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Titel |
Gas flow in the near-surface porous boundary layer of the
67P/Churyumov-Gerasimenko using micro-CT images |
VerfasserIn |
Chariton Christou, S. Kokou Dadzie, Nicolas Thomas, Paul Hartogh, Laurent Jorda, Ekkehard Kührt, James Whitby, Ian Wright, John Zarnecki |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250139440
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Publikation (Nr.) |
EGU/EGU2017-2679.pdf |
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Zusammenfassung |
While ESA’s Rosetta mission has formally been completed, the data analysis and
interpretation continues. Here, we address the physics of the gas flow at the surface of the
comet. Understanding the sublimation of ice at the surface of the nucleus provides the initial
boundary condition for studying the inner coma. The gas flow at the surface of
the comet 67P/Churyumov-Gerasimenko can be in the rarefaction regime and a
non-Maxwellian velocity distribution may be present. In these cases, continuum methods like
Navier-Stokes-Fourier (NSF) set of equations are rarely applicable. Discrete particle methods
such as Direct Simulation Monte Carlo (DSMC) method are usually adopted. DSMC is
currently the dominant numerical method to study rarefied gas flows. It has been
widely used to study cometary outflow over past years .1,2. In the present study, we
investigate numerically, gas transport near the surface of the nucleus using DSMC.
We focus on the outgassing from the near surface boundary layer into the vacuum
(∼20 cm above the nucleus surface). Simulations are performed using the open
source code dsmcFoam on an unstructured grid. Until now, artificially generated
random porous media formed by packed spheres have been used to represent the
comet surface boundary layer structure .3. In the present work, we used instead
Micro-computerized-tomography (micro-CT) scanned images to provide geologically
realistic 3D representations of the boundary layer porous structure. The images are from earth
basins. The resolution is relatively high - in the range of some μm. Simulations from
different rock samples with high porosity (and comparable to those expected at 67P)
are compared. Gas properties near the surface boundary layer are presented and
characterized. We have identified effects of the various porous structure properties
on the gas flow fields. Temperature, density and velocity profiles have also been
analyzed.
.1. J.-F. Crifo, G. Loukianov, A. Rodionov and V. Zakharov, Icarus 176 (1), 192-219
(2005).
2. Y. Liao, C. Su, R. Marschall, J. Wu, M. Rubin, I. Lai, W. Ip, H. Keller, J. Knollenberg
and E. Kührt, Earth, Moon, and Planets 117 (1), 41-64 (2016).
3. Y. V. Skorov, R. Van Lieshout, J. Blum and H. U. Keller, Icarus 212 (2), 867-876
(2011). |
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