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  • GEOPHYSICS  (1.929)
  • FLUID MECHANICS AND HEAT TRANSFER  (724)
  • SPACECRAFT DESIGN, TESTING AND PERFORMANCE
  • 1985-1989  (1.404)
  • 1980-1984  (1.051)
  • 1975-1979  (804)
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  • 1
    Publikationsdatum: 2013-08-31
    Beschreibung: A brief overview of flow separation phenomena is provided. Langley has many active research programs in flow separation related areas. Three cases are presented which describe specific examples of flow separation research. In each example, a description of the fundamental fluid physics and the complexity of the flow field is presented along with a method of either reducing or controlling the extent of separation. The following examples are discussed: flow over a smooth surface with an adverse pressure gradient; flow over a surface with a geometric discontinuity; and flow with shock-boundary layer interactions. These results will show that improvements are being made in the understanding of flow separation and its control.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Langley Symposium on Aerodynamics, Volume 1; p 361-374
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2011-08-19
    Beschreibung: Fluid dynamic aspects of the Antarctic ozone hole phenomena are studied. Data collected by the ER-2 aircraft as part of the Airborne Antarctic Ozone Experiment (AAOE) are used to calculate the potential vorticity distribution on potential temperature surfaces. Most of the ER-2 flights show a monotonic decrease in potential vorticity and nitrous oxide toward the pole on isentropic surfaces.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 94; 11625-11
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2011-08-18
    Beschreibung: The dynamics of the polar thermosphere are examined by using observations made from the Dynamics Explorer 2 satellite. The results used in this study were obtained primarily from the Fabry-Perot interferometer (FPI) and the wind and temperature spectrometer (WATS) during the time period from September 1981 through January 1982. Two primary geophysical conditions were examined: these were the southern summer and the northern winter polar regions. The results support the conclusion that above 60 degrees of latitude the neutral winds are strongly controlled by ion/neutral frictional momentum transfer resulting from magnetospheric convection. This implies that the natural coordinate system within which to display the neutral winds in the high polar thermosphere is magnetic. The collected observations of this study were used to assess the validity of two of the large thermospheric general circulation models. The result of this assessment was that the models reasonably represent the vector winds at high altitudes but do not, at present, accurately simulate the thermodynamics of that regime.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 5597-561
    Format: text
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  • 4
    Publikationsdatum: 2011-08-18
    Beschreibung: Four successive thermite barium releases at an altitude of 965 km over polar cap invariant latitudes 84 to 76 deg near magnetic midnight were conducted from the orbiting second stage of the vehicle that launched Nimbus 7; the releases were made as part of the CAMEO (Chemically Active Material Ejected in Orbit) program. This was the first opportunity to observe the behavior of conventional barium release when conducted at orbital velocity in the near-earth magnetic field. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba(+) expansion velocity relative to an expected velocity of 0.9 km/s. Attention is also given to neutral cloud expansion, initial ion cloud expansion, convective motion, and the characteristics of field-aligned motion. The possibility of measuring parallel electric fields over the polar cap by observing perturbations in the motion of the visible ions is assessed.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research; 86; May 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2011-08-17
    Beschreibung: Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Computers and Fluids; 6; June 197
    Format: text
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  • 6
    Publikationsdatum: 2011-08-17
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research; 84; Nov. 20
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2011-08-18
    Beschreibung: The LIMS experiment was launched on the Nimbus 7 satellite for the purpose of sounding the vertical structure of temperature and key upper atmosphere trace gases on a global scale. The technique of thermal infrared limb sounding was used to obtain measurements of O3, H2O, NO2, and HNO3. LIMS collected data almost continuously from late October to late May over the latitude range from 64 deg S to 84 deg N. Two of the gases, NO2 and HNO3, are important elements in the NO(x) chain of chemical reactions leading to ozone destruction. Results for these gases are described in terms of zonal mean profiles and latitudinal distributions. The period selected for study is January-May 1979, when a major stratospheric warming occurred.
    Schlagwort(e): GEOPHYSICS
    Materialart: (ISSN 0273-1177)
    Format: text
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  • 8
    Publikationsdatum: 2011-08-18
    Beschreibung: The LIMS experiment sounded the upper atmosphere from late October 1978 to late May 1979 and provided vertical profiles of atmospheric temperature, 03, H2O, HNO3, and NO2. Radiance averaging was used before retrieval to measure the altitude distribution of NO2 over the altitude range from the lower stratosphere into the mesosphere. Observations in the polar winter night region northward of about 70 deg N reveal NO2 levels near 175 ppbv at about 70 km, and they show a significant longitudinal variability (factor of 4 to 7). A definite temporal trend exists, showing a buildup of mesospheric and stratospheric NO2 during the polar night and a subsequent slowing of the increase of decline after sunlight returns, depending on altitude. The data represent the first experimental evidence that the thermosphere is an NO(x) source for the mesosphere and stratosphere.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 7267-727
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2011-08-18
    Beschreibung: Approximately seven and one half months of stratospheric ozone profiles have been processed from the LIMS (Limb Infrared Monitor of the Stratosphere) experiment on the Nimbus 7 satellite. Data profiles cover the stratosphere and mesosphere from 100 to 0.1 mbar and from 84 degrees N to 64 degrees S latitude. Topics covered include the ozone channel characteristics, precision, systematic uncertainties, and comparisons with data from balloon and rocket underflights, Umkehr soundings, and Dobson measurements. Comparisons with Dobson total ozone are made by integrating combined LIMS plus balloon profiles. The estimated on-orbit precision is 0.02-0.16 ppmv. Simulations of the experiment indicate potential systematic uncertainties ranging from 15 percent in the 1-mbar region to an upper limit of 40 percent at 100 mbar and 0.1 mbar. Results are well within the uncertainties for the correlative sensors themselves. LIMS detects significant vertical structure in the ozone profile even below the ozone mixing ratio peak. Several other comparisons showing good agreement are noted.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 5161-517
    Format: text
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  • 10
    Publikationsdatum: 2011-08-18
    Beschreibung: The Limb Infrared Monitor of the Stratosphere (LIMS) instrument on the Nimbus 7 spacecraft sensed limb emission profiles for 7 months, starting in October 1979. Vertical temperature profiles are inferred from measurements in two CO2 channels, and constituent profiles are obtained form the O3, HNO3, NO2, and water vapor channels. The line parameters used to calculate transmittances in the retrieval algorithm are presented. Their adequacy for LIMS and for other applications are assessed, and recommendations for future investigations are outlined.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 5141-514
    Format: text
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