scholarly journals Evolutions of strain rate and dissipation rate of kinetic energy in turbulent premixed flames

2021 ◽  
Vol 33 (12) ◽  
pp. 125132
Author(s):  
Nilanjan Chakraborty ◽  
Christian Kasten ◽  
Umair Ahmed ◽  
Markus Klein
Keyword(s):  
Kinetic Energy ◽  
Strain Rate ◽  
Dissipation Rate ◽  
Premixed Flames ◽  
Turbulent Premixed Flames ◽  
Turbulent Premixed

scholarly journals Local Strain Rate and Curvature Dependences of Scalar Dissipation Rate Transport in Turbulent Premixed Flames: A Direct Numerical Simulation Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-29 ◽  
Author(s):  
Y. Gao ◽  
N. Chakraborty ◽  
N. Swaminathan
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Strain Rate ◽  
Dissipation Rate ◽  
Premixed Flames ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Turbulent Premixed Flames ◽  
The Mean ◽  
Turbulent Premixed

The statistical behaviours of the instantaneous scalar dissipation rateNcof reaction progress variablecin turbulent premixed flames have been analysed based on three-dimensional direct numerical simulation data of freely propagating statistically planar flame and V-flame configurations with different turbulent Reynolds numberRet. The statistical behaviours ofNcand different terms of its transport equation for planar and V-flames are found to be qualitatively similar. The mean contribution of the density-variation termT1is positive, whereas the molecular dissipation term(-D2)acts as a leading order sink. The mean contribution of the strain rate termT2is predominantly negative for the cases considered here. The mean reaction rate contributionT3is positive (negative) towards the unburned (burned) gas side of the flame, whereas the mean contribution of the diffusivity gradient term(D)assumes negative (positive) values towards the unburned (burned) gas side. The local statistical behaviours ofNc,T1,T2,T3,(-D2), andf(D)have been analysed in terms of their marginal probability density functions (pdfs) and their joint pdfs with local tangential strain rateaTand curvaturekm. Detailed physical explanations have been provided for the observed behaviour.

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.

Principal strain rate evolution within turbulent premixed flames for different combustion regimes

2021 ◽  
Vol 33 (1) ◽  
pp. 015111
Author(s):  
Christian Kasten ◽  
Umair Ahmed ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Strain Rate ◽  
Premixed Flames ◽  
Principal Strain ◽  
Turbulent Premixed Flames ◽  
Combustion Regimes ◽  
Turbulent Premixed
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