Large-Eddy Simulation of Supercritical-Pressure Round Jets

A comprehensive numerical framework has been established to simulate reacting §ows under conditions typically encountered in rocket combustion chambers. The model implemented into the commercial CFD Code ANSYS CFX includes appropriate real gas relations based on the volume-corrected PengRobinson (PR) equation of state (EOS) for the §ow ¦eld and a real gas extension of the laminar §amelet combustion model. The results indicate that the real gas relations have a considerably larger impact on the §ow ¦eld than on the detailed §ame structure. Generally, a realistic §ame shape could be achieved for the real gas approach compared to experimental data from the Mascotte test rig V03 operated at ONERA when the di¨erential di¨usion processes were only considered within the §ame zone.

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“…The Real 2 approach is used for this purpose with and without modeling thermal di¨usion e¨ects according to Eq. (16).…”

Section: In §Uence Of Thermal Di¨usion and Pressurementioning

confidence: 99%

Real gas CFD simulations of hydrogen/oxygen supercritical combustion

Pohl

Jarczyk

Pfitzner

et al. 2013

Progress in Propulsion Physics

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“…Studies related to LES have been reported in [19,20]. Thereby, the subgrid scale (SGS) models applied have been developed for subcritical flow conditions.…”

Section: Introductionmentioning

confidence: 99%

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

Ries

Janicka

Sadiki

2017

Entropy

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Abstract:In the present paper, thermal transport and entropy production mechanisms in a turbulent round jet of compressed nitrogen at supercritical thermodynamic conditions are investigated using a direct numerical simulation. First, thermal transport and its contribution to the mixture formation along with the anisotropy of heat fluxes and temperature scales are examined. Secondly, the entropy production rates during thermofluid processes evolving in the supercritical flow are investigated in order to identify the causes of irreversibilities and to display advantageous locations of handling along with the process regimes favorable to mixing. Thereby, it turned out that (1) the jet disintegration process consists of four main stages under supercritical conditions (potential core, separation, pseudo-boiling, turbulent mixing), (2) causes of irreversibilities are primarily due to heat transport and thermodynamic effects rather than turbulence dynamics and (3) heat fluxes and temperature scales appear anisotropic even at the smallest scales, which implies that anisotropic thermal diffusivity models might be appropriate in the context of both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) approaches while numerically modeling supercritical fluid flows.

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“…Inside the mixing layer, C p and C q are both bounded in [0.7, 2.2] while C J α ∈ [0. 5,3]. This shows that in the region of activity, the coefficients are positive and vary within a small range, thereby showing that they are well-conditioned and boding well for stable LES.…”

Section: Modeling Of P(φ) Q(φ) and J α (φ)mentioning

confidence: 67%

“…7 The domain size in the streamwise (L 1 ) and spanwise (L 3 ) directions is such that it accommodates initially four vortices associated with the wavelengths λ 1 and λ 3 of perturbations, 8 respectively. The domain lengths, L i (i = [1,3]), were the same for all simulations and are listed in the caption of Table II. The cross-stream domain size (L 2 ) is large enough so that there is no interference of the mixing region with the domain boundaries.…”

Section: Description Of the Dns Databasementioning

confidence: 99%

A priori and a posteriori investigations for developing large eddy simulations of multi-species turbulent mixing under high-pressure conditions

Borghesi

Bellan

2015

Physics of Fluids

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A Direct Numerical Simulation (DNS) database was created representing mixing of species under high-pressure conditions. The configuration considered is that of a temporally evolving mixing layer. The database was examined and analyzed for the purpose of modeling some of the unclosed terms that appear in the Large Eddy Simulation (LES) equations. Several metrics are used to understand the LES modeling requirements. First, a statistical analysis of the DNS-database large-scale flow structures was performed to provide a metric for probing the accuracy of the proposed LES models as the flow fields obtained from accurate LESs should contain structures of morphology statistically similar to those observed in the filtered-and-coarsened DNS (FC-DNS) fields. To characterize the morphology of the large-scales structures, the Minkowski functionals of the iso-surfaces were evaluated for two different fields: the second-invariant of the rate of deformation tensor and the irreversible entropy production rate. To remove the presence of the small flow scales, both of these fields were computed using the FC-DNS solutions. It was found that the large-scale structures of the irreversible entropy production rate exhibit higher morphological complexity than those of the second invariant of the rate of deformation tensor, indicating that the burden of modeling will be on recovering the thermodynamic fields. Second, to evaluate the physical effects which must be modeled at the subfilter scale, an a priori analysis was conducted. This a priori analysis, conducted in the coarse-grid LES regime, revealed that standard closures for the filtered pressure, the filtered heat flux, and the filtered species mass fluxes, in which a filtered function of a variable is equal to the function of the filtered variable, may no longer be valid for the high-pressure flows considered in this study. The terms requiring modeling are the filtered pressure, the filtered heat flux, the filtered pressure work, and the filtered species mass fluxes. Improved models were developed based on a scale-similarity approach and were found to perform considerably better than the classical ones. These improved models were also assessed in an a posteriori study. Different combinations of the standard models and the improved ones were tested. At the relatively small Reynolds numbers achievable in DNS and at the relatively small filter widths used here, the standard models for the filtered pressure, the filtered heat flux, and the filtered species fluxes were found to yield accurate results for the morphology of the large-scale structures present in the flow. Analysis of the temporal evolution of several volume-averaged quantities representative of the mixing layer growth, and of the cross-stream variation of homogeneous-plane averages and second-order correlations, as well as of visualizations, indicated that the models performed equivalently for the conditions of the simulations. The expectation is that at the much larger Reynolds numbers and much larger filter widths used in practical applications, the improved models will have much more accurate performance than the standard one.

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Large-Eddy Simulation of Supercritical-Pressure Round Jets

Cited by 132 publications

References 44 publications

Real gas CFD simulations of hydrogen/oxygen supercritical combustion

Real gas CFD simulations of hydrogen/oxygen supercritical combustion

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

A priori and a posteriori investigations for developing large eddy simulations of multi-species turbulent mixing under high-pressure conditions

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