Oxygen transport properties estimation by classical trajectory–direct simulation Monte Carlo

Bruno, D.; Frezzotti, Aldo; Ghiroldi, Gian Pietro

doi:10.1063/1.4921157

Cited by 20 publications

(13 citation statements)

References 45 publications

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“…Following Refs. [22][23][24], effective values of the thermal conductivity are used to estimate its Chapman-Enskog limit. The properties including the characteristic vibrational temperatures of all gases examined in the present work are given in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies (see [22,23] and references therein for monatomic gases and [24] for a diatomic gas), have shown that k eff ðyÞ approximates extremely well the Chapman-Enskog value of the thermal conductivity in a central strip of the domain, provided its boundaries are sufficiently far from the walls where the Knudsen layers cause deviations from the hydrodynamic behavior. The computed k eff ðyÞ is plotted in Fig.…”

Section: Gasmentioning

confidence: 93%

“…Next, they are substituted into the moment Eqs. (24) to yield analytical results for the macroscopic distributions. It is noted that in the free molecular limit all moments remain constant at any position between the plates.…”

Section: Appendix a Relaxation Rates In A Homogenous Gasmentioning

confidence: 99%

“…(22) and (23) are solved numerically discretizing in the physical space by the control volume approach and in the molecular velocity space by the discrete velocity method to yield the reduced distributions F, L, H and K, which are introduced into the moment Eqs. (24) and (28). Integration is performed via the Gauss-Legendre quadrature to find the new estimates of all bulk quantities which are introduced in the next iteration.…”

Section: The Holway Kinetic Modelmentioning

confidence: 99%

“…The influence of the vibrational degrees of freedom on the heat fluxes for CO 2 , CH 4 and SF 6 at low reference temperatures is investigated, while corresponding high temperature calculations with N 2 and O 2 is mainly performed for model testing and results validation. Furthermore, thermal conductivities predicted by the considered gas models have been estimated exploiting the good agreement between the kinetic solutions and their hydrodynamic (Chapman-Enskog) approximations, which occurs, even for moderately high values of the rarefaction parameter in a central strip of the domain [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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Effect of vibrational degrees of freedom on the heat transfer in polyatomic gases confined between parallel plates

Tantos

Ghiroldi

Valougeorgis

et al. 2016

International Journal of Heat and Mass Transfer

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Conductive stationary heat transfer through rarefied nonpolar polyatomic gases, confined between parallel plates maintained at different temperatures, is investigated. It is assumed that gas molecules possess both rotational and vibrational degrees of freedom, described by the classical rigid rotator and quantum harmonic oscillator models, respectively. The flow structure is computed by the Holway kinetic model and the Direct Simulation Monte Carlo method. In both approaches the total collision frequency is computed according to the Inverse Power Law intermolecular potential. Inelastic collisions in DSMC simulations are based on the quantum version of the Borgnakke–Larsen collision model. Results are presented for N2, O2, CO2, CH4 and SF6 representing diatomic as well as linear and nonlinear polyatomic molecules with 1 up to 15 vibrational modes. The translational, rotational, vibrational and total temperatures and heat fluxes are computed in a wide range of the rarefaction parameter and for various ratios of the hot over the cold plate temperatures. Very good agreement, between the Holway and DSMC results is observed as well as with experiments. The effect of the vibrational degrees of freedom is demonstrated. In diatomic gases the vibrational heat flux varies from 5% up to 25% of the total one. Corresponding results in polyatomic gases with a higher number of vibrational modes show that even at low reference temperatures the contribution of the vibrational heat flux may be considerably higher. For example in the case of SF6 at 300 K and 500 K the vibrational heat flux is about 67% and 76% respectively of the total heat flux. Furthermore, it is numerically proved that the computed solutions are in agreement with the Chapman–Enskog approximation in a central strip of the computational domain even at moderately large values of the rarefaction parameter, as found in previous investigations. This property has been used to compute the gas thermal conductivity predicted by the adopted models

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Section: Resultsmentioning

confidence: 99%