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On the Rarefied Gas Experiments

There are limits of validity of classical constitutive laws such as Fourier and Navier-Stokes equations. Phenomena beyond those limits have been experimentally found many decades ago. However, it is still not clear what theory would be appropriate to model different non-classical phenomena under dif...

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Detalles Bibliográficos
Autor principal: Kovács, Róbert
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7515232/
https://www.ncbi.nlm.nih.gov/pubmed/33267432
http://dx.doi.org/10.3390/e21070718
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author Kovács, Róbert
author_facet Kovács, Róbert
author_sort Kovács, Róbert
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description There are limits of validity of classical constitutive laws such as Fourier and Navier-Stokes equations. Phenomena beyond those limits have been experimentally found many decades ago. However, it is still not clear what theory would be appropriate to model different non-classical phenomena under different conditions considering either the low-temperature or composite material structure. In this paper, a modeling problem of rarefied gases is addressed. The discussion covers the mass density dependence of material parameters, the scaling properties of different theories and aspects of how to model an experiment. In the following, two frameworks and their properties are presented. One of them is the kinetic theory based Rational Extended Thermodynamics; the other one is the non-equilibrium thermodynamics with internal variables and current multipliers. In order to compare these theories, an experiment on sound speed in rarefied gases at high frequencies, performed by Rhodes, is analyzed in detail. It is shown that the density dependence of material parameters could have a severe impact on modeling capabilities and influences the scaling properties.
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spelling pubmed-75152322020-11-09 On the Rarefied Gas Experiments Kovács, Róbert Entropy (Basel) Article There are limits of validity of classical constitutive laws such as Fourier and Navier-Stokes equations. Phenomena beyond those limits have been experimentally found many decades ago. However, it is still not clear what theory would be appropriate to model different non-classical phenomena under different conditions considering either the low-temperature or composite material structure. In this paper, a modeling problem of rarefied gases is addressed. The discussion covers the mass density dependence of material parameters, the scaling properties of different theories and aspects of how to model an experiment. In the following, two frameworks and their properties are presented. One of them is the kinetic theory based Rational Extended Thermodynamics; the other one is the non-equilibrium thermodynamics with internal variables and current multipliers. In order to compare these theories, an experiment on sound speed in rarefied gases at high frequencies, performed by Rhodes, is analyzed in detail. It is shown that the density dependence of material parameters could have a severe impact on modeling capabilities and influences the scaling properties. MDPI 2019-07-23 /pmc/articles/PMC7515232/ /pubmed/33267432 http://dx.doi.org/10.3390/e21070718 Text en © 2019 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Kovács, Róbert
On the Rarefied Gas Experiments
title On the Rarefied Gas Experiments
title_full On the Rarefied Gas Experiments
title_fullStr On the Rarefied Gas Experiments
title_full_unstemmed On the Rarefied Gas Experiments
title_short On the Rarefied Gas Experiments
title_sort on the rarefied gas experiments
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7515232/
https://www.ncbi.nlm.nih.gov/pubmed/33267432
http://dx.doi.org/10.3390/e21070718
work_keys_str_mv AT kovacsrobert ontherarefiedgasexperiments