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Turbulent chemical-species mixing in the Venus lower atmosphere at different altitudes: A Direct Numerical Simulation study relevant to understanding species spatial distribution

Morellina, Stefano and Bellan, Josette (2022) Turbulent chemical-species mixing in the Venus lower atmosphere at different altitudes: A Direct Numerical Simulation study relevant to understanding species spatial distribution. Icarus, 371 . Art. No. 114686. ISSN 0019-1035. doi:10.1016/j.icarus.2021.114686. https://resolver.caltech.edu/CaltechAUTHORS:20210927-225706581

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Abstract

To evaluate a recent hypothesis of species stratification in the Venus lower atmosphere, a time-dependent, three-dimensional model is proposed for studying turbulent mixing of many species in the Venus lower atmosphere. This model is based on fundamental physics embedding non-equilibrium thermodynamics, the Onsager classical relationship between fluxes and forces, high-pressure transport property calculation and a real-gas equation of state. The conservation equations are self-contained, with no need for coefficients based on parametrizations to match Venus observations. The rationale for solving these equations in relatively small spatial domains at different altitudes in the Venus lower atmosphere is presented. The equations are solved in a temporal mixing layer configuration that is eminently suited to investigate turbulent mixing between two streams of different composition. The adopted simulation method is Direct Numerical Simulation (DNS). A substantial database of DNS realizations is generated for mixtures of two and seven species, with different levels of initial stratification, and at the realistic conditions of pressures and temperatures in the Venus lower atmosphere at three altitudes. High density-gradient magnitude regions (HDGM) are shown to form under initial high stratification conditions, with larger gradient values obtained at low altitudes where supercritical conditions occur. Independent of the altitude lower than 50 km, under low stratification conditions, mixing produces a more uniform spatial distribution of the density than at higher initial stratification. Under low initial stratification conditions, the influence of the minor species on the global behavior of the flow seems to be negligible. At high initial stratification conditions, differences in diffusion of various species play an important role in determining the mixture characteristics. The hypothesis of chemical species separation is discussed in the light of the present results which do not support the existence of stable species separation in the lower Venus atmosphere, independent of the number of species or the altitude.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.icarus.2021.114686DOIArticle
ORCID:
AuthorORCID
Bellan, Josette0000-0001-9218-7017
Additional Information:© 2021 Elsevier. Received 26 October 2020, Revised 23 August 2021, Accepted 25 August 2021, Available online 10 September 2021. This work was conducted at the Jet Propulsion Laboratory (JPL) of the California Institute of Technology (Caltech) and sponsored by JPL internal development funds. This study is part of Stefano Morellina’s (SM) Master thesis and was performed while he was an intern at JPL. The contributions of Dr. Aswin Gnanaskandan and Dr. Luca Sciacovelli in helping SM understand the DNS code are thankfully recognized. Stefano Morellina’s Master thesis supervisor, Dr. Francesco Creta, and the co-supervisor, Dr. Pasquale E. Lapenna, are thanked for their advice. The Institut Supérieur de l’Aéronautique et de l’Espace (ISAE-SUPAERO), the Sapienza University of Rome, and the Italian Space Agency are thanked for providing support to SM during his internship at JPL. The computational resources were provided by the NASA Advanced Supercomputing at Ames Research Center under the Science Mission Directorate program. The discussions with and guidance from Dr. J. Cutts of JPL are gratefully acknowledged.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
JPL Internal Research and Technology Development ProgramUNSPECIFIED
Institut Supérieur de l’Aé ronautique et de l’EspaceUNSPECIFIED
Sapienza University of RomeUNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Subject Keywords:Venus lower atmosphere turbulent species mixing at several altitudes
DOI:10.1016/j.icarus.2021.114686
Record Number:CaltechAUTHORS:20210927-225706581
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210927-225706581
Official Citation:Stefano Morellina, Josette Bellan, Turbulent chemical-species mixing in the Venus lower atmosphere at different altitudes: A Direct Numerical Simulation study relevant to understanding species spatial distribution, Icarus, Volume 371, 2022, 114686, ISSN 0019-1035, https://doi.org/10.1016/j.icarus.2021.114686.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111076
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Sep 2021 14:42
Last Modified:07 Oct 2021 21:47

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