Supercritical nitrogen free jet investigated by spontaneous Raman scattering

Oschwald, Michael; Schik, A.

doi:10.1007/s003480050374

Cited by 146 publications

(69 citation statements)

References 16 publications

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“…Moreover, we already know that the flows of present interest have distinct inhomogeneities, [6][7][8][9][10][11] in which case duplicating the local aspect of the flow may be important. Indeed, local inhomogeneities affect turbulence production 7,27 as well as phase separation.…”

Section: Resultsmentioning

confidence: 99%

“…10,11 Accurate LES would reproduce the salient properties of these flows, meaning that not only spatially averaged values and rms of several fluid-dynamics variables, such as the velocity components, would be captured but also that the spatial statistical occurrence of large-scale structures within the flow would be correctly represented. To characterize the large-scale distortion of a turbulent flow, we examine the spatial distributions of two important quantities: the second invariant of the rate of deformation tensor, 30 I I d , which addresses the dynamic aspects of the flow, and the irreversible entropy production rate g, which primarily addresses the thermodynamics.…”

Section: A Statistical Analysis Of Flow Characteristics At T * Trmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: A Statistical Analysis Of Flow Characteristics At T * Trmentioning

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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“…Then, it was applied to investigate the density and temperature distributions of supercritical nitrogen jets (Oschwald and Schik, 1999;Branam and Mayer, 2003). In general, the normalized density profiles in the downstream indicated a tendency towards the self-similarity solution observed for classical constant-and variable-density single-phase fluid jets at low pressures.…”

Section: ^F^^s^^f^w/mentioning

confidence: 95%

Liquid-Propellant Rocket Engine Injector Dynamics and Combustion Processes at Supercritical Conditions

Yang¹

2004

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“…2) It has been reported that under such conditions, the liquid break-up process is not observable [3][4][5] and the mixing of fuel and oxidizer likely takes place in the same way as in the single-phase gaseous diffusion. This hypothesis is supported by various analyses of experimental data.…”

Section: Introductionmentioning

confidence: 99%

“…This hypothesis is supported by various analyses of experimental data. 4,[6][7][8] Consequently, it may be possible to apply gaseous single-phase flow simulation techniques to the simulation of combusting flows in a chamber at supercritical pressure.…”

Section: Introductionmentioning

confidence: 99%

One-Dimensional H2/O2 Counterflow Diffusion Flame Simulation for Flamelet Table Construction at Supercritical Pressure

Mizobuchi

Hirakawa

2013

Trans. Japan Soc. Aero. S Sci.

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Supercritical fluid properties are implemented in a one-dimensional counterflow flame simulation code using the Soave-Redlich-Kwong equation of state and modifying the transport properties for high-pressure, low-temperature conditions. Examination of a GH 2 /LOX diffusion flame at supercritical pressure reveals an extremely fine structure at the edge of the oxygen diffusion layer, indicating that a DNS-like approach to simulation of such flames is not practical in the near term, and flame modeling must be used. To investigate flamelet table construction, we compare simulations that use supercritical fluid and standard temperature and pressure (STP) gas properties. Both types of simulations are shown to produce almost identical flame structures when we parameterize the flame with the scalar dissipation rate at its stoichiometric position. The results show that the use of STP gas property simulation is expected to be an effective means of greatly reducing the computational cost of constructing flamelet tables at supercritical pressures.

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Supercritical nitrogen free jet investigated by spontaneous Raman scattering

Cited by 146 publications

References 16 publications

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

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

Liquid-Propellant Rocket Engine Injector Dynamics and Combustion Processes at Supercritical Conditions

One-Dimensional H2/O2 Counterflow Diffusion Flame Simulation for Flamelet Table Construction at Supercritical Pressure

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