodynamic compartmentation of highly swept leading edges, vortex lift augmentation and modulation, and forebody vortex manipulation.
    Schlagwort(e): AERODYNAMICS
    Materialart: Progress in Aerospace Sciences (ISSN 0376-0421); 24; 3, 19; 173-224
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  • 19
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    'Oxide-free' tip for scanning tunneling microscopy (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A new tip for scanning tunneling microscopy and a tip repair procedure that allows one to reproducibly obtain atomic images of highly oriented pyrolytic graphite with previously inoperable tips are reported. The tips are shown to be relatively oxide-free and highly resistant to oxidation. The tips are fabricated with graphite by two distinct methods.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Physics Letters (ISSN 0003-6951); 51; 305-307
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  • 20
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    Lower-upper implicit scheme for high-speed inlet analysis (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: (Previously cited in issue 20, p. 2915, Accession no. A86-42687)
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 1052
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  • 21
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    A thermal emission spectrometer for field use (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A field portable spectrometer has been built at the Jet Propulsion Laboratory which is suitable for collecting data relevant to remote sensing applications in the 4.7- to 5.6- and 8- to 12-micrometer atmospheric windows. The instrument employs a single cooled HgCdTe detector and a continuously variable filter wheel analyzer. The spectral range covered is 5- to 14.5-micrometers and the resolution is approximately 1.5 percent of the wavelength. A description of the hardware is followed by a discussion of the data processing steps leading to emissivity and radiance spectra. A section is devoted to the evaluation of the instrument performance with respect to spectral resolution, radiometric precision, and accuracy. Several examples of spectra acquired in the field are included.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 53; 627-632
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  • 22
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    Surface contamination monitoring by the measurement of scattering distribution functions (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper describes the use of Bidirectional Scattering Distribution Functions (BSDF) to quantify surface degradation, thus providing an effective method for contamination monitoring. This approach to contamination monitoring is based on the use of witness surfaces (mirrors or glass slides) located next to the critical surfaces. Contaminant accretion can be monitored during all phases of spacecraft fabrication, assembly, and testing. The method can be applied in other areas of contamination control such as monitoring of clean room environments. The BSDF can also prove extremely useful in establishing contamination control requirements and acceptability criteria. This paper describes the apparatus adopted to perform BSDF measurements and discusses some practical aspects of data collection. The results obtained in contamination monitoring programs performed at the NASA Goddard Space Flight Center are presented. Some possible new applications of this monitoring technique are also addressed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Environmental Sciences (ISSN 0022-0906); 30; 34-37
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  • 23
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    Energy-gap spectroscopy of superconductors using a tunneling microscope (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Physics Letters (ISSN 0003-6951); 50; 1921-192
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  • 24
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    Flow visualization study of the effect of injection hole geometry on an inclined jet in crossflow (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A flow visualization was studied by using neutrally buoyant, helium-filled soap bubbles, to determine the effect of injection hole geometry on the trajectory of an air jet in a crossflow and to investigate the mechanisms involved in jet deflection. Experimental variables were the blowing rate, and the injection hole geometry cusp facing upstream (CUS), cusp facing downstream (CDS), round, swirl passage, and oblong. It is indicated that jet deflection is governed by both the pressure drag forces and the entrainment of free-stream fluid into the jet flow. For injection hole geometries with similar cross-sectional areas and similar mass flow rates, the jet configuration with the larger aspect ratio experienced a greater deflection. Entrainment arises from lateral shearing forces on the sides of the jet, which set up a dual vortex motion within the jet and thereby cause some of the main-stream fluid momentum to be swept into the jet flow. This additional momentum forces the jet nearer the surface. Of the jet configurations, the oblong, CDS, and CUS configurations exhibited the largest deflections. The results correlate well with film cooling effectiveness data, which suggests a need to determine the jet exit configuration of optimum aspect ratio to provide maximum film cooling effectiveness.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 25
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    Reconstruction techniques of holograms from Spacelab 3 (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Fluid transport effects in a ground-based laboratory are fairly well known. Bouyancy driven transport occurs when there is a local density change in the fluid. In a low-g environment these density changes become less important, and other transport mechanisms dominate. To better understand fluid flows in a low-g environment, a fluid experiment system (FES) was designed to fly aboard the Shuttle orbiter in Spacelab. The FES is a holographic system designed for acquisition of the maximum amount of data from an experiment. The FES flew for the first time in May 1985 on Spacelab 3 for investigation of triglycine sulfate (TGS) crystal growth in low-g. This paper describes the FES optical system. The reconstruction techniques of the holograms are examined in detail, and the multiuser and reflight capabilities are discussed. Proposed future experiments are mentioned.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics (ISSN 0003-6935); 26; 2465-247
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  • 26
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    Multichannel optical correlator/convolver utilizing the magnetooptic spatial light modulator (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The paper describes a multichannel correlator/convolver architecture utilizing an acoustooptic light modulator for the one dimensional channel and a magnetooptic spatial light modulator (MOSLM) for the second two-dimensional parallel channel. The MOSLM allows greater parallelism to be implemented in this correlator/convolver design than was previously reported. The implementation of 24 parallel channels with a 48 x 48 device is demonstrated. Experimental data are presented and the ways of increasing the number of parallel channels using commercially available MOSLMs and other previously discussed techniques, such as frequency multiplexing, are discussed. It is shown that over 2000 parallel channels are possible at 32-bit accuracy. A technique for obtaining a limited gray scale is also discussed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics (ISSN 0003-6935); 26; 2479-248
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  • 27
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    Precision ozone calibration system based on vapor pressures of ozone (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A precision ozone calibration system for stratospheric research has been developed and evaluated. Vapor pressures above solid ozone are mixed with a carrier gas (N2) to produce stratospheric ozone mixing ratios at total pressures of 1 to cover 20 torr. The uncertainty in the ozone mixing ratios is approximately + or - 1.5 percent, the stability of ozone is + or - 0.3 percent. Experiments to be calibrated may sample the gas mixture over a wide range of flow rates; the maximum throughput of gas with corrections of less than 1 percent to ozone is about 200 torr 1/min. A mass spectrometer system continuously monitors the purity and stability of the N2-O3 gas mixture.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Review of Scientific Instruments (ISSN 0034-6748); 58; 1063-106
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  • 28
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    Computer controlled facility for measurement of the bidirectional scattering distribution function (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A computer controlled facility for measurement of the bidirectional scattering distribution function is described, with application to the evaluation of spacecraft surface contamination in optical and thermal control systems. An automatic detector/sampleholder allows a 360-deg detector scan around the sample for a complete bidirectional reflectance and transmittance distribution function characterization. The system demonstrates reduced data acquisition and reduction cycle time, and improved accuracy.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics (ISSN 0003-6935); 26; 25
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  • 29
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    Calculation of external-internal flow fields for mixed-compression inlets (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Supersonic inlet flows with mixed external-internal compressions were computed using a combined implicit-explicit (Beam-Warming-Steger/MacCormack) method for solving the three-dimensional unsteady, compressible Navier-Stokes equations in conservation form. Numerical calculations were made of various flows related to such inlet operations as the shock-wave intersections, subsonic spillage around the cowl lip, and inlet started versus unstarted conditions. Some of the computed results were compared with wind tunnel data.
    Schlagwort(e): AERODYNAMICS
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 64; 21-37
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  • 30
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    Some effects of interference flowfields on supersonic configurations (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 880-885
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  • 31
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    Supersonic airfoil optimization (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 873-879
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  • 32
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    Algebraic grid generation about wing-fuselage bodies (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An algebraic procedure for generating boundary-fitted grids about wing-fuselage configurations is presented. A wing-fuselage configuration consists of two aircraft components specified by cross sections and mathematically represented by Coons' patches. Several grid blocks are constructed to cover the entire region surrounding the configuration, and each grid block maps into a computational cube. Grid points are first determined on the six boundary surfaces of a block and then in the interior. Grid points on the surface of the configuration are derived from the intersection of planes with the Coons' patch definition. Approximate arc length distributions along the resulting grid curves concentrate and disperse grid points. The two-boundary technique and transfinite interpolation are used to determine grid points on the remaining boundary surfaces and block interiors.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 868-872
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  • 33
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    Planform effects for low-fineness-ratio multibody configurations at supersonic speeds (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 856-860
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  • 34
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    30-micron heterodyne receiver (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Advantages and constraints of remote measurements using heterodyne spectroscopy near 30 microns are discussed. The state of the art of wideband HgCdTe photomixers and PbSnSe diode-laser local oscillators being developed for FIR heterodyne receivers is described. The first compact 30-micron heterodyne radiometer was built, and initial results at 28-microns show about 2-percent mixer efficiency for a 500-MHz-bandwidth receiver. Factors limiting receiver performance are discussed, along with the projected sensitivity of new interdigitated-electrode HgCdTe photoconductor mixers being developed for operation up to 200 microns.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: International Journal of Infrared and Millimeter Waves (ISSN 0195-9271); 8; 1269-127
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  • 35
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    Improved finite-difference schemes for transonic potential flow calculations (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 1456-146
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  • 36
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    Vortex simulation of forced/unforced mixing layers (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: AIAA Journal (ISSN 0001-1452); 25; 1417
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  • 37
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    Multispecies coherent anti-Stokes Raman scattering instrument for turbulent combustion (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A nonintrusive diagnostic system is described which permits simultaneous measurement of temperature, nitrogen number density, and oxygen number density in hostile combustion environments. This system is pumped by a 10-Hz neodymium YAG laser, and signals are detected with an intensified photodiode array and dual photomultipliers. The system utilizes a folded BOXCARS beam arrangement, two probe dye lasers, dynamic range expansion, polarization rejection of nonresonant background, and multiplexing of the signal beams.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Review of Scientific Instruments (ISSN 0034-6748); 58; 2075-208
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  • 38
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    Image processing by four-wave mixing in photorefractive GaAs (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Three image processing experiments were performed by degenerate four-wave mixing in photorefractive GaAs. The experiments were imaging by phase conjugation, edge enhancement, and autocorrelation. The results show that undoped, semiinsulating, liquid-encapsulated Czochralski-grown GaAs crystals can be used as effective optical processing media despite their small electrooptic coefficient.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Physics Letters (ISSN 0003-6951); 51; 1481-148
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  • 39
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    Computed and experimental surface pressure and heating on 70-deg sphere cones (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 385-393
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  • 40
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    Transition on swept leading edges at Mach 3.5 (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 710-717
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  • 41
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    Aerodynamic effects of distributed spanwise blowing on a fighter configuration (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 673-679
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  • 42
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    Airborne tracking sunphotometer (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An airborne tracking sunphotometer, mounted on the outside top surface of an aircaft has been developed to provide unresricted viewing of the sun. This instrument will substantially increase the data that scientists can gather for atmospheric studies. The instrument has six wavelength channels and an automatic data gathering system. The instrument's optical features, tracking capability, mechanical features, and data gathering system are described.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 4; 336-339
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  • 43
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    Report of the Special Panel on statistical particle bias problems in laser anemometry (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An account is given of the findings contained in a concensus document compiled by a group of experts on laser anemometry concerning statistical particle bias and its possible remedies. Emphasis is placed on the systematic character of this bias, rather than its magnitude. Since bias errors are a function of flow velocity and turbulence intensity, the measured results may contain apparent trends due solely to the measurement process. Attention is given to the panel's attempt to clear up terminological confusions in the matter of rates, scales, and magnitudes, as well as to its suggested processing methods for the elimination of velocity bias and the remedy of angle bias.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: ASME, Transactions, Journal of Fluids Engineering (ISSN 0098-2202); 109; 89-93
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  • 44
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    In situ ozone instrumentation for 10-Hz measurements - Development and evaluation (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The development of the fast-response ozone detector for the Electra aircraft is described. The selection of a technique to meet the design goal of 10-Hz detection is examined in terms of detection principles, instrument sampling parameters, signal conditioning, and aircraft and sampling environment. An instrument which employs a NO technique for detection of ozone with a reaction chamber volume of 16 cu cm, a pressure of 60 torr, and a sample flow of 1000 standard cu cm/min was developed. Laboratory and flight testings of the detector were conducted in order to evaluate its performance. The data reveal that the fast-response ozone detector is highly reliable with a response of 0.1 sec to 90 percent of reading, has a lower detection limit of 1 ppbv, and an S/N of 20 at 20 ppbv ozone.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 45
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    Moire interferometry, 1986 (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Current capabilities of moire interferometry are described. Several examples illustrate this whole-field optical technique for measurements of in-plane displacements. Sensitivity corresponds to moire measurements with gratings of 2400 lines/mm. The examples are taken from studies of composite members, material anomalies, plasticity, joints, micromechanics and strain concentrations. The abundance of high-sensitivity displacement information permits calculation of normal strains and shear strains in the field, including critical zones of very high gradients.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 46
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    Bifurcations in unsteady aerodynamics (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Nonlinear algebraic functional expansions are used to create a form for the unsteady aerodynamic response that is consistent with solutions of the time dependent Navier-Stokes equations. An enumeration of means of invalidating Frechet differentiability of the aerodynamic response, one of which is aerodynamic bifurcation, is proposed as a way of classifying steady and unsteady aerodynamic phenomena that are important in flight dynamics applications. Accommodating bifurcation phenomena involving time dependent equilibrium states within a mathematical model of the aerodynamic response raises an issue of memory effects that becomes more important with each successive bifurcation.
    Schlagwort(e): AERODYNAMICS
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  • 47
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    Wave-measurement capabilities of the surface contour radar and the airborne oceanographic lidar (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The 36-gigahertz surface contour radar and the airborne oceanographic lidar were used in the SIR-B underflight mission off the coast of Chile in October 1984. The two systems and some of their wave-measurement capabilities are described. The surface contour radar can determine the directional wave spectrum and eliminate the 180-degree ambiguity in wave propagation direction that is inherent in some other techniques such as stereophotography and the radar ocean wave spectrometer. The Airborne Oceanographic Lidar can acquire profile data on the waves and produce a spectrum that is close to the nondirectional ocean-wave spectrum for ground tracks parallel to the wave propagation direction.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Johns Hopkins APL Technical Digest (ISSN 0270-5214); 8; 74-81
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  • 48
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    An anemometer for highly turbulent or recirculating flows (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An anemometer which determines flow velocity by ionizing air and sensing the convective displacement of the ions is described. It is suited to measurement in low speed, highly unsteady gas flows. Comparisons to hot wire spectra suggest the corona anemometer has adequate frequency response to make it a useful tool for fluid dynamics measurement.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Experiments in Fluids (ISSN 0723-4864); 5; 3, 19
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  • 49
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    Computer graphic visualization of Orbiter lower surface boundary-layer transition (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 109-114
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  • 50
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    Hypersonic aerodynamics for an entry research vehicle (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 97
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  • 51
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    Drag reduction on a bluff body at yaw angles to 30 degrees (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The base separation alleviation and drag reduction effectiveness of transverse rectangular grooves and longitudinal v-grooves in the afterbody shoulder region of a bluff body is investigated for body yaw angles of 0-30 deg. The grooves are found to be beneficial in reducing both freestream and axial drag coefficients at yaw angles of up to 25 deg.
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 179-181
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  • 52
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    High-speed aerodynamics of several blunt-cone configurations (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 127-132
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  • 53
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    Fast-response, high-precision carbon monoxide sensor using a tunable diode laser absorption technique (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A tunable diode laser instrument, denoted as DACOM (Differential Absorption CO Measurement), has been developed to meet the fast-response, high-precision CO measurement needs of the GTE (Global Tropospheric Experiment) program. Under the GTE program, DACOM participated in the three field missions of CITE 1 (Chemical Instrumentation Test and Evaluation 1), a project involving the intercomparison of trace gas measurement techniques. DACOM performance, including analyses of measurement error sources, is discussed for the ground-based mission at Wallops Island, VA (summer 1983), and two missions on the NASA CV-990 (fall 1983 and spring 1984). Examples of fast-response (about 1 s), high-precision (+ or - 1 part per billion by volume, + or - 1.5 percent of reading) airborne data are included to illustrate the capability of this instrument.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 92; 2071-208
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  • 54
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    Induced-drag characteristics of crescent-moon-shaped wings (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 115-119
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  • 55
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    Loss-compensation technique for fiber-optic sensors and its application to displacement measurements (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This report describes a new type of intensity-modulating fiber-optic sensor which has high immunity to the effects of variations in the losses of the fiber-link. A variable-splitting-ratio transducer is used to differentially modulate the intensities of the light which it transmits and reflects. Using a four-fiber optical link, light is impinged onto the transducer from either direction, and in each case, the transmitted and reflected signals are measured. These four signals are then processed to remove the effects of the fiber and connector losses. Loss-compensated sensors of angular position and displacement are described, and their outputs are shown to be highly stable despite considerable variations in the transmissivities of the fiber-link components.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics (ISSN 0003-6935); 26; 452-455
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  • 56
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    Fiber-optic photoelastic pressure sensor with fiber-loss compensation (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A new fiber-optic pressure sensor is described that has high immunity to the effects of fiber-loss variations. This device uses the photoelastic effect to modulate the proportion of the light from each of two input fibers that is coupled into each of two output fibers. This four-fiber link permits two detectors to be used to measure the sensor's responses to the light from each of two independently controlled sources. These four detector outputs are processed to yield a loss-compensated signal that is a stable and sensitive pressure indicator.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Optics Letters (ISSN 0146-9592); 12; 220-222
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  • 57
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    Measured unsteady transonic aerodynamic characteristics of an elastic supercritical wing (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 225-230
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  • 58
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    Unsteady aerodynamics of blade rows (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The requirements placed on an unsteady aerodynamic theory intended for turbomachinery aeroelastic applications are discussed along with a brief description of the various theoretical models that are available to address these requirements. The main emphasis is placed on the description of a linearized inviscid theory which fully accounts for the effects of a nonuniform mean or steady flow on unsteady aerodynamic response. Although this theory has been developed primarily for blade flutter prediction, more general equations are presented which account for unsteady excitations due to incident external aerodynamic disturbances as well as those due to blade motions. The resulting equations consist of a system of three field equations along with conditions imposed at blade, wake and shock surfaces and in the far field. These equations can be solved to determine the fluctuations in all fluid dynamic properties throughout the required solution domain. Example solutions are presented to demonstrate several effects associated with nonuniform steady flows on the linearized unsteady aerodynamic response to prescribed blade motions.
    Schlagwort(e): AERODYNAMICS
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  • 59
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    Shock-capturing technique for hypersonic, chemically relaxing flows (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 481-488
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  • 60
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    A simple device for the preparation of embedded materials science specimens for ultramicrotomy (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Electron Microscopy Technique (ISSN 0741-0581); 6; 305
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  • 61
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    Addressing the hypersonic simulation problem (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 334-341
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  • 62
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    Aerodynamic characteristics of biplanes with winglets (1987)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 24; 518-522
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    Spectral and radiometric calibration of the Airborne Visible/Infrared Imaging Spectrometer (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The laboratory spectral and radiometric calibration of the AVIRIS science data collected since 1987 is described. The instrumentation and procedures used in the calibration are discussed and the accuracy achieved in the laboratory as determined by measurement and calculation is compared with the requirements. Instrument performance factors affecting radiometry are described. The paper concludes with a discussion of future plans.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A Description of the Sensor, Ground Data Processing Facility, Laboratory Calibration, and First Results; Airborne Visible(Inf
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    AVIRIS scan drive design and performance (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) images the ground with an instantaneous field of view (IFOV) of 1 mrad. The IFOV is scanned 30 deg from left to right to provide the cross-track dimension of the image, while the aircraft's motion provides the along-track dimension. The scanning frequency is 12 Hz, with a scan efficiency of 70 percent. The scan mirror has an effective diameter of 5.7 in, and its positional accuracy is a small fraction of a milliradian of the nominal position-time profile. Described are the design and performance of the scan drive mechanism. Tradeoffs among various approaches are discussed, and the reasons given for the selection of the cam drive.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A Description of the Sensor, Ground Data Processing Facility, Laboratory Calibration, and First Results; Airborne Visible(Inf
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    Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) spectrometer design and performance (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The development of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has been completed at JPL. This paper outlines the functional requirements of the spectrometer optics subsystem, and describes the spectrometer optical design. The optical subsystem performance is shown in terms of spectral modulation transfer functions, radial energy distributions, and system transmission at selected wavelengths for the four spectrometers. An outline of the spectrometer alignment is included.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). A Description of the Sensor, Ground Data Processing Facility, Laboratory Calibration, and First Results; Airborne Visible(Inf
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    Particle field holography data reduction by Fourier transform analysis (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The size distribution of a particle field hologram is obtained with a Fourier transformation of the Fraunhofer diffraction pattern of the reconstructed hologram. Off-axis absorption holograms of particle fields with known characteristics were obtained and analyzed with a commercially available instrument. The mean particle size of the reconstructed hologram was measured with an error of + or - 5 percent, while the distribution broadening was estimated within + or - 15 percent. Small sections of a pulsed laser hologram of a synthetic fuel spray were analyzed with this method thus yielding a spatially resolved size distribution. The method yields fast and accurate automated analysis of particle field holograms.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA. Ames Research Center, Automated Reduction of Data from Images and Holograms; p 541-564
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    The Fringe Reading Facility at the Max-Planck-Institut fuer Stroemungsforschung (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A Mach-Zehnder interferometer is used for optical flow measurements in a transonic wind tunnel. Holographic interferograms are reconstructed by illumination with a He-Ne-laser and viewed by a video camera through wide angle optics. This setup was used for investigating industrial double exposure holograms of truck tires in order to develop methods of automatic recognition of certain manufacturing faults. Automatic input is achieved by a transient recorder digitizing the output of a TV camera and transferring the digitized data to a PDP11-34. Interest centered around sequences of interferograms showing the interaction of vortices with a profile and subsequent emission of sound generated by this process. The objective is the extraction of quantitative data which relates to the emission of noise.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA. Ames Research Center, Automated Reduction of Data from Images and Holograms; p 433-436
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  • 68
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    Information retrieval from holographic interferograms: Fundamentals and problems (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Holographic interferograms can contain large amounts of information about flow and temperature fields. Their information content can be very high because they can be viewed from many different directions. This multidirectionality, and fringe localization add to the information contained in the fringe pattern if diffuse illumination is used. Additional information, and increased accuracy can be obtained through the use of dual reference wave holography to add reference fringes or to effect discrete phase shift or hetrodyne interferometry. Automated analysis of fringes is possible if interferograms are of simple structure and good quality. However, in practice a large number of practical problems can arise, so that a difficult image processing task results.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA. Ames Research Center, Automated Reduction of Data from Images and Holograms; p 1-20
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  • 69
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    A method for using a time interval counter to measure frequency stability (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: It is shown how a commercial time interval counter can be used to measure the relative stability of two signals that are offset in frequency and mixed down to a beat note of about 1 Hz. To avoid the dead-time problem, the counter is set up to read the time interval between each beat note upcrossing and the next pulse of a 10 Hz reference pulse train. The actual upcrossing times are recovered by a simple algorithm whose outputs can be used for computing residuals and Allan variance. A noise floor-test yielded a delta f/f Allan deviation of 1.3 times 10 to the minus 9th power/tau relative to the beat frequency.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: The Telecommunications and Data Acquisition Report; p 149-156
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  • 70
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    CFD applications: The Lockheed perspective (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Numerical Aerodynamic Simulator (NAS) epitomizes the coming of age of supercomputing and opens exciting horizons in the world of numerical simulation. An overview of supercomputing at Lockheed Corporation in the area of Computational Fluid Dynamics (CFD) is presented. This overview will focus on developments and applications of CFD as an aircraft design tool and will attempt to present an assessment, withing this context, of the state-of-the-art in CFD methodology.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA. Ames Research Center, Supercomputing in Aerospace; p 77-85
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  • 71
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    A comparison of turbulence measurement methods (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: An experiment is described in which temperature (density) and velocity are measured separately but simultaneously as functions of time so that it is possible to determine the relationships among velocity, density, and the product of density and velocity. Temperatures were measured with a dual-wire thermocouple probe. Velocity data were supplied by a fringe laser-Doppler anemometer. Signals from thermocouples and the laser were recorded on FM magnetic tape for later processing.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Turbine Engine Hot Section Technology, 1987; p 81-84
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  • 72
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    Progress on a PdCr wire strain gage (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The principal activity under the HOST effort to improve the state of the art in high temperature static strain measurement has been a contract under which a palladium-chromium (PdCr) alloy was developed. The contract effort is continuing with the goal of developing a thin film high temperature static strain gage system. In addition to this effort, researchers contracted with Battelle-Columbus Laboratories to draw the PdCr allow into wire while researchers at Lewis worked to gain experience with this alloy as a wire strain gage.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Turbine Engine Hot Section Technology, 1987; p 77-79
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  • 73
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    Elevated temperature strain gages (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The objective is to study the electrical resistance of materials that are potentially useful as resistance strain gages at 1000 C. A set of criteria were set and used to select strain gage candidate materials that are electrically stable and reproducible at all temperatures up to 1000 C. For the experimental phase of this research, the electrical resistance change with temperature of three groups of materials (solid solution alloys, transition metal carbides, and semiconductors) were studied with the intention of identifying materials with low temperature coefficient of resistance and low resistance drift rate at 1000 C. A preliminary study of the gage factor on one of the best candidate materials, B sub 4 C, was also undertaken. The results of these investigations are presented.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: NASA, Lewis Research Center, Turbine Engine Hot Section Technology, 1987; p 53-75
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  • 74
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    The Radar Ocean-Wave Spectrometer (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The scanning-beam Radar Ocean-Wave Spectrometer (ROWS) technique is described. The derivation of a spectrum for the reflectivity modulation as a function of range is examined. The usefulness of the ROWS technique was initially validated using aircraft data obtained in 1978 with the GSFC Ku-band pulse-compression radar; additional examples of aircraft data which verify the effectiveness of the ROWS technique are presented. The development of a ROWS mode for Spectrasat is discussed. Consideration is given to the incidence angle, twin beam option for cross-section roll-off and wind vector determination, rotation rate, antenna and footprint dimensions, integration time, sphericity effects, and a processor configuration. A design for the ROWS-mode time-domain processor on Spectrasat is proposed. The performance of the system is evaluated, and it is determined that the system performs well.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Johns Hopkins APL Technical Digest (ISSN 0270-5214); 8; 116-127
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  • 75
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    Direct simulation of hypersonic flows over blunt wedges (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AERODYNAMICS
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 1; 97-104
    Format: text
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  • 76
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    Supersonic boundary-layer transition on the LaRC F-106 and the DFRF F-15 aircraft. Part 2: Aerodynamic predictions (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: In the leading edge region, the measured pressure distributions exhibit extreme variations from strong suction peaks to a pressure maximum at the attachment line. These variations occur over short distances on the wing surface, and their character changes with changes in Mach number and angle of attack. The data/theory comparisons show that the character of the measured pressure distributions is well predicted for every Mach number and/or angle of attack condition considered. There is good agreement between theory and experiment for the location of the attachment line and suction peaks. The pressure magnitudes are well represented in the critical leading edge region, including the pressure maximum on the attachment line. The wing/body/inlet results agree well with the wing alone back to about 20 percent of chord where the upper surface suction peak typically occurs. The largest differences between theory and measurement always occur in the vicinity of suction peaks, with the difference being approximately 15 percent or less. In regions of largest error, the predicted pressures underestimate the suction peak strength for each case considered. The ability of the NCOREL code to reproduce wing pressure characteristics is shown.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 1015-1024
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  • 77
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    Supersonic boundary-layer transition on the LaRC F-106 and the DFRF F-15 aircraft. Part 1: Transition measurements and stability analysis (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: For the case of the F-15 flight tests, boundary layer transition was observed up to Mach numbers of 1.2. For very limited and specific flight conditions, laminar flow existed back to about 20 percent chord on the surface clean up glove. Hot film instrumentation was effective for locating the region of transition. For the F-106 flight tests, transition on the wing or vertical tail generally occurred very near the attachment line. Transition was believed to be caused by either attachment line contamination or strong cross flow development due to the high sweep angles of the test articles. The compressibility analysis showed that cross flow N-factors were in the range of 5 to 12 at transition.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 997-1014
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  • 78
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    Experimental and theoretical investigation of boundary-layer instability mechanisms on a swept leading edge at Mach 3.5 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A brief outline of the experimental and theoretical investigation of boundary layer instability mechanisms on a swept leading edge at Mach 3.5 is presented. Transition is affected by wind tunnel noise only when roughness is present. Local bar-R sub * Reynolds number and k/eta sub * are useful correlation parameters for a wide range of free stream Mach numbers. Stability theory is in good agreement with the experimental cross flow vortex wavelength. These conclusions are briefly discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 981-995
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  • 79
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    The effects of wall surface defects on boundary-layer transition in quiet and noisy supersonic flow (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The design of supersonic vehicles with laminar flow control and vehicles such as the Space Shuttle requires information on allowable transition tolerances to fabrication defects such as discrete surface roughness and waviness. A relatively large data base on the effects of discrete roughness on transition exists for subsonic and supersonic speeds. The existing supersonic wind tunnel transition data are contaminated by wind tunnel noise emanating from the turbulent boundary layers on the nozzle walls. Roughness and waviness transition data obtained in a quiet Mach 3.5 supersonic wind tunnel are compared with those obtained in conventional noisy flows.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 965-980
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  • 80
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    Supersonic laminar-flow control (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Detailed, up to date systems studies of the application of laminar flow control (LFC) to various supersonic missions and/or vehicles, both civilian and military, are not yet available. However, various first order looks at the benefits are summarized. The bottom line is that laminar flow control may allow development of a viable second generation SST. This follows from a combination of reduced fuel, structure, and insulation weight permitting operation at higher altitudes, thereby lowering sonic boom along with improving performance. The long stage lengths associated with the emerging economic importance of the Pacific Basin are creating a serious and renewed requirement for such a vehicle. Supersonic LFC techniques are discussed.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 923-946
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  • 81
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    Experimental and numerical analyses of laminar boundary-layer flow stability over an aircraft fuselage forebody (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Fuelled by a need to reduce viscous drag of airframes, significant advances have been made in the last decade to design lifting surface geometries with considerable amounts of laminar flow. In contrast to the present understanding of practical limits for natural laminar flow over lifting surfaces, limited experimental results are available examining applicability of natural laminar flow over axisymmetric and nonaxisymmetric fuselage shapes at relevantly high length Reynolds numbers. The drag benefits attainable by realizing laminar flow over nonlifting aircraft components such as fuselages and nacelles are shown. A flight experiment to investigate transition location and transition mode over the forward fuselage of a light twin engine propeller driven airplane is examined.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 861-886
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  • 82
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    Wind tunnel results of the high-speed NLF(1)-0213 airfoil (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Wind tunnel tests were conducted to evaluate a natural laminar flow airfoil designed for the high speed jet aircraft in general aviation. The airfoil, designated as the High Speed Natural Laminar Flow (HSNLF)(1)-0213, was tested in two dimensional wind tunnels to investigate the performance of the basic airfoil shape. A three dimensional wing designed with this airfoil and a high lift flap system is also being evaluated with a full size, half span model.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 697-726
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  • 83
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    Design and test of a natural laminar flow/large Reynolds number airfoil with a high design cruise lift coefficient (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Research activity on an airfoil designed for a large airplane capable of very long endurance times at a low Mach number of 0.22 is examined. Airplane mission objectives and design optimization resulted in requirements for a very high design lift coefficient and a large amount of laminar flow at high Reynolds number to increase the lift/drag ratio and reduce the loiter lift coefficient. Natural laminar flow was selected instead of distributed mechanical suction for the measurement technique. A design lift coefficient of 1.5 was identified as the highest which could be achieved with a large extent of laminar flow. A single element airfoil was designed using an inverse boundary layer solution and inverse airfoil design computer codes to create an airfoil section that would achieve performance goals. The design process and results, including airfoil shape, pressure distributions, and aerodynamic characteristics are presented. A two dimensional wind tunnel model was constructed and tested in a NASA Low Turbulence Pressure Tunnel which enabled testing at full scale design Reynolds number. A comparison is made between theoretical and measured results to establish accuracy and quality of the airfoil design technique.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA, Langley Research Center, Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 727-751
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  • 84
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    Design of the low-speed NLF(1)-0414F and the high-speed HSNLF(1)-0213 airfoils with high-lift systems (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The design and testing of Natural Laminar Flow (NLF) airfoils is examined. The NLF airfoil was designed for low speed, having a low profile drag at high chord Reynolds numbers. The success of the low speed NLF airfoil sparked interest in a high speed NLF airfoil applied to a single engine business jet with an unswept wing. Work was also conducted on the two dimensional flap design. The airfoil was decambered by removing the aft loading, however, high design Mach numbers are possible by increasing the aft loading and reducing the camber overall on the airfoil. This approach would also allow for flatter acceleration regions which are more stabilizing for cross flow disturbances. Sweep could then be used to increase the design Mach number to a higher value also. There would be some degradation of high lift by decambering the airfoil overall, and this aspect would have to be considered in a final design.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 637-671
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  • 85
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    Wind tunnel results of the low-speed NLF(1)-0414F airfoil (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The large performance gains predicted for the Natural Laminar Flow (NLF)(1)-0414F airfoil were demonstrated in two-dimensional airfoil tests and in wind tunnel tests conducted with a full scale modified Cessna 210. The performance gains result from maintaining extensive areas of natural laminar flow, and were verified by flight tests conducted with the modified Cessna. The lift, stability, and control characteristics of the Cessna were found to be essentially unchanged when boundary layer transition was fixed near the wing leading edge. These characteristics are very desirable from a safety and certification view where premature boundary layer transition (due to insect contamination, etc.) must be considered. The leading edge modifications were found to enhance the roll damping of the Cessna at the stall, and were therefore considered effective in improving the stall/departure resistance. Also, the modifications were found to be responsible for only minor performance penalties.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 3; p 673-696
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  • 86
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    Numerical experiments on transition control in wall-bounded shear flows (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Results are presented from a numerical simulation of transition control in plane channel and boundary layer flows. The analysis is based on a pseudo-spectral/finite difference semi-implicit solution procedure employed to numerically integrate the time-dependent, three-dimensional, incompressible Navier-Stokes equations in a doubly periodic domain. In the channel flow, it was found that the active periodic suction/blowing method was effective in controlling strongly three-dimensional disturbances. In the boundary layer, the preliminary analysis indicated that in the early stages, passive control by suction is as effective as active control to suppress instabilities. The current work is focused on a detailed comparison of active and passive control by suction/blowing in the boundary layer.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA, Langley Research Center, Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 577-592
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  • 87
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    Application of sound and temperature to control boundary-layer transition (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The growth and decay of a wave packet convecting in a boundary layer over a concave-convex surface and its active control by localized surface heating are studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiations are computed using linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. It is shown that on the concave portion the amplitude of the wave packet increases and its bandwidth broadens while on the convex portion some of the components in the packet are stabilized. The pressure field decays exponentially away from the surface and then algebraically, exhibiting a decay characteristic of acoustic waves in two dimensions. The far-field acoustic behavior exhibits a super-directivity type of behavior with a beaming downstream. Active control by surface heating is shown to reduce the growth of the wave packet but have little effect on acoustic far field behavior for the cases considered. Active control by sound emanating from the surface of an airfoil in the vicinity of the leading edge is experimentally investigated. The purpose is to control the separated region at high angles of attack. The results show that injection of sound at shedding frequency of the flow is effective in an increase of lift and reduction of drag.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 593-616
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  • 88
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    Theoretical methods and design studies for NLF and HLFC swept wings at subsonic and supersonic speeds (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Laminarization of the boundary layer on the surface of aircraft wings can be accomplished by the use of concepts such as Natural Laminar Flow (NLF), Laminar-Flow Control (LFC), and Hybrid Laminar-Flow Control (HLFC). Several integral boundary-layer methods were developed for the prediction of laminar, transition, and separating turbulent boundary layers. These methods were developed for use at either subsonic or supersonic speeds, have small computer execution times, and are simple to use. The theoretical equations and assumptions which form the basis of the boundary-layer method, are briefly outlined and the results of several correlation cases with exciting experimental data are presented.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 547-575
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  • 89
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    Numerical solutions of the compressible 3-D boundary-layer equations for aerospace configurations with emphasis on LFC (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The application of stability theory in Laminar Flow Control (LFC) research requires that density and velocity profiles be specified throughout the viscous flow field of interest. These profile values must be as numerically accurate as possible and free of any numerically induced oscillations. Guidelines for the present research project are presented: develop an efficient and accurate procedure for solving the 3-D boundary layer equation for aerospace configurations; develop an interface program to couple selected 3-D inviscid programs that span the subsonic to hypersonic Mach number range; and document and release software to the LFC community. The interface program was found to be a dependable approach for developing a user friendly procedure for generating the boundary-layer grid and transforming an inviscid solution from a relatively coarse grid to a sufficiently fine boundary-layer grid. The boundary-layer program was shown to be fourth-order accurate in the direction normal to the wall boundary and second-order accurate in planes parallel to the boundary. The fourth-order accuracy allows accurate calculations with as few as one-fifth the number of grid points required for conventional second-order schemes.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 517-545
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  • 90
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    Sensitivity of LFC techniques in the non-linear regime (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: For all the Laminar Flow Control (LFC) techniques examined, finite-amplitude effects are destabilizing, i.e., finite-amplitude 2-D Tollmien-Schlichting (TS) waves grow faster than predicted by linear theory. It was also found, in direct contrast to the results from linear theory for low-amplitude waves, that temperature fluctuations exert a further destabilizing influence on finite amplitude 2-D TS waves. The controlled boundary layers are, of course, subject to intense 3-D secondary instabilities. The instantaneous growth rates of both the fundamental and subharmonic instabilities are strongly tied to the amplitude of the primary 2-D wave. The principal finite-amplitude effects upon the 3-D secondary instabilities occur through the faster growth of the 2-D waves.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 491-516
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  • 91
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    Boundary-layer stability analysis of Langley Research Center 8-foot LFC experimental data (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: An analytical study of linear-amplifying instabilities of a laminar boundary layer as found in the experimental data of the LaRC/8-foot laminar-flow control (LFC) experiment was completed and the results are presented. The LFC airfoil used for this experiment was a swept, supercritical design which removed suction air through spanwise slots. The amplification of small disturbances by linear processes on a swept surface such as this can be due to either Tollmien-Schlichting (TS) and/or crossflow (CF) mechanisms. This study consists of the examination of these two instabilities by both the commonly used incompressible (SALLY and MARIA) analysis and the more involved compressible (COSAL) analysis. A wide range of experimental test conditions with variations in Mach number, Reynolds number, and suction distributions were available for this study. Experimentally determined transition locations were found from thin-film techniques and were used to correlate the n-factors at transition for the range of test cases.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 471-489
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  • 92
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    An experimental evaluation of slots versus porous strips for laminar-flow applications (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Detailed mean velocity and disturbance amplitude measurements were conducted in a Blasius boundary-layer flow with wall suction applied at three downstream locations. The main emphasis was a direct comparison of the growth rate of the instability wave with discrete spanwise slots versus wide porous strips. The results demonstrate that the local effects of suction through slots or very narrow porous strips have a greater beneficial effect on the stability of the boundary-layer flow relative to the suction influence of a wide porous strip. Codes which use continuous suction for the growth rates of the instability waves to determine the suction quantities for a multiple series of slots will be quite conservative in the estimation of the suction quantity. Guidelines were provided for suction-chamber design and flow rates to minimize internal oscillations which propagate into the boundary-layer flow.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA, Langley Research Center, Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 435-451
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    Results of LFC experiment on slotted swept supercritical airfoil in Langley's 8-foot transonic pressure tunnel (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A large chord swept supercritical laminar-flow control (LFC) airfoil was designed, constructed, and tested in the Langley 8-foot Transonic Pressure Tunnel (TPT). The LFC airfoil experiment was established to provide basic information concerning the design and compatibility of high performance supercritical airfoils with suction boundary-layer control achieved through fine slots or porous surface concepts. Shockless pressure distribution was achieved. Full chord laminar flow was achieved on upper and lower surfaces. Full chord laminar flow was maintained at subcritical speeds and over large supercritical zones. Feasibility of combined suction laminarization and supercritical airfoil technology was demonstrated.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 453-469
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  • 94
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    Experimental studies on Goertler vortices (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Goertler vortices arise in laminar boundary layers along concave walls due to an imbalance between pressure and centrifugal forces. In advanced laminar-flow control (LFC) supercritical airfoil designs, boundary-layer suction is primarily used to control Tollmien-Schlichting instability and cross-flow vortices in the concave region near the leading edge of the airfoil lower surface. The concave region itself is comprised of a number of linear segments positioned to limit the total growth of Goertler vortices. Such an approach is based on physical reasonings but rigorous theoretical justification or experimental evidence to support such an approach does not exist. An experimental project was initiated at NASA Langley to verify this concept. In the first phase of the project an experiment was conducted on an airfoil whose concave region has a continuous curvature distribution. Some results of this experiment were previously reported and significant features are summarized.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 421-433
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  • 95
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    Recent tests at Langley with a University of Tennessee Space Institute (UTSI) skin friction balance (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The experience at LaRC with the University of Tennessee Space Institute skin friction balances is summarized. The Karman-Schoenherr flat plate skin friction formulation is included for comparison. It is concluded that the balance is capable of operation in environments as diverse as cryogenic, transonic, high-shear rate of the 0.3 meter Transonic Cryogenic Tunnel, and high-temperature supersonic environment of the Unitary Plan Wind Tunnel. Proposed new research is outlined.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 407-411
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    Standort Signatur Erwartet Verfügbarkeit
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  • 96
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    Predicted and hot-film measured Tollmien-Schlichting wave characteristics (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Tollmien-Schlichting (TS) instability is a time-dependence instability which can lead to transition of laminar boundary layers on airfoils. A comparison of theoretical predictions and experimental observations of the TS instability on the NLF(1)-0414F airfoil designed by Viken and Pfenninger. The theoretical predictions were obtained using the SALLY stability code. Test results, from the same hot films that were used to detect transition, revealed that TS waves could be detected by the hot films if the hot-film signal was adequately modified.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 377-380
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  • 97
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    Flow quality measurements in compressible subsonic flows (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The purpose is to re-examine the heat transfer from a hot-wire probe in the compressible subsonic flow regime; describe the three-wire hot-wire probe calibration and data reduction techniques used to measure the velocity, density, and total temperature fluctuation; and present flow quality results obtained in the Langley 0.3 meter Transonic Cryogenic Wind Tunnel and in flight with the NASA JetStar from the same three-wire hot-wire probe.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 345-357
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  • 98
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    Effect of roughness on the stability of boundary layers (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: An analysis is conducted on the effect of imperfections consisting of humps and dips on the stability of incompressible flows over flat plates. The mean flow is calculated using interacting boundary layers. Linear quasiparallel spatial stability is used to calculate the growth rates and mode shapes of two-dimensional disturbances. Then, the amplification factor is computed. A search for the most dangerous frequency is conducted based on an amplification factor of 9 in the shortest distance. Correlations are made with the transition experiment of Walker and Greening using the e sup 9 method.
    Schlagwort(e): AERODYNAMICS
    Materialart: NASA, Langley Research Center, Research in Natural Laminar Flow and Laminar-Flow Control, Part 1; p 301-315
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  • 99
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    Advanced measurement techniques, part 1 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: 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.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 2; p 317-340
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  • 100
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    Goertler instability on an airfoil (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: An effective computational scheme was developed to study the growth/damping of Goertler vortices along walls of variable curvature. Computational experiments indicate that when the amplification rates for the u-, v-, and w-perturbations are the same, the finite difference approach to solve the initial value problem and the normal mode approach give identical results for the Blasius boundary layer on constant curvature concave walls. The growth of Goertler vortices was rapid in the concave regions and was followed by sharp damping in the convex region. However, multiple sets of counter-rotating vortices were formed and remained far downstream in the convex region. The current computational scheme can be easily extended to more realistic problems including variable pressure gradients and suction effects.
    Schlagwort(e): AERODYNAMICS
    Materialart: Research in Natural Laminar Flow and Laminar-Flow Control, Part 1; p 289-300
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    Standort Signatur Erwartet Verfügbarkeit
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