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  • AERODYNAMICS  (940)
  • AIRCRAFT PROPULSION AND POWER
  • Lunar and Planetary Science and Exploration
  • Meteorology and Climatology
  • 1985-1989  (582)
  • 1975-1979  (748)
  • 1950-1954  (1)
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  • 1
    Publication Date: 2016-06-07
    Description: Automated instruments were installed on a commercial B-747 aircraft, during the program, to obtain baseline data and to monitor key atmospheric constituents associated with emissions of aircraft engines in order to determine if aircraft are contributing to pollution of the upper atmosphere. Data thus acquired on a global basis over the commercial air routes for 5 to 10 years will be analyzed. Ozone measurements in the 29,000 to 45,000 foot altitude were expanded over what has been available from ozonesondes. Limited aerosol composition measurements from filter samples show low levels of sulfates and nitrates in the upper troposphere. Recently installed instruments for measurement of carbon monoxide and condensation nuclei are beginning to return data.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aircraft Eng. Emissions; p 323-355
    Format: application/pdf
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  • 2
    Publication Date: 2016-06-07
    Description: The status of an investigation of four numerical techniques for the time-dependent compressible Navier-Stokes equations is presented. Results for free shear layer calculations in the Reynolds number range from 1000 to 81000 indicate that a sequential alternating-direction implicit (ADI) finite-difference procedure requires longer computing times to reach steady state than a low-storage hopscotch finite-difference procedure. A finite-element method with cubic approximating functions was found to require excessive computer storage and computation times. A fourth method, an alternating-direction cubic spline technique which is still being tested, is also described.
    Keywords: AERODYNAMICS
    Type: Aerodynamic Analyses Requiring Advanced Computers, Pt. 1; p 437-468
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  • 3
    Publication Date: 2017-10-02
    Description: As a further demonstration of the capabilities of laser velocity in compressible aerodynamics, measurements obtained in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. In the separated-flow study, the comparisons were made against pitot-static pressure data. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. The laser data obtained in regions of extremely high turbulence suggest that velocity biasing does not occur if the particle occurrence rate is low relative to the turbulent fluctuation rate. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord MACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. Dual scatter optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations. Half-micron-diameter polystyrene spheres and naturally occurring condensed oil vapor acted as light scatterers in the two respective flows. Bragg-cell frequency shifting was utilized in the separated flow study.
    Keywords: AERODYNAMICS
    Type: AGARD Appl. of Non-Intrusive Instr. in Fluid Flow Res.; 12 p
    Format: text
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  • 4
    Publication Date: 2019-06-28
    Description: Experimental and empirical model results are presented that extend previous studies of the mixing of single-sided and opposed rows of jets in a confined duct flow to include effects of non-circular orifices and double rows of jets. Analysis of the mean temperature data obtained in this investigation showed that the effects of orifice shape and double rows are significant only in the region close to the injection plane, provided that the orifices are symmetric with respect to the main flow direction. The penetration and mixing of jets from 45-degree slanted slots is slightly less than that from equivalent-area symmetric orifices. The penetration from two-dimensional slots is similar to that from equivalent-area closely-spaced rows of holes, but the mixing is slower for the 2-D slots. Calculated mean temperature profiles downstream of jets from non-circular and double rows of orifices, made using an extension developed for a previous empirical model, are shown to be in good agreement with the measured distributions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-1104
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  • 5
    Publication Date: 2019-06-27
    Description: A single stage compressor was designed with the intent of demonstrating that, for a tip speed and hub-tip ratio typical of an advanced core compressor front stage, the use of low aspect ratio can permit high levels of blade loading to be achieved at an acceptable level of efficiency. The design pressure ratio is 1.8 at an adiabatic efficiency of 88.5 percent. Both rotor and stator have multiple-circular-arc airfoil sections. Variable IGV and stator vanes permit low speed matching adjustments. The design incorporates an inlet duct representative of an engine transition duct between fan and high pressure compressor.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159555 , PWA-5583-25
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  • 6
    Publication Date: 2019-07-13
    Description: The results of a program of experimental and analytical research in casing treatments over axial compressor rotor blade tips are presented. Circumferential groove, axial-skewed slot and blade angle slot treatments were tested at low speeds. With the circumferential groove treatment the stalling flow was reduced 5.8% at negligible efficiency sacrifice. The axial-skewed slot treatment improved the stalling flow by 15.3%; 1.8 points in peak efficiency were sacrificed. The blade angle slot treatment improved the stalling flow by 15.0%; 1.4 points in peak efficiency were sacrificed. The favorable stalling flow situations correlated well with observations of higher-than-normal surface pressures on the rotor blade pressure surfaces in the tip region, and with increased maximum diffusions on the suction surfaces. Annulus wall pressure gradients, especially in the 50 to 75% chord region, are also increased and blade surface pressure loadings are shifted toward the trailing edge for treated configurations.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 75-GT-60 , American Society of Mechanical Engineers, Gas Turbine Conference and Products Show; Mar 02, 1975 - Mar 06, 1975; Houston, TX
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  • 7
    Publication Date: 2019-07-13
    Description: The buffet prediction method uses rigid wind tunnel model fluctuating pressure data to form a buffet forcing function. The response is then calculated with a mathematical dynamic model of the airplane developed for gust response analysis. By including the extremes of phasing and contribution of symmetric and antisymmetric airplane responses, the upper and lower bounds are established for buffet response. F-111A flight test data show good agreement with predicted bounds for a variety of flight conditions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 75-69 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 20, 1975 - Jan 22, 1975; Pasadena, CA
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  • 8
    Publication Date: 2019-07-13
    Description: Results of experimental investigations into turbulent boundary-layer behavior under the influence of pressure gradients and with separation are presented for transonic and supersonic flow fields. In the transonic case, an axisymmetric model was implemented consisting of an annular circular arc bump affixed to a circular cylinder aligned with the flow direction. For the supersonic separation study, an oblique shock wave impinging on the wind tunnel wall boundary layer was employed to cause separation. The mean streamwise and normal velocity components as well as the respective turbulence intensities were obtained with a two-color frequency shifted laser velocimeter.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-47 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 9
    Publication Date: 2019-07-13
    Description: Experimental and empirical model results are presented that extend previous studies of the mixing of single-sided and opposed rows of jets in a confined duct flow to include effects of non-circular orifices and double rows of jets. Analysis of the mean temperature data obtained in this investigation showed that the effects of orifice shape and double rows are significant only in the region close to the injection plane, provided that the orifices are symmetric with respect to the main flow direction. The penetration and mixing of jets from 45-degree slanted slots is slightly less than that from equivalent-area symmetric orifices. The penetration from 2-dimensional slots is similar to that from equivalent-area closely-spaced rows of holes, but the mixing is slower for the 2-D slots. Calculated mean temperature profiles downstream of jets from non-circular and double rows of orifices, made using an extension developed for a previous empirical model, are shown to be in good agreement with the measured distributions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-86996 , E-2542 , NAS 1.15:86996 , Joint Propulsion Conf.; Jul 08, 1985 - Jul 10, 1985; Monterey, CA; United States
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  • 10
    Publication Date: 2006-07-16
    Description: Major solution techniques for internal computational fluid mechanics are discussed and some examples are presented. The major steps involved in developing a large computer code are then discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aeropropulsion 1979; p 187-230
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