On the fractal characteristics of low Damköhler number flames

Chatakonda, Obulesu; Hawkes, Evatt R.; Aspden, A. J.; Kerstein, Alan R.; Kolla, Hemanth; Chen, Jacqueline H.

doi:10.1016/j.combustflame.2013.05.007

Cited by 67 publications

(44 citation statements)

References 68 publications

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“…One DNS data-set modelled ignition of a lean n-heptane/air mixture with thermal stratifications in a constant volume [13] while the other modelled ignition of an iso-octane/air mixture in a similar configuration [14]. Both DNS databases were generated using S3D, a high order, fully explicit finite-difference solver which has been used for many studies [53][54][55][56][57][58][59]. A 58-species and a 99-species reduced chemical mechanism [13,14] were used for the n-heptane and iso-octane cases, respectively.…”

Section: Numerical Methods and Test Cases Studiedmentioning

confidence: 99%

A Comparative Study of Conditional Moment Closure Modelling for Ignition of iso-octane and n-heptane in Thermally Stratified Mixtures

Salehi

Talei

Hawkes

et al. 2015

Flow Turbulence Combust

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Section: Numerical Methods and Test Cases Studiedmentioning

confidence: 99%

A Comparative Study of Conditional Moment Closure Modelling for Ignition of iso-octane and n-heptane in Thermally Stratified Mixtures

Salehi

Talei

Hawkes

et al. 2015

Flow Turbulence Combust

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“…The theoretical analysis (Kerstein, 1988) cannot explicitly consider such flame structures due to flow geometry, and turbulent premixed flames in previous studies (Cintosun et al, 2007;Cohé et al, 2007;Kobayashi and Kawazoe, 2000;Shim et al, 2011) exclude such effect of strong mean shear of ΔU of over 300 m/s. In addition, a recent theoretical study of Chatakonda et al (2013) reported the fractal dimension of 8=3 for low Damköhler number flames. The present results show reasonable agreement with the theoretical studies (Chatakonda et al, 2013;Kerstein, 1988) which lead to 7=3 D 3 8=3.…”

Section: Fractal Characteristicsmentioning

confidence: 99%

“…In addition, a recent theoretical study of Chatakonda et al (2013) reported the fractal dimension of 8=3 for low Damköhler number flames. The present results show reasonable agreement with the theoretical studies (Chatakonda et al, 2013;Kerstein, 1988) which lead to 7=3 D 3 8=3. The fractal dimension in the present DNS could asymptotically approach to 8=3 in the further downstream region.…”

Section: Fractal Characteristicsmentioning

confidence: 99%

A Fractal Dynamic SGS Combustion Model for Large Eddy Simulation of Turbulent Premixed Flames

Hiraoka

Minamoto

Shimura

et al. 2016

Combustion Science and Technology

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Direct numerical simulation of a turbulent hydrogen-air premixed plane jet flame is performed to investigate fractal characteristics and to evaluate the fractal dynamic subgrid scale (FDSGS) combustion model. The DNS results show that the fractal dimension of flame surfaces increases with the downstream distance, and the fractal dimension computed using a 3D box-counting method reaches about 2.54 in the region where turbulence is developed by mean shear. An inner cutoff representation employed in the FDSGS combustion model could be used in large eddy simulations (LES) of complicated combustion problems. Static tests show that the procedure applied in the FDSGS combustion model adequately predicts the fractal dimension, Kolmogorov length scale, and flame surface area despite the presence of strong mean shear. Dynamic model evaluations are also carried out by conducting a series of LES using the FDSGS and other combustion models. In the dynamic tests, the mean temperature distributions and peak positions of variations of a reaction progress variable fluctuation in the transverse direction obtained from the LES with the FDSGS combustion model show good agreement with the filtered DNS fields. The present evaluation also revealed that one of the strengths in the FDSGS combustion modeling approach is that the model does not require SGS turbulent velocity fluctuation, since modeling of this quantity is straightforward for neither homogeneous turbulence nor the turbulent shear flows. ARTICLE HISTORY

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“…DNS of 3D temporally-developing premixed hydrogen plane jet flames with detailed chemistry at two different Damköhler numbers (Da j ), 0.13 and 0.54, have been performed by Hawkes et al [7,40] and Chatakonda et al [42]. The equivalence ratio is 0.7, which is just on the stable side of the neutral diffusive-thermal stability point [43,44].…”

Section: Computational Configurationmentioning

confidence: 99%

One-Dimensional Modeling of Turbulent Premixed Jet Flames - Comparison to DNS

Punati

Wang

Hawkes

et al. 2016

Flow Turbulence Combust

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The one-dimensional turbulence (ODT) model, formulated in an Eulerian reference frame, is applied to a temporally-evolving premixed turbulent hydrogen plane-jet flame and results are compared with direct numerical simulation (DNS) data. This is the first published study to perform direct comparisons of ODT to DNS for premixed flames. The ODT model solves the full set of conservation equations for mass, momentum, energy, and species on a one-dimensional domain corresponding to the transverse jet direction. The effects of turbulent mixing are modeled via a stochastic process, while the full range of diffusivereactive length and time scales are resolved directly on the one-dimensional domain. A detailed chemical mechanism for hydrogen combustion consisting of 9 species and 21 reactions and a mixture-averaged transport model are used (consistent with the DNS). Cases with two different Damköhler numbers are considered and comparisons between the ODT and DNS data are shown with respect to flow dynamics and thermochemistry. The ODT compared favorably with the DNS in terms of the overall entrainment as judged by the streamwise velocity profile and in terms of local flamelet structure as judged by progress-variable conditional reaction and scalar dissipation rates. While the ODT agreed qualitatively with the overall flame evolution, the net fuel consumption rate was somewhat over-predicted for a brief early period and under-predicted later on, leading to an overly long flame burnout time. It was demonstrated that adjusting a parameter controlling the selection of large eddies improved the prediction of the peak fuel consumption rate and overall reaction progress but worsened the prediction of jet entrainment. An analysis of the 1D nature of ODT is presented that suggests the FSD in ODT needs to be much higher than the FSD in Flow Turbulence Combust the DNS in order to achieve the same overall burning rate, suggesting that the FSD is underpredicted by a significant fraction. While the success of the ODT in reproducing many of the salient features of nonpremixed flames has been demonstrated, the current study suggests that improvements are needed when applied to premixed flames. It is also important to note that the DNS required approximately 40 × 10 6 CPU hours while the ODT required approximately 10 3 CPU hours.

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On the fractal characteristics of low Damköhler number flames

Cited by 67 publications

References 68 publications

A Comparative Study of Conditional Moment Closure Modelling for Ignition of iso-octane and n-heptane in Thermally Stratified Mixtures

A Comparative Study of Conditional Moment Closure Modelling for Ignition of iso-octane and n-heptane in Thermally Stratified Mixtures

A Fractal Dynamic SGS Combustion Model for Large Eddy Simulation of Turbulent Premixed Flames

One-Dimensional Modeling of Turbulent Premixed Jet Flames - Comparison to DNS

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