Turbulence Resolution Scale Dependence in Large-Eddy Simulations of a Jet Flame

Kemenov, Konstantin A.; Wang, Haifeng; Pope, Stephen B.

doi:10.1007/s10494-011-9380-x

Cited by 16 publications

(11 citation statements)

References 44 publications

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“…The modeling constant in the localized dynamic Smagorinsky model used here decreases to zero in laminar regions making this model suitable also for low-turbulence regions investigated here. However, other choices like Vreman (Vreman, 2004) or static Sigma (Nicoud et al, 2011) models are possible and these models are expected to give improvements only close to walls or in transitional regions (Kemenov et al, 2012;Rieth et al, 2014;Vreman, 2004) (not relevant for this study). Furthermore, these models involve additional model constants (thus their tuning) and so they are not considered for this study.…”

Section: Governing Equationsmentioning

confidence: 99%

Large-Eddy Simulation of Premixed Combustion in the Corrugated-Flamelet Regime

Langella

Swaminathan

Williams

et al. 2016

Combustion Science and Technology

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Large-eddy simulation (LES) is applied to a fuel-lean turbulent propane-air Bunsen flame in the corrugated-flamelet regime. The subgrid-scale (SGS) modeling includes a previously developed treatment of the total enthalpy along with three different SGS velocity, u 0 Δ , models. In addressing the filtered reaction rate, a presumed probability density function (PDF) approach is employed for the reactionprogress variable, closed by a transport equation for its SGS variance. The statistics obtained using the three u 0 Δ models are in good agreement with the measurements and do not differ significantly from each other for first-order moments suggesting that commonly used SGS modeling may be adequate to get the mean velocities and reaction progress variable. However, all three SGS velocity models fail to reflect a measured bimodality of the PDF of the radial component of the velocity in the central portion of the flame. This emphasizes a need for further development of u 0 Δ models required at the reaction rate closure level for practical LES of combustion in the corrugated-flamelet regime.

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Section: Governing Equationsmentioning

confidence: 99%

Large-Eddy Simulation of Premixed Combustion in the Corrugated-Flamelet Regime

Langella

Swaminathan

Williams

et al. 2016

Combustion Science and Technology

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“…Issues therefore arise because the filter is defined to be equal or close to the grid size. Because of this, in solving the velocity field, LES results exhibit a dependence both on the grid resolution and on the numerical methods (e.g., Pope 2004;Geurts 2006;Kemenov et al 2012). Avoiding these issues requires a clear gap between the filter width (and related mixing length in the SGS model) and the grid size (e.g.…”

Section: Large-eddy Simulationmentioning

confidence: 99%

Concentration Fluctuations from Localized Atmospheric Releases

Cassiani

Bertagni

Marro

et al. 2020

Boundary-Layer Meteorol

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We review the efforts made by the scientific community in more than seventy years to elucidate the behaviour of concentration fluctuations arising from localized atmospheric releases of dynamically passive and non-reactive scalars. Concentration fluctuations are relevant in many fields including the evaluation of toxicity, flammability, and odour nuisance. Characterizing concentration fluctuations requires not just the mean concentration but also at least the variance of the concentration in the location of interest. However, for most purposes the characterization of the concentration fluctuations requires knowledge of the concentration probability density function (PDF) in the point of interest and even the time evolution of the concentration. We firstly review the experimental works made both in the field and in the laboratory, and cover both point sources and line sources. Regarding modelling approaches, we cover analytical, semi-analytical, and numerical methods. For clarity of presentation we subdivide the models in two groups, models linked to a transport equation, which usually require a numerical resolution, and models mainly based on phenomenological aspects of dispersion, often providing analytical or semi-analytical relations. The former group includes: large-eddy simulations, Reynolds-averaged Navier–Stokes methods, two-particle Lagrangian stochastic models, PDF transport equation methods, and heuristic Lagrangian single-particle methods. The latter group includes: fluctuating plume models, semi-empirical models for the concentration moments, analytical models for the concentration PDF, and concentration time-series models. We close the review with a brief discussion highlighting possible useful additions to experiments and improvements to models.

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“…The computational grid for this study was based on the "M4" grid in the LES study of Flame D by Kemenov, et al [35]. This grid spanned a cylindrical region of 100D x 20D x 2, where D is the jet diameter.…”

Section: X2 Numerical Formulationmentioning

confidence: 99%

“…This grid spanned a cylindrical region of 100D x 20D x 2, where D is the jet diameter. This grid was shown to be grid resolved using a similar discretion and solution procedure as used in this study [35]. This grid extended upstream of the nozzle exit plane 0.3D in the co-flow region and included approximately 2.7M grid points in a 216 x 156 x 80 arrangement.…”

Section: X2 Numerical Formulationmentioning

confidence: 99%

Strain Effects in Partially Premixed Methane-air Jet Flames

Calhoon

Kemenov

2015

53rd AIAA Aerospace Sciences Meeting

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A large-eddy simulation (LES) subgrid combustion model has been developed based on an innovative application of the linear-eddy model to the counter flow configuration (LEM-CF). This subgrid model is developed by parameterizing flame statistics from the LEM-CF sub-model in terms of a reduced set of variables. A database of closure statistics for LES transport equations for these variables is then generated. The run-time application of the model within LES retrieves the closure statistics from the database resulting in a computationally efficient formulation. One key feature of this formulation is that it includes the LEM-CF prediction of turbulent flame extinction limits to develop a localized extinction criterion for the LES. This extinction criterion is a function of the LES resolved scale strain rate which may be directly computed from the LES resolved scale velocity field. The model's capabilities for capturing strain rate and local extinction effects were assessed through its application to the Sandia piloted partially premixed CH 4 /air-air jet flame series. A comparison of model predictions for scalar means and RMS fluctuations for Flame D and F of this series showed good overall agreement with the experimental data. This included good predictions of the temperature and product species in the neck region of Flame F which is dominated by local extinction effects. The model was also applied to determine the blow-out jet bulk velocity for this configuration which was found to be in reasonable agreement with what is available from the experiment. Through this blow-out assessment, three flame modes for this configuration are also identified beyond the Flame F condition. The flame dynamics of a highly oscillating flame mode just prior to blow-out were also investigated. I. IntroductionFluid dynamic strain effects in nonpremixed, partially premixed, and premixed flows play an important role in the evolutionary development and stabilization of flame structure in both commercial and military gas turbine systems. For commercial combustors, the operation at lean conditions for the sake of efficiency and pollutant suppression results in an enhanced susceptibility of the flame to strain rate effects that may lead to local extinction, instability and blow-off. For military systems, the high strain rate environment within high performance gas turbine augmentors results in difficultly in establishing flame stability over the entire flight envelop. For these extreme conditions, experimental correlations are inadequate at establishing the operational limits of these systems. As a result, many gas turbine manufacturers are turning to computational techniques such as large eddy simulation (LES) to assess sub-system performance and to aid in hardware design and modification. However, this approach is limited by the accuracy of sub-models for turbulence-chemistry interactions that are employed. These sub-models play a critical role in establishing the accuracy of the prediction of turbulent extinction limits that affect flame s...

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Turbulence Resolution Scale Dependence in Large-Eddy Simulations of a Jet Flame

Cited by 16 publications

References 44 publications

Large-Eddy Simulation of Premixed Combustion in the Corrugated-Flamelet Regime

Large-Eddy Simulation of Premixed Combustion in the Corrugated-Flamelet Regime

Concentration Fluctuations from Localized Atmospheric Releases

Strain Effects in Partially Premixed Methane-air Jet Flames

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