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  • CHEMISTRY  (3)
  • THERMODYNAMICS AND COMBUSTION  (1)
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  • 1
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    A preliminary sensitivity analysis of the coupled diffusion and chemistry model (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The sensitivity of the coupled chemistry/diffusion model's outputs to a wide range of variation of the model's independent variables has been investigated. It is shown that the efficiency with which the now catalytic cycle destroys ambient O3 is extremely sensitive to the amount of NO emitted and to the relative rates of turbulent diffusion and chemical reactions. For representative conditions in the stratosphere, a tenfold variation of either the turbulence intensity or the reaction rate constant or the source strength can vary the efficiency from 1% to 50%. If the duration of Phase 3 is a significant fraction of the total residence time of the plume, then these efficiency variations can alter O3 depletion rates by more than a factor of two. These results, therefore, point toward those variables which must be accurately defined or measured if one is to adequately predict the effect of SST operations on the ambient inventory of O3 in the lower stratosphere.
    Keywords: CHEMISTRY
    Type: NASA-CR-132369 , ARAP-203
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Some analyses of the chemistry and diffusion of SST exhaust materials during phase 3 of the wake period (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In the generally stably stratified lower stratosphere, SST exhaust plumes could spend a significant length of time in a relatively undispersed state. This effort has utilized invariant modeling techniques to simulate the separate and combined effects of atmospheric turbulence, turbulent diffusion, and chemical reactions of SST exhaust materials in the lower stratosphere. The primary results to date are: (1) The combination of relatively slow diffusive mixing and rapid chemical reactions during the Phase III wake period minimizes the effect of SST exhausts on O3 depletion by the so-called NOx catalytic cycle. While the SST-produced NO is substantially above background concentrations, it appears diffusive mixing of NO and O3 is simply too slow to produce the O3 depletions originally proposed. (2) The time required to dilute the SST exhaust plume may be a significant fraction of the total time these materials are resident in the lower stratosphere. If this is the case, then prior estimates of the environmental impact of these materials must be revised significantly downward.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-132323 , ARAP-199
    Format: application/pdf
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  • 3
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    The development and preliminary application of an invariant coupled diffusion and chemistry model (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In many real-world pollution chemical reaction problems, the rate of reaction problems, the rate of reaction may be greatly affected by unmixedness. An approximate closure scheme for a chemical kinetic submodel which conforms to the principles of invariant modeling and which accounts for the effects of inhomogeneous mixing over a wide range of conditions has been developed. This submodel has been coupled successfully with invariant turbulence and diffusion models, permitting calculation of two-dimensional diffusion of two reacting (isothermally) chemical species. The initial calculations indicate the ozone reactions in the wake of stratospheric aircraft will be substantially affected by the rate of diffusion of ozone into the wake, and in the early wake, by unmixedness.
    Keywords: CHEMISTRY
    Type: NASA-CR-2295 , REPT-193
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  • 4
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    Solutions of the chemical kinetic equations for initially inhomogeneous mixtures. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Following the recent discussions by O'Brien (1971) and Donaldson and Hilst (1972) of the effects of inhomogeneous mixing and turbulent diffusion on simple chemical reaction rates, the present report provides a more extensive analysis of when inhomogeneous mixing has a significant effect on chemical reaction rates. The analysis is then extended to the development of an approximate chemical sub-model which provides much improved predictions of chemical reaction rates over a wide range of inhomogeneities and pathological distributions of the concentrations of the reacting chemical species. In particular, the development of an approximate representation of the third-order correlations of the joint concentration fluctuations permits closure of the chemical sub-model at the level of the second-order moments of these fluctuations and the mean concentrations.
    Keywords: CHEMISTRY
    Type: AIAA PAPER 73-101 , Aerospace Sciences Meeting; Jan 10, 1973 - Jan 12, 1973; Washington, DC
    Format: text
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