Assessment of subgrid-scale stress statistics in non-premixed turbulent wall-jet flames
(English)Manuscript (preprint) (Other academic)
We investigate the properties of the subgrid-scale (SGS) stress tensor and SGS dissipation of kinetic energy and enstrophy,using the direct numerical simulation (DNS) data of a non-premixed reacting turbulent wall-jet flow, with and without heat release.The separation of scales, to obtain the SGS quantities, is achieved by application of a box filter.This study comprises an analysis on the topology of the resolved strain-rate andSGS stress tensors, through an assessment of their eigenvectors and their relative alignment. To find out the heat-release effects on the dynamics of the turbulent energy dissipation, SGS dissipation of kinetic energy andenstrophy are evaluated using length-scale, probability density functions (PDFs) and mean value analysis.
It is found that the mean SGS shear stress and turbulent kinetic energy are suppressed by the heat release, whilethe SGS anisotropy is substantially increased.Although, the topology of the resolved strain-rate tensor only marginally differs between the isothermal and exothermic cases in the near-wall wall region,substantial differences are observed in the shear layer in the jet area, where the compressibility effects are large andthe exothermic effects are found to promote compression states.The relative alignment between the SGS stress and resolved strain-rate tensors is also affected by the heat release.The mean SGS dissipation of kinetic energy is increased, while the SGS dissipation of enstrophy is decreased by the heat release.Interesting differences in the shape of the PDFs of the SGS dissipation are observed between the isothermal and exothermic cases, such as thechange in the intermittency of both SGS dissipation terms.
Subgrid-scale stress, turbulent wall-jet flow, combustion, heat release
Research subject Engineering Mechanics
IdentifiersURN: urn:nbn:se:kth:diva-160604OAI: oai:DiVA.org:kth-160604DiVA: diva2:790528
QC 201605242015-02-252015-02-252016-05-24Bibliographically approved