Effects of combustion heat release on velocity and scalar statistics in turbulent premixed jet flames at low and high Karlovitz numbers

MacArt, Jonathan F.; Grenga, Temistocle; Müeller, Michael E.

doi:10.1016/j.combustflame.2018.01.022

Cited by 56 publications

(22 citation statements)

References 48 publications

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“…Nonetheless, some of the findings outlined here, such as the variations of the kinetic-energy spectra across the flame or the prevailing drainage of SFS kinetic energy by multi-scale energy-transfer mechanisms related to the convective and pressure-gradient transfer terms, are qualitatively ratified by earlier work on a similar configuration using physical-space and Fourier filters (Towery et al 2016;O'Brien et al 2017), even though the exact equivalences between these different approaches are not straightforward to quantify. Aspects worthy of future work to clarify some of these open research questions may include (a) the consideration of wider parameter ranges in the combustion-regime diagram which may enable comparisons and elucidation of more general physical trends in flame energetics, (b) the partition of the physical-space flow field into solenoidal and irrotational components to wavelet-analyse each contribution and isolate the role of thermal expansion in the energy transfer, (c) the incorporation of complex chemical effects that are known to be important for the propagation of realistic turbulent flames and (d) the utilization of different and perhaps more practical flow configurations for turbulent combustion, including effects related to externally applied pressure gradients (Veynante & Poinsot 1997), shear layers (Wang et al 2017;MacArt, Grenga & Mueller 2018) and high-speed compressibility phenomena (Urzay 2018).…”

Section: Discussionmentioning

confidence: 99%

Spatially localized multi-scale energy transfer in turbulent premixed combustion

et al. 2018

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A three-dimensional wavelet multi-resolution analysis of direct numerical simulations of a turbulent premixed flame is performed in order to investigate the spatially localized spectral transfer of kinetic energy across scales in the vicinity of the flame front. A formulation is developed that addresses the compressible spectral dynamics of the kinetic energy in wavelet space. The wavelet basis enables the examination of local energy spectra, along with inter-scale and subfilter-scale (SFS) cumulative energy fluxes across a scale cutoff, all quantities being available either unconditioned or conditioned on the local instantaneous value of the progress variable across the flame brush. The results include the quantification of mean spectral values and associated spatial variabilities. The energy spectra undergo, in most locations in the flame brush, a precipitous drop that starts at scales of the same order as the characteristic flame scale and continues to smaller scales, even though the corresponding decrease of the mean spectra is much more gradual. The mean convective inter-scale flux indicates that convection increases the energy of small scales, although it does so in a non-conservative manner due to the high aspect ratio of the grid, which limits the maximum scale level that can be used in the wavelet transform, and to the non-periodic boundary conditions, which exchange energy through surface forces, as explicitly elucidated by the formulation. The mean pressure-gradient inter-scale flux extracts energy from intermediate scales of the same order as the characteristic flame scale, and injects energy in the smaller and larger scales. The local SFS-cumulative contribution of the convective and pressure-gradient mechanisms of energy transfer across a given cutoff scale imposed by a wavelet filter is analysed. The local SFS-cumulative energy flux is such that the subfilter scales upstream from the flame always receive energy on average. Conversely, within the flame brush, energy is drained on average from the subfilter scales by convective and pressure-gradient effects most intensely when the filter cutoff is larger than the characteristic flame scale.

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Section: Discussionmentioning

confidence: 99%

Spatially localized multi-scale energy transfer in turbulent premixed combustion

et al. 2018

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“…The same physical explanations which were mentioned earlier in the context of RANS to explain the greater extent of isotropy for T ij and ε ij for the cases with high turbulence intensities are also qualitatively valid in the context of subgrid quantities. The modification of anisotropy distribution in the Lumley triangle in turbulent premixed flames in comparison to that in the corresponding non-reacting flow has been reported in [15], and these findings have, in the meantime, been confirmed independently by a few other DNS groups [37][38][39]: Turbulent premixed flames cause strong anisotropies such that the turbulent state is located on the axisymmetric expansion border and reaches, depending on the turbulence intensity (Karlovitz number), from the isotropic state twothirds up the way to the one component endpoint. Furthermore, early measurements of the enhancement of turbulence anisotropy in large-scale, low-intensity turbulent premixed propane-air flames using two-component measurements have been reported by Furukuwa et al [40].…”

Section: Resultsmentioning

confidence: 60%

Multiscale Analysis of Anisotropy of Reynolds Stresses, Subgrid Stresses and Dissipation in Statistically Planar Turbulent Premixed Flames

et al. 2022

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The characterisation of small-scale turbulence has been an active area of research for decades and this includes, particularly, the analysis of small-scale isotropy, as postulated by Kolmogorov. In particular, the question if the dissipation tensor is isotropic or not, and how it is related to the anisotropy of the Reynolds stresses is of particular interest for modelling purposes. While this subject has been extensively studied in the context of isothermal flows, the situation is more complicated in turbulent reacting flows because of heat release. Furthermore, the landscape of Computational Fluid Dynamics is characterised by a multitude of methods ranging from Reynolds-averaged to Large Eddy Simulation techniques, and they address different ranges of scales of the turbulence kinetic energy spectrum. Therefore, a multiscale analysis of the anisotropies of Reynolds stress, dissipation and sub-grid scale tensor has been performed by using a DNS database of statistically planar turbulent premixed flames. Results show that the coupling between dissipation tensor and Reynolds stress tensor is weaker compared to isothermal turbulent boundary layer flows. In particular, for low and moderate turbulence intensities, heat release induces pronounced anisotropies which affect not only fluctuation strengths but also the characteristic size of structures associated with different velocity components.

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“…A similar criterion of importance of thermal expansion effects in premixed turbulent flames was proposed earlier by Bilger, 72 but based on a different reasoning. Recent DNS data by MacArt et al 73,74 are also consistent with such a criterion, while dilatational and solenoidal dissipations are not compared in the cited papers.…”

Section: B a Simple Criterion To Estimate Importance Of Dilatational Dissipationmentioning

confidence: 90%

Dissipation and dilatation rates in premixed turbulent flames

et al. 2021

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Effects of combustion heat release on velocity and scalar statistics in turbulent premixed jet flames at low and high Karlovitz numbers

Cited by 56 publications

References 48 publications

Spatially localized multi-scale energy transfer in turbulent premixed combustion

Spatially localized multi-scale energy transfer in turbulent premixed combustion

Multiscale Analysis of Anisotropy of Reynolds Stresses, Subgrid Stresses and Dissipation in Statistically Planar Turbulent Premixed Flames

Dissipation and dilatation rates in premixed turbulent flames

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