Consistent treatment of transport properties for five-species air direct simulation Monte Carlo/Navier-Stokes applications

Stephani, Kelly A.; Goldstein, David; Varghese, Philip L.

doi:10.1063/1.4729610

Cited by 31 publications

(16 citation statements)

References 19 publications

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“…5. The mixture viscosity from the VHS and VSS models were determined 14 from the first-order Chapman-Enskog approximation of the mixture viscosity, defined as:…”

Section: Transport Properties and Model Parametersmentioning

confidence: 99%

Comparison of CFD and DSMC using calibrated transport parameters

Liechty

Wise

Subramaniam

et al. 2019

31st International Symposium on Rarefied Gas Dynamics: Rgd31

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Hypersonic re-entry flows span a wide range of length scales where regions of both rarefied and continuum flow exist. Traditional computational fluid dynamics (CFD) techniques do not provide an accurate solution for the rarefied regions of such 'mixed' flow fields. Although direct simulation Monte Carlo (DSMC) can be used to accurately capture both the continuum and rarefied features of 'mixed' flow fields, they are computationally expensive when employed to simulate the low Knudsen number continuum regimes. Thus, a hybrid framework for seamlessly combining the two methodologies, CFD and DSMC, continues to be a topic of significant research effort. Ensuring consistency in the reaction kinetics and transport models employed within CFD and DSMC is a crucial requirement for obtaining a reliable solution from a hybrid framework for combined continuum/rarefied high speed flows. This paper represents one of the first studies to utilize the calibrated transport parameters developed to ensure consistency between CFD and DSMC solvers. The new variable soft sphere (VSS) parameters are compared to both previous "standard" variable hard sphere (VHS) parameters and also to solutions from the CFD transport properties that the new parameters were developed to reproduce.

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“…5. The mixture viscosity from the VHS and VSS models were determined 14 from the first-order Chapman-Enskog approximation of the mixture viscosity, defined as:…”

Section: Transport Properties and Model Parametersmentioning

confidence: 99%

Comparison of CFD and DSMC using calibrated transport parameters

Liechty

Wise

Subramaniam

et al. 2019

31st International Symposium on Rarefied Gas Dynamics: Rgd31

Self Cite

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“…Therefore, within the limits of our current model atom-atom encounters can only result in elastic scattering. In Table IV we list the VHS parameters used in determining the elastic cross sections, adapted from Stephani et al 63 . We are aware that the listed VHS parameters are tuned to a much lower reference temperature than the conditions of our test case.…”

Section: Verification Of Dsmc Implementationmentioning

confidence: 99%

Coupling of state-resolved rovibrational coarse-grain model for nitrogen to stochastic particle method for simulating internal energy excitation and dissociation

Torres

Magin

2018

The Journal of Chemical Physics

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We propose to couple a state-resolved rovibrational coarse-grain model to a stochastic particle method for simulating internal energy excitation and dissociation of a molecular gas. A coarse-grained model for a rovibrational reaction mechanism of an ab initio database developed at NASA Ames Research Center for the N 2 -N system is modified based on variably-spaced energy bins. Thermodynamic properties of the modified coarse-grained model allow us to closely match those obtained with the full set of rovibrational levels over a wide temperature range, while using a number of bins significantly smaller than the complete mechanism. The chemical-kinetic behavior of equally-and variably-spaced bin formulations is compared by simulating internal energy excitation and dissociation of nitrogen in an adiabatic, isochoric reactor. We find that the variablyspaced formulation is better suited for reproducing the dynamics of the full database at conditions of interest in Earth atmospheric entry. Also in this paper, we discuss details of our particle method implementation for the URVC bin model and describe changes to the Direct Simulation Monte Carlo (DSMC) collision algorithm, which become necessary to accommodate our state-resolved reaction mechanism for excitation and dissociation reactions. The DSMC code is then verified against equivalent master equation calculations. In these simulations, state-resolved cross sections are used in analytical form. These cross sections verify micro-reversibility relations for the rovibrational bins and allow for fast execution of the DSMC code. In our verification calculations, we obtain very close agreement for the concentrations profiles of N and N 2 , as well as the translational and rovibrational mode temperatures obtained independently through both methods. In addition to macroscopic moments, we compare discrete internal energy populations predicted at selected time steps via DSMC and the master equations. We observe good agreement between the two sets of results within the limits imposed by statistical scatter, which is inherent to particle-based DSMC solutions. As future work, the rovibrational coarse-grain model coupled to the particle method will allow us to study 3D reentry flow configurations.

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“…23 The fitting of the DSMC transport coefficients to the CFD values is achieved through application of the Nelder-Mead Simplex Method, 24,25 which is used to determine the set of VHS and VSS model parameters that provide the best fit in the transport coefficients. 26 Before doing this, we first present the expressions used to determine the DSMC mixture diffusion, viscosity and thermal conductivity coefficients based on the VHS and VSS models.…”

Section: Consistent Treatment Of Transport Propertiesmentioning

confidence: 99%

Generation of a Hybrid DSMC/CFD Solution for Gas Mixtures with Internal Degrees of Freedom

Stephani

Goldstein²,

Varghese³

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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A consistent approach for generating a hybrid DSMC/CFD solution is presented for re-entry applications involving neutral gas mixtures with internal energy. A quality hybrid solution requires consistency in the thermo-chemical models employed by the particle (DSMC) and continuum (CFD) solvers, as well as an appropriate boundary condition for the transfer of flux information across the hybrid interface. The first half of this work focuses on achieving consistency in the transport properties obtained by particle and continuum solvers, including species diffusion, viscosity and translational and internal thermal conductivities for a five-species air mixture. In the second portion, a new approach for the generation of particles at a hybrid interface is presented for gas mixtures with internal degrees of freedom. Particle thermal velocities and internal energies are prescribed from the appropriate non-equilibrium (perturbed) distribution, in which diffusion, shear stress and heat flux terms are included in the Generalized Chapman-Enskog formulation of the perturbation. The significance of the contributions from these terms on the perturbation are examined at a hybrid interface within non-equilibrium boundary layer flow, as well as within the breakdown region near a normal shock, in a five-species air gas mixture. The validity of the Chapman-Enskog perturbation at each of these hybrid interfaces is assessed by comparison with the Generalized Chapman-Enskog perturbations. Nomenclature α VSS exponent D i scaled diffusion flux τ ij,s scaled shear stress q i,s scaled translational heat flux q i,s scaled internal heat flux d ref reference diameter T ref reference temperature ω temperature exponent α VSS scattering exponent g relative molecular collision speed D s effective diffusion coefficient D st binary diffusion coefficient χ mole fraction Y mass fraction

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Consistent treatment of transport properties for five-species air direct simulation Monte Carlo/Navier-Stokes applications

Cited by 31 publications

References 19 publications

Comparison of CFD and DSMC using calibrated transport parameters

Comparison of CFD and DSMC using calibrated transport parameters

Coupling of state-resolved rovibrational coarse-grain model for nitrogen to stochastic particle method for simulating internal energy excitation and dissociation

Generation of a Hybrid DSMC/CFD Solution for Gas Mixtures with Internal Degrees of Freedom

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