Modelling of the Curvature Term in the Flame Surface Density Transport Equation: A Direct Numerical Simulations Based Analysis

A Direct Numerical Simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with Lewis numbersLeranging from 0.34 to 1.2 has been used to analyse the statistical behaviours of the curvature term of the generalised Flame surface Density (FSD) transport equation, in the context of the Large Eddy Simulation (LES). Lewis number is shown to have significant influences on the statistical behaviours of the resolved and sub-grid parts of the FSD curvature term. It has been found that the existing models for the sub-grid curvature termCsgdo not capture the qualitative behaviour of this term extracted from the DNS database for flames withLe<<1. The existing models ofCsgonly predict negative values, whereas the sub-grid curvature term is shown to assume positive values within the flame brush for theLe=0.34and 0.6 flames. Here the sub-grid curvature terms arising from combined reaction and normal diffusion and tangential diffusion components of displacement speed are individually modelled, and the new model of the sub-grid curvature term has been found to captureCsgextracted from DNS data satisfactorily for all the different Lewis number flames considered here for a wide range of filter widths.

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Direct numerical simulations analysis of flame surface density models for nonpremixed turbulent combustion

Physics of Fluids ◽

10.1063/1.869753 ◽

1998 ◽

Vol 10 (9) ◽

pp. 2347-2368 ◽

Cited By ~ 22

Author(s):

Eric Van Kalmthout ◽

Denis Veynante

Keyword(s):

Numerical Simulations ◽

Turbulent Combustion ◽

Surface Density ◽

Direct Numerical Simulations ◽

Flame Surface ◽

Flame Surface Density

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Modelling of the Curvature Term of the Flame Surface Density Transport Equation for Large Eddy Simulations

Journal of Combustion ◽

10.1155/2012/915482 ◽

2012 ◽

Vol 2012 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Mohit Katragadda ◽

Nilanjan Chakraborty

Keyword(s):

Transport Equation ◽

Surface Density ◽

Flame Surface ◽

Flame Surface Density ◽

New Model ◽

Curvature Term ◽

Large Eddy ◽

Diffusion Component ◽

Normal Diffusion ◽

Displacement Speed

A simplified chemistry based three-dimensional Direct Numerical Simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different values of turbulent Reynolds number has been used for the a priori modelling of the curvature term of the generalised Flame Surface Density (FSD) transport equation in the context of Large Eddy Simulation (LES). The curvature term has been split into the contributions arising due to the reaction and normal diffusion components of displacement speed and the term originating from the tangential diffusion component of displacement speed. Subsequently, these contributions of the curvature term have been split into the resolved and subgrid contributions. New models have been proposed for the subgrid curvature terms arising from the combined reaction and normal diffusion components and the tangential diffusion component of displacement speed. The performances of the new model and the existing models for the subgrid curvature term have been compared with the corresponding quantity extracted from the explicitly filtered DNS data. The new model for the subgrid curvature term is shown to perform satisfactorily in all cases considered in the current study, accounting for wide variations in LES filter size.

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A priori analysis of the curvature and propagation terms of the flame surface density transport equation for large eddy simulation

Physics of Fluids ◽

10.1063/1.2772326 ◽

2007 ◽

Vol 19 (10) ◽

pp. 105101 ◽

Cited By ~ 63

Author(s):

Nilanjan Chakraborty ◽

R. S. Cant

Keyword(s):

Large Eddy Simulation ◽

Transport Equation ◽

Surface Density ◽

A Priori ◽

Flame Surface ◽

Flame Surface Density ◽

Eddy Simulation ◽

Large Eddy ◽

A Priori Analysis

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Turbulent Premixed LES Combustion Models Based on Fractal Flame Surface Density Concepts

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2014-25919 ◽

2014 ◽

Cited By ~ 1

Author(s):

Usman Allauddin ◽

Roman Keppeler ◽

Michael Pfitzner

Keyword(s):

Numerical Simulations ◽

Gas Turbines ◽

Surface Density ◽

Original Model ◽

Premixed Combustion ◽

Flame Surface ◽

Flame Surface Density ◽

Combustion Models ◽

Fractal Characteristics ◽

Turbulent Premixed

With increasing computational power, Large Eddy Simulation (LES) is being widely used to study and develop a better understanding of turbulent combustion. A variety of subgrid combustion models have been proposed to investigate premixed combustion in LES. One of the physical aspects that can be exploited, are the fractal characteristics of premixed flames which have been confirmed in several experimental works. In this work the performance of a simplified version of an already established sub-grid flame surface density combustion model, which is based on the fractal characteristics of the flame surface is investigated. The original model was derived on the basis of theoretical models, experimental and direct numerical simulations databases and its performance was validated with data from the available literature. The simplifications to the established flame surface density model are discussed, and its performance is validated in comparison to the original model. Secondly numerical simulations with both models at conditions typical for spark-ignition engines and industrial gas turbines are validated against experimental data. It is found that both original and simplified models are suitable for LES of low to high turbulent premixed combustion in ambient and elevated pressure conditions.

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