A posteriori testing of algebraic flame surface density models for LES

Ma, Terence; Stein, Oliver T.; Chakraborty, Nilanjan; Kempf, Andreas

doi:10.1080/13647830.2013.779388

Cited by 78 publications

(96 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The modelling of this wrinkling factor Ξ can significantly affect the simulation predictions. Several models have previously been proposed [54,55]. The one used in the present study gave the best fit to experimental data, and is based on Fureby's fractal approach [60]:…”

Section: Methodsmentioning

confidence: 99%

“…(5)). In recent papers, some of the more popular algebraic FSD models are assessed in the context of LES based on DNS results or experimental data [54,55]. In the present study, the source term is modelled using:…”

Section: Methodsmentioning

confidence: 99%

“…(8) and (9)), an approximation of the subgrid-scale velocity fluctuation u ′ sgs is required. As in the previous studies [55,62], it is estimated using the relevant LES model: The above FSD combustion model was implemented in Code S aturne. All variables in the code are collocated at the cell centres and the SIMPLEC prediction/correction algorithm is used for pressure-velocity coupling.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Simulation of the flame describing function of a turbulent premixed flame using an open-source LES solver

Han

Morgans

2015

Combustion and Flame

103

View full text Add to dashboard Cite

Numerical simulations were used to characterise the non-linear response of a turbulent premixed flame to acoustic velocity fluctuations. The test flame simulated was the bluff body stabilised flame which has been the subject of a detailed experimental study (Balachandran et al., 2005, Combustion & Flame). Simulations were performed using Large Eddy Simulation (LES) via the open source Computational Fluid Dynamics (CFD) software, Code S aturne, with combustion modelled by combining a Flame Surface Density (FSD) method with a fractal approach for the wrinkling factor. The cold flow field and the unforced reacting flow were used for preliminary code validation. In order to characterise the non-linear response of the unsteady heat release rate to acoustic forcing, a harmonically varying velocity fluctuation, for which both the forcing frequency and normalised forcing amplitude were varied, was imposed. The flame response was characterised via a Flame Describing Function (FDF), also known as a nonlinear flame transfer function, for which the gain and phase shift depend on forcing amplitude as well as forcing frequency. The response at four frequencies was compared to experimental data in detail, confirming that the LES results captured both the qualitative flame dynamics and the quantitative response of the heat release rate with very reasonable accuracy. The full FDF was then obtained across more frequencies, again showing a good fit with the experimental data, other than for a slight under-prediction in gain, most probably due to neglecting the effect of wall heat loss and the effect of combustion modelling. The agreement was significantly better than has been obtained previously for this test case using numerical simulations. Finally, it was found that increasing combustor length had little affect on the flame response, which may prove useful for future long combustor stability and limit cycle analysis. This work thus confirms that LES, in this case via the open source Code S aturne, provides a useful tool for characterising the response of lean premixed turbulent flames.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of the flame describing function of a turbulent premixed flame using an open-source LES solver

Han

Morgans

2015

Combustion and Flame

103

View full text Add to dashboard Cite

show abstract

“…A-priori analysis of both FRDI and SGSF terms individually was reported by the authors in the past [13][14][15]. Recent a-posteriori analyses [16,17] …”

Section: ∂ (ρC) /∂T+∇· (ρũC) = −∇ · (ρUc −ρũC) + ∇ · (ρD∇c) +ω Cmentioning

confidence: 99%

Analysis of the Combined Modelling of Sub-grid Transport and Filtered Flame Propagation for Premixed Turbulent Combustion

Klein

Chakraborty

Pfitzner

2016

Flow Turbulence Combust

Self Cite

View full text Add to dashboard Cite

Flame surface density (FSD) based reaction rate closure is an important methodology of turbulent premixed flame modelling in the context of Large Eddy Simulations (LES). The transport equation for the Favre-filtered reaction progress variable needs closure of the filtered reaction diffusion imbalance (FRDI) term (i.e. filtered value of combined reaction rate and molecular diffusion rate) and the sub-grid scalar flux (SGSF). A-priori analysis of the FRDI and SGSF terms has in the past revealed advantages and disadvantages of the specific modelling attempts. However, it is important to understand the interaction of the FRDI and SGSF closures for a successful implementation of the FSD based closure. Furthermore, it is not known a-priori if the combination of the best SGSF model with the best FRDI model results in the most suitable overall modelling strategy. In order to address this question, a variety of SGSF models is analysed in this work together with one well established and one recent FRDI closure based on a-priori analysis. It is found that the success of the combined FRDI and SGSF closures depends on subtle details like the co-variances of the FRDI and SGSF terms. It is demonstrated that the gradient hypothesis model is not very successful in representing the SGSF term. However the gradient hypothesis provides satisfactory performance in combination of a recently proposed FRDI closure, whereas unsatisfactory results are obtained when used in combination with another existing closure, which was shown to predict the FRDI term satisfactorily in several previous analyses.

show abstract

“…2). In Equation (3), the generalized flame surface R gen is approximated by replacing the Reynolds-averaged progress variable jrcj by the Favre-averaged one jrcj, where the counter gradient transport F cgt is implicitly included (see the Discussion by Ma et al [21]). The two terms _ w c and D in Equation (1) are the mean reaction source term and the molecular diffusivity.…”

Section: Combustion Modeling With Flame Surface Densitymentioning

confidence: 99%

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Nguyen

Kempf

2017

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

View full text Add to dashboard Cite

-This work investigates the influence of numerical dissipation on the modeled combustion in Large Eddy Simulations (LES). It is well known that capturing the dynamics of the in-cylinder flow is crucial for engine simulations, as it strongly affects flame propagation. The flame propagation during the power-stroke highly depends on the turbulence level that is developed throughout compression. This turbulence level will be strongly influenced by the accuracy of the numerical schemes employed. Even a small extent of upwinding, filtering, low-order implicit time-stepping, cell-stretching or mapping between grids may affect the flow field, the turbulence level, and hence the turbulent flame speed and the pressure curve. To provide a reference, the LES in-house code PsiPhi is used, which ensures a minimum of dissipation due to high order explicit time-stepping, homogeneous and isotropic filters and cells. Good stability of the code permits the use of a second-order Central Differencing Scheme (CDS) for the transport of momentum, avoiding numerical dissipation. To analyse the effect of numerical dissipation, simulations of a fired engine are performed using different numerical schemes for the convection of momentum. Physical quantities including the total kinetic energy, the velocity gradient, the turbulent viscosity, the in-cylinder pressure, the flame propagation or the burning rate of different test cases are evaluated and compared to each other to show the numerical effects on combustion. Furthermore, the suitability of common LES quality criteria including an energy criterion and viscosity ratio is discussed based on the comparison of simulations with less and more accurate numerics. It is shown that these LES quality indicators can be highly misleading.

show abstract

A posteriori testing of algebraic flame surface density models for LES

Cited by 78 publications

References 61 publications

Simulation of the flame describing function of a turbulent premixed flame using an open-source LES solver

Simulation of the flame describing function of a turbulent premixed flame using an open-source LES solver

Analysis of the Combined Modelling of Sub-grid Transport and Filtered Flame Propagation for Premixed Turbulent Combustion

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Contact Info

Product

Resources

About