Computer Science – Performance
Scientific paper
Sep 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001icar..153..180s&link_type=abstract
Icarus, Volume 153, Issue 1, pp. 180-196 (2001).
Computer Science
Performance
17
Scientific paper
The main aspect of this paper is to provide a synthesis between two major lines of development in the understanding of mass and heat transfer in a volatile porous medium. The first one is a macroscopic approach, where the medium is considered as a continuum, and heat and mass transfer equations are solved under appropriate boundary conditions for temperature and gas pressure (G. Steiner and N. I. Kömle 1991, Planet. Space Sci. 39, 507-513 Y. Mekler et al. 1990, Astrophys. J. 356, 682-686 S. J. Espinasse et al. 1991, Icarus 92, 350-365), while the second one is a kinetic model, calculating gas flow in tubes under the assumption of a known temperature distribution (N. I. Kömle and G. Dettleff 1991, Icarus 89, 73-84 Yu. V. Skorov et al. 1999, Icarus 140, 173-188). We review briefly the main aspects of this previous work, and subsequently present a combined consistent model, which uses a macroscopic heat transfer equation, but kinetic solutions for the gas flow. This new model was implemented as a numerical code and its performance is demonstrated by a couple of example calculations. The main advantage of the new model in comparison to the macroscopic approach is the fact that it avoids specifying a boundary condition for gas pressure at the surface, because the emitted gas flux is found at any time with the aid of the kinetic calculation. The local balance of sublimation and condensation in the interior of the porous ice can be calculated more consistently than is possible by macroscopic models only, because surface pressure and density develop in a ``natural'' way and no external boundary condition for the pressure must be imposed. We consider the development of temperature distribution and gas flux in ice samples in response to surface irradiation. Both pure ice and ice covered by a dust mantle are studied. The results are compared with corresponding solutions obtained on the basis of a macroscopic model, and differences are discussed in detail. Finally, experimental data obtained from previous comet simulation experiments (KOSI and related laboratory experiments) are reconsidered. In particular, temperature profiles and gas fluxes from the KOSI-9 experiment (E. Grün et al., 1993, J. Geophys. Res. 98, 15,091-15,104) are interpreted in terms of the kinetic approach.
Kargl Guenter
Kömle Norbert I.
Markiewicz Wojciech J.
Skorov Yu. V.
Uwe Keller Horst
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