Direct Molecular Simulation of Nonequilibrium Dilute Gases

Schwartzentruber, Thomas E.; Grover, Maninder S.; Valentini, Paolo

doi:10.2514/1.t5188

Cited by 85 publications

(31 citation statements)

References 32 publications

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“…In our review, we have also reported the calculation of VV and VT rates of CO 2 by using the QCT method with a semi-empirical potential energy surface. A more detailed method for VV and VT processes of O 2 -O-N 2 components uses an ab-initio quantum mechanical method for the potential energy surface [239]. No ab-initio calculations exist for the dissociation of CO 2 by heavy-particle impact.…”

Section: O 2 and Omentioning

confidence: 99%

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

et al. 2021

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Numerous applications have required the study of CO2 plasmas since the 1960s, from CO2 lasers to spacecraft heat shields. However, in recent years, intense research activities on the subject have restarted because of environmental problems associated with CO2 emissions. The present review provides a synthesis of the current state of knowledge on the physical chemistry of cold CO2 plasmas. In particular, the different modeling approaches implemented to address specific aspects of CO2 plasmas are presented. Throughout the paper, the importance of conducting joint experimental, theoretical and modeling studies to elucidate the complex couplings at play in CO2 plasmas is emphasized. Therefore, the experimental data that are likely to bring relevant constraints to the different modeling approaches are first reviewed. Second, the calculation of some key elementary processes obtained with semi-empirical, classical and quantum methods is presented. In order to describe the electron kinetics, the latest coherent sets of cross section satisfying the constraints of "electron swarm" analyses are introduced, and the need for self-consistent calculations for determining accurate electron energy distribution function (EEDF) is evidenced. The main findings of the latest zero-dimensional (0D) global models about the complex chemistry of CO2 and its dissociation products in different plasma discharges are then given, and full state-to-state (STS) models of only the vibrational-dissociation kinetics developed for studies of spacecraft shields are described. Finally, two important points for all applications using CO2 containing plasma are discussed: the role of surfaces in contact with the plasma, and the need for 2D/3D models to capture the main features of complex reactor geometries including effects induced by fluid dynamics on the plasma properties. In addition to bringing together the latest advances in the description of CO2 non-equilibrium plasmas, the results presented here also highlight the fundamental data that are still missing and the possible routes that still need to be investigated.

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Section: O 2 and Omentioning

confidence: 99%

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

et al. 2021

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“…The method was implemented by using modern DSMC algorithms by Norman et al (40) and extended to rotating, vibrating, and dissociating molecules by using ab initio PESs in a series of articles by Valentini et al (15,33,41,42). The details of the DMS method have been summarized in a recent review article by Schwartzentruber et al (43). Fig.…”

Section: Ab Initio Resultsmentioning

confidence: 99%

Nonequilibrium internal energy distributions during dissociation

Singh

Schwartzentruber

2017

Proc. Natl. Acad. Sci. U.S.A.

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In this work, we propose a model for nonequilibrium vibrational and rotational energy distributions in nitrogen using surprisal analysis. The model is constructed by using data from direct molecular simulations (DMSs) of rapidly heated nitrogen gas using an ab initio potential energy surface (PES). The surprisal-based model is able to capture the overpopulation of high internal energy levels during the excitation phase and also the depletion of high internal energy levels during the quasi-steady-state (QSS) dissociation phase. Due to strong coupling between internal energy and dissociation chemistry, such non-Boltzmann effects can influence the overall dissociation rate in the gas. Conditions representative of the flow behind strong shockwaves, relevant to hypersonic flight, are analyzed. The surprisal-based model captures important molecular-level nonequilibrium physics, yet the simple functional form leads to a continuum-level expression that now accounts for the underlying energy distributions and their coupling to dissociation.

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“…The core DMS algorithm is relatively straight-forward and has been described in detail in prior publications [12,49,50]. The DMS calculations presented in this article focus only on internal energy transfer and dissociation processes for N 2 -N 2 collisions.…”

Section: Direct Molecular Simulation Methodsmentioning

confidence: 99%

Comparison of Potential Energy Surface and Computed Rate Coefficients for N2 Dissociation

Jaffe

Grover

Venturi

et al. 2018

Journal of Thermophysics and Heat Transfer

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Comparisons are made between potential energy surfaces (PES) for N 2 + N and N 2 + N 2 collisions and between rate coefficients for N 2 dissociation that were computed using the quasiclassical trajectory method (QCT) on these PESs. For N 2 + N we compare the Laganà's empirical LEPS surface with one from NASA Ames Research Center based on ab initio quantum chemistry calculations. For N 2 + N 2 we compare two ab initio PESs (from NASA Ames and from the University of Minnesota). These use different methods for computing the ground state electronic energy for N 4 , but give similar results. Thermal N 2 dissociation rate coefficients, for the 10,000K-30,000K temperature range, have been computed using each PES and the results are in excellent agreement. Quasi-stationary state (QSS) rate coefficients using both PESs have been computed at these temperatures using the Direct Molecular Simulation of Schwartzentruber and coworkers. The QSS rate coefficients are up to a factor of 5 lower than the thermal ones and the thermal and QSS values bracket the results of shock-tube experiments. We conclude that the

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Direct Molecular Simulation of Nonequilibrium Dilute Gases

Cited by 85 publications

References 32 publications

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

Nonequilibrium internal energy distributions during dissociation

Comparison of Potential Energy Surface and Computed Rate Coefficients for N2 Dissociation

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