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  • Other Sources  (5)
  • 1985-1989  (5)
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  • 1
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    Measurements of thermal ion energy spectra from the Giotto encounter with Comet Halley (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Ram ion measurements made by the Giotto neutral mass spectrometer show the spatial evolution of the composition and energy spectrum of coma ions. Near the nucleus the plasma is cold and has many constituents, but at distances of the order of 200,000 km the main ions are the terminal products of water dissociation, H(+) and O(+). The ion velocity distribution at the time of the Giotto encounter is highly anisotropic. Ion flow is generally away from the comet with energies increasing with distance to the order of 100 eV in the comet frame of reference. Similarities in the proton and oxygen ion energy spectra in the comet frame suggest an acceleration mechanism other than v x B pickup.
    Keywords: ASTROPHYSICS
    Type: ESA, Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 3: Posters 415-417 (SEE N87-26714 20-90); ESA, Proceedings of
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  • 2
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    On the CO and N2 abundance in Comet Halley (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The mass 28 amu/e signal observed in the neutral mode of the Giotto neutral gas mass spectrometer (NMS) is evaluated. At 1000 km from the nucleus number density n(CO)/ n(H2O) is less than or = 0.07. The production rate of CO as a parent molecule directly from the nucleus is thus less than 7% of the H2O production rate. However, CO is also produced from an extended source in the inner coma (r is less than 20,000 km) and at 20,000 km from the nucleus, for the total equivalent CO production rate 0.05 is less than or = Q(CO)/Q(H2O) is less than or = 0.15. For N2 an upper limit Q(N2)/Q(H2O) is less than or = 0.1 is derived. No parent molecule for the CO is identified in agreement with the NMS measurements. It is proposed that CO or a very short-lived parent is released in the coma from cometary dust grains, such as the CHON particles.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 383-386
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  • 3
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    The influence of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-177520 , NAS 1.26:177520
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  • 4
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    Effects of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3757 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 5
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    Flow direction measurement criteria and techniques planned for the 40- by 80-/80- x 120-foot wind tunnel integrated systems tests (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A study was performed in order to develop the criteria for the selection of flow direction indicators for use in the Integrated Systems Tests (ISTs) of the 40 by 80/80 by 120 Foot Wind Tunnel System. The problems, requirements, and limitations of flow direction measurement in the wind tunnel were investigated. The locations and types of flow direction measurements planned in the facility were discussed. A review of current methods of flow direction measurement was made and the most suitable technique for each location was chosen. A flow direction vane for each location was chosen. A flow direction vane that employs a Hall Effect Transducer was then developed and evaluated for application during the ISTs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176969 , NAS 1.26:176969
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