scholarly journals Scalar dissipation rate statistics in turbulent swirling jets

2016 ◽  
Vol 28 (7) ◽  
pp. 075104 ◽  
Author(s):  
V. Stetsyuk ◽  
N. Soulopoulos ◽  
Y. Hardalupas ◽  
A. M. K. P. Taylor
Keyword(s):  
Dissipation Rate ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Swirling Jets

scholarly journals Correlation between small-scale velocity and scalar fluctuations in a turbulent channel flow

2009 ◽  
Vol 627 ◽  
pp. 1-32 ◽  
Author(s):  
HIROYUKI ABE ◽  
ROBERT ANTHONY ANTONIA ◽  
HIROSHI KAWAMURA
Keyword(s):  
Strain Rate ◽  
Channel Flow ◽  
Dissipation Rate ◽  
Compressive Strain ◽  
Outer Region ◽  
Turbulent Channel Flow ◽  
Scalar Fields ◽  
Scalar Dissipation ◽  
Small Scale ◽  
Scalar Dissipation Rate

Direct numerical simulations of a turbulent channel flow with passive scalar transport are used to examine the relationship between small-scale velocity and scalar fields. The Reynolds number based on the friction velocity and the channel half-width is equal to 180, 395 and 640, and the molecular Prandtl number is 0.71. The focus is on the interrelationship between the components of the vorticity vector and those of the scalar derivative vector. Near the wall, there is close similarity between different components of the two vectors due to the almost perfect correspondence between the momentum and thermal streaks. With increasing distance from the wall, the magnitudes of the correlations become smaller but remain non-negligible everywhere in the channel owing to the presence of internal shear and scalar layers in the inner region and the backs of the large-scale motions in the outer region. The topology of the scalar dissipation rate, which is important for small-scale scalar mixing, is shown to be associated with the organized structures. The most preferential orientation of the scalar dissipation rate is the direction of the mean strain rate near the wall and that of the fluctuating compressive strain rate in the outer region. The latter region has many characteristics in common with several turbulent flows; viz. the dominant structures are sheetlike in form and better correlated with the energy dissipation rate than the enstrophy.

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.

scholarly journals Large Eddy Simulations of a turbulent premixed swirl flame using an algebraic scalar dissipation rate closure

2015 ◽  
Vol 162 (9) ◽  
pp. 3180-3196 ◽  
Author(s):  
David Butz ◽  
Yuan Gao ◽  
Andreas M. Kempf ◽  
Nilanjan Chakraborty
Keyword(s):  
Dissipation Rate ◽  
Large Eddy Simulations ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Large Eddy ◽  
Swirl Flame ◽  
Turbulent Premixed

scholarly journals Scalar dissipation rate transport conditional on flow topologies in different regimes of premixed turbulent combustion

2019 ◽  
Vol 37 (2) ◽  
pp. 2353-2361 ◽  
Author(s):  
Nilanjan Chakraborty ◽  
Daniel H. Wacks ◽  
Sebastian Ketterl ◽  
Markus Klein ◽  
Hong G. Im
Keyword(s):  
Turbulent Combustion ◽  
Dissipation Rate ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Premixed Turbulent Combustion

scholarly journals A-Priori Validation of Scalar Dissipation Rate Models for Turbulent Non-Premixed Flames

2020 ◽  
Author(s):  
M. P. Sitte ◽  
C. Turquand d’Auzay ◽  
A. Giusti ◽  
E. Mastorakos ◽  
N. Chakraborty
Keyword(s):  
Dissipation Rate ◽  
A Priori ◽  
Turbulent Flames ◽  
Large Eddy Simulations ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Combustion Model ◽  
Scalar Dissipation Rate ◽  
Jet Flame ◽  
Large Eddy

Abstract The modelling of scalar dissipation rate in conditional methods for large-eddy simulations is investigated based on a priori direct numerical simulation analysis using a dataset representing an igniting non-premixed planar jet flame. The main objective is to provide a comprehensive assessment of models typically used for large-eddy simulations of non-premixed turbulent flames with the Conditional Moment Closure combustion model. The linear relaxation model gives a good estimate of the Favre-filtered scalar dissipation rate throughout the ignition with a value of the related constant close to the one deduced from theoretical arguments. Such value of the constant is one order of magnitude higher than typical values used in Reynolds-averaged approaches. The amplitude mapping closure model provides a satisfactory estimate of the conditionally filtered scalar dissipation rate even in flows characterised by shear driven turbulence and strong density variation.

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