Turbulent Reynolds number dependence of flame surface density transport in the context of Reynolds averaged Navier–Stokes simulations

2013 ◽  
Vol 34 (1) ◽  
pp. 1347-1356 ◽  
Author(s):  
Nilanjan Chakraborty ◽  
R.S. Cant
Keyword(s):  
Reynolds Number ◽  
Surface Density ◽  
Navier Stokes ◽  
Flame Surface ◽  
Flame Surface Density ◽  
Turbulent Reynolds Number ◽  
Reynolds Averaged Navier Stokes ◽  
Reynolds Number Dependence

scholarly journals Effects of Turbulent Reynolds Number on the Performance of Algebraic Flame Surface Density Models for Large Eddy Simulation in the Thin Reaction Zones Regime: A Direct Numerical Simulation Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mohit Katragadda ◽  
Nilanjan Chakraborty ◽  
R. S. Cant
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Fractal Dimension ◽  
Direct Numerical Simulation ◽  
Surface Density ◽  
Flame Surface ◽  
Algebraic Models ◽  
Flame Surface Density ◽  
Turbulent Reynolds Number ◽  
Reaction Zones

A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame surface density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Rethas been varied by modifying the Karlovitz number Ka and the Damköhler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Retand Ka before reaching an asymptotic value for large values of Retand Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thicknessηi/δzdoes not exhibit any significant dependence on Retfor the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.

scholarly journals Effects of Turbulent Reynolds Number on the Displacement Speed Statistics in the Thin Reaction Zones Regime of Turbulent Premixed Combustion

2011 ◽  
Vol 2011 ◽  
pp. 1-19 ◽  
Author(s):  
Nilanjan Chakraborty ◽  
Markus Klein ◽  
R. S. Cant
Keyword(s):  
Reynolds Number ◽  
Strain Rate ◽  
Surface Density ◽  
Three Dimensional ◽  
Flame Surface ◽  
Tangential Strain ◽  
Turbulent Reynolds Number ◽  
Qualitative Nature ◽  
Displacement Speed ◽  
Turbulent Premixed

The effects of turbulent Reynolds number on the statistical behaviour of the displacement speed have been studied using three-dimensional Direct Numerical Simulation of statistically planar turbulent premixed flames. The probability of finding negative values of the displacement speed is found to increase with increasing turbulent Reynolds number when the Damköhler number is held constant. It has been shown that the statistical behaviour of the Surface Density Function, and its strain rate and curvature dependence, plays a key role in determining the response of the different components of displacement speed. Increasing the turbulent Reynolds number is shown to reduce the strength of the correlations between tangential strain rate and dilatation rate with curvature, although the qualitative nature of the correlations remains unaffected. The dependence of displacement speed on strain rate and curvature is found to weaken with increasing turbulent Reynolds number when either Damköhler or Karlovitz number is held constant, but the qualitative nature of the correlation remains unaltered. The implications of turbulent Reynolds number effects in the context of Flame Surface Density (FSD) modelling have also been addressed, with emphasis on the influence of displacement speed on the curvature and propagation terms in the FSD balance equation.

Development of a RANS Premixed Turbulent Combustion Model Based on the Algebraic Flame Surface Density Concept

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Usman Allauddin ◽  
Michael Pfitzner
Keyword(s):  
Experimental Data ◽  
Surface Density ◽  
Turbulent Flame ◽  
Theoretical Models ◽  
Elevated Pressure ◽  
Navier Stokes ◽  
Combustion Model ◽  
Flame Surface ◽  
Flame Surface Density ◽  
Premixed Turbulent Combustion

Recently, a fractal-based algebraic flame surface density (FSD) premixed combustion model has been derived and validated in the context of large eddy simulation (LES). The fractal parameters in the model, namely the cut-off scales and the fractal dimension were derived using theoretical models, experimental and direct numerical simulation (DNS) databases. The model showed good performance in predicting the premixed turbulent flame propagation for low to high Reynold numbers (Re) in ambient as well as elevated pressure conditions. Several LES combustion models have a direct counterpart in the Reynolds-averaged Navier–Stokes (RANS) context. In this work, a RANS version of the aforementioned LES subgrid scale FSD combustion model is developed. The performance of the RANS model is compared with that of the original LES model and validated with the experimental data. It is found that the RANS version of the model shows similarly good agreement with the experimental data.

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