Parallel three-dimensional direct simulation Monte Carlo method and its applications

Wu, Jong‐Shinn; Lian, Y. Y.

doi:10.1016/s0045-7930(02)00083-x

“…Our code for modelling the coma, named PDSC ++ (Su 2013), has previously been used to model the water vapour distribution in the vicinity of comet 9P/Tempel 1 (Finklenburg et al 2014) and is based on the PDSC code developed by Wu and co-workers (Wu & Lian 2003;Wu et al 2004;Wu & Tseng 2005). PDSC ++ allows a simulation of 2D, 2D-axisymmetric, and 3D flows on hybrid unstructured grids.…”

Section: Dsmc Methodsmentioning

confidence: 99%

Modelling observations of the inner gas and dust coma of comet 67P/Churyumov-Gerasimenko using ROSINA/COPS and OSIRIS data: First results

Marschall

¹

,

Su

²

,

Liao

³

et al. 2016

A&A

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Context. This paper describes the initial modelling of gas and dust data acquired in August and September 2014 from the European Space Agency's Rosetta spacecraft when it was in close proximity to the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. This work is an attempt to provide a self-consistent model of the innermost gas and dust coma of the comet, as constrained by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) data set for the gas and by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) data set for the dust. Methods. The model uses a previously developed shape model for the nucleus, and from this the water sublimation rate and gas temperatures at the surface are computed with a simple thermal model. The gas expansion is modelled with a 3D parallel implementation of a Direct Simulation Monte Carlo algorithm. A dust drag algorithm is then used to produce dust densities in the coma, which are then converted to brightnesses using Mie theory and a line-of-sight integration. Results. We show that a purely insolation-driven model for surface outgassing does not produce a reasonable fit to ROSINA/COPS data. A stronger source in the "neck" region of the nucleus (region Hapi) is needed to match the observed modulation of the gas density in detail. This agrees with OSIRIS data, which shows that the dust emission from the "neck" was dominant in the August-September 2014 time frame. The current model matches this observation reasonably if a power index of 2-3 for the dust size distribution is used. A better match to the OSIRIS data is seen by using a single large particle size for the coma. Conclusions. We have shown possible solutions to the gas and dust distributions in the inner coma, which are consistent with ROSINA and OSIRIS data.

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“…This code has been used previously to model the water vapor distribution in the vicinity of comet 9P/Tempel 1 (Finklenburg et al 2014). PDSC ++ (Su 2013) is based on the PDSC code developed by Wu and co-workers (Wu & Lian 2003;Wu & Tseng 2005;Wu et al 2004). PDSC ++ allows a simulation of 2D, 2D-axisymmetric, and 3D flows on hybrid unstructured grids.…”

Section: Influence Of Gas Dragmentioning

confidence: 99%

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Thomas¹,

Davidsson²,

El-Maarry³

et al. 2016

Geological Society of America Abstracts With Programs

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Context. We present an investigation of the surface properties of areas on the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. We aim to show that transport of material from one part of the cometary nucleus to another is a significant mechanism that influences the appearance of the nucleus and the surface thermal properties. Methods. We used data from the OSIRIS imaging system onboard the Rosetta spacecraft to identify surface features on the nucleus that can be produced by various transport mechanisms. We used simple calculations based on previous works to establish the plausibility of dust transport from one part of the nucleus to another. Results. We show by observation and modeling that "airfall" as a consequence of non-escaping large particles emitted from the neck region of the nucleus is a plausible explanation for the smooth thin deposits in the northern hemisphere of the nucleus. The consequences are also discussed. We also present observations of aeolian ripples and ventifacts. We show by numerical modeling that a type of saltation is plausible even under the rarified gas densities seen at the surface of the nucleus. However, interparticle cohesive forces present difficulties for this model, and an alternative mechanism for the initiation of reptation and creep may result from the airfall mechanism. The requirements on gas density and other parameters of this alternative make it a more attractive explanation for the observations. The uncertainties and implications are discussed.

show abstract

“…This code has been used previously to model the water vapor distribution in the vicinity of comet 9P/Tempel 1 (Finklenburg et al 2014). PDSC ++ (Su 2013) is based on the PDSC code developed by Wu and co-workers (Wu & Lian 2003;Wu & Tseng 2005;Wu et al 2004). PDSC ++ allows a simulation of 2D, 2D-axisymmetric, and 3D flows on hybrid unstructured grids.…”

Section: Influence Of Gas Dragmentioning

confidence: 99%

Redistribution of particles across the nucleus of comet 67P/Churyumov-Gerasimenko

Thomas

¹

,

Davidsson

²

,

El‐Maarry

³

et al. 2015

A&A

View full text Add to dashboard Cite

Context. We present an investigation of the surface properties of areas on the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. We aim to show that transport of material from one part of the cometary nucleus to another is a significant mechanism that influences the appearance of the nucleus and the surface thermal properties. Methods. We used data from the OSIRIS imaging system onboard the Rosetta spacecraft to identify surface features on the nucleus that can be produced by various transport mechanisms. We used simple calculations based on previous works to establish the plausibility of dust transport from one part of the nucleus to another. Results. We show by observation and modeling that "airfall" as a consequence of non-escaping large particles emitted from the neck region of the nucleus is a plausible explanation for the smooth thin deposits in the northern hemisphere of the nucleus. The consequences are also discussed. We also present observations of aeolian ripples and ventifacts. We show by numerical modeling that a type of saltation is plausible even under the rarified gas densities seen at the surface of the nucleus. However, interparticle cohesive forces present difficulties for this model, and an alternative mechanism for the initiation of reptation and creep may result from the airfall mechanism. The requirements on gas density and other parameters of this alternative make it a more attractive explanation for the observations. The uncertainties and implications are discussed.

show abstract

Parallel three-dimensional direct simulation Monte Carlo method and its applications

Cited by 58 publications

References 22 publications

Modelling observations of the inner gas and dust coma of comet 67P/Churyumov-Gerasimenko using ROSINA/COPS and OSIRIS data: First results

Modelling observations of the inner gas and dust coma of comet 67P/Churyumov-Gerasimenko using ROSINA/COPS and OSIRIS data: First results

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Redistribution of particles across the nucleus of comet 67P/Churyumov-Gerasimenko

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