Scaling and collapse of conditional velocity structure functions in turbulent premixed flames

2019 ◽  
Vol 37 (2) ◽  
pp. 2527-2535 ◽  
Author(s):  
Samuel H.R. Whitman ◽  
Colin A.Z. Towery ◽  
Alexei Y. Poludnenko ◽  
Peter E. Hamlington
Keyword(s):  
Velocity Structure ◽  
Premixed Flames ◽  
Structure Functions ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed

scholarly journals Scaling of Second-Order Structure Functions in Turbulent Premixed Flames in the Flamelet Combustion Regime

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 89
Author(s):  
Peter Brearley ◽  
Umair Ahmed ◽  
Nilanjan Chakraborty ◽  
Markus Klein
Keyword(s):  
Structure Function ◽  
Isotropic Turbulence ◽  
Premixed Flames ◽  
Structure Functions ◽  
Separation Distance ◽  
Second Order ◽  
Order Structure ◽  
Turbulent Premixed Flames ◽  
Flame Brush ◽  
Turbulent Premixed

The second-order velocity structure function statistics have been analysed using a DNS database of statistically planar turbulent premixed flames subjected to unburned gas forcing. The flames considered here represent combustion for moderate values of Karlovitz number from the wrinkled flamelets to the thin reaction zones regimes of turbulent premixed combustion. It has been found that the second-order structure functions exhibit the theoretical asymptotic scalings in the dissipative and (relatively short) inertial ranges. However, the constant of proportionality for the theoretical asymptotic variation for the inertial range changes from one case to another, and this value also changes with structure function orientation. The variation of the structure functions for small length scale separation remains proportional to the square of the separation distance. However, the constant of proportionality for the limiting behaviour according to the separation distance square remains significantly different from the theoretical value obtained in isotropic turbulence. The disagreement increases with increasing turbulence intensity. It has been found that turbulent velocity fluctuations within the flame brush remain anisotropic for all cases considered here and this tendency strengthens towards the trailing edge of the flame brush. It indicates that the turbulence models derived based on the assumptions of homogeneous isotropic turbulence may not be fully valid for turbulent premixed flames.

scholarly journals Modelling of Conditional Scalar Dissipation Rate in Turbulent Premixed Combustion

Computation ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 26 ◽  
Author(s):  
Shokri Amzin ◽  
Mariusz Domagała
Keyword(s):  
Dissipation Rate ◽  
Premixed Flames ◽  
Moment Closure ◽  
Navier Stokes ◽  
Scalar Dissipation ◽  
Flame Surface ◽  
Scalar Dissipation Rate ◽  
Turbulent Premixed Flames ◽  
Conditional Moment ◽  
Turbulent Premixed

In turbulent premixed flames, for the mixing at a molecular level of reactants and products on the flame surface, it is crucial to sustain the combustion. This mixing phenomenon is featured by the scalar dissipation rate, which may be broadly defined as the rate of micro-mixing at small scales. This term, which appears in many turbulent combustion methods, includes the Conditional Moment Closure (CMC) and the Probability Density Function (PDF), requires an accurate model. In this study, a mathematical closure for the conditional mean scalar dissipation rate, <Nc|ζ>, in Reynolds, Averaged Navier–Stokes (RANS) context is proposed and tested against two different Direct Numerical Simulation (DNS) databases having different thermochemical and turbulence conditions. These databases consist of lean turbulent premixed V-flames of the CH4-air mixture and stoichiometric turbulent premixed flames of H2-air. The mathematical model has successfully predicted the peak and the typical profile of <Nc|ζ> with the sample space ζ and its prediction was consistent with an earlier study.

Effects of shear inhomogeneities on the structure of turbulent premixed flames

2019 ◽  
Vol 208 ◽  
pp. 63-78 ◽  
Author(s):  
Wu Jin ◽  
Scott A. Steinmetz ◽  
Mrinal Juddoo ◽  
Matthew J. Dunn ◽  
Zuohua Huang ◽  
...  
Keyword(s):  
Premixed Flames ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed

Small Scale Features of Velocity and Scalar Fields in Turbulent Premixed Flames

2008 ◽  
Vol 82 (3) ◽  
pp. 339-358 ◽  
Author(s):  
Arnaud Mura ◽  
Vincent Robin ◽  
Michel Champion ◽  
Tatsuya Hasegawa
Keyword(s):  
Premixed Flames ◽  
Scalar Fields ◽  
Small Scale ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed

Structure and propagation speeds of turbulent premixed flames—A numerical study

1991 ◽  
Vol 83 (1-2) ◽  
pp. 155-173 ◽  
Author(s):  
Sherif H. El Tahry ◽  
Christopher Rutland ◽  
Joel Ferziger
Keyword(s):  
Numerical Study ◽  
Premixed Flames ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed
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