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dc.contributor.authorChakraborty, Nilanjan
dc.contributor.authorKlein, M.
dc.contributor.authorIm, Hong G.
dc.date.accessioned2020-09-07T13:51:34Z
dc.date.available2020-09-07T13:51:34Z
dc.date.issued2020-09-01
dc.date.submitted2019-11-06
dc.identifier.citationChakraborty, N., Klein, M., & Im, H. G. (2020). A comparison of entrainment velocity and displacement speed statistics in different regimes of turbulent premixed combustion. Proceedings of the Combustion Institute. doi:10.1016/j.proci.2020.06.241
dc.identifier.issn1540-7489
dc.identifier.doi10.1016/j.proci.2020.06.241
dc.identifier.urihttp://hdl.handle.net/10754/664997
dc.description.abstractThe statistics of entrainment velocity, defined as the displacement speed of an enstrophy isosurface, which can be taken to be the interface between turbulent/non-turbulent regions, have been analysed using a Direct Numerical Simulation database of statistically planar H2-air flames with a range of different Karlovitz numbers. It has been found that the component of the entrainment velocity arising from molecular dissipation plays a leading order role for all values of Karlovitz number, whereas the relative importance of the baroclinic torque and dilatation rate weakens with increasing Karlovitz number. By contrast, the relative contribution of the entrainment velocity component arising from vortex-stretching strengthens with increasing Karlovitz number Ka. The mean entrainment velocity remains positive for the case representing the corrugated flamelets regime (i.e. Ka < 1), whereas it assumes negative values in the cases with large values of Karlovitz number (i.e. Ka ≫ 1). The magnitude of the ratio of the mean values of entrainment velocity to the mean values of flame displacement speed conditional upon non-dimensional temperature within the flame front remains of the order of unity irrespective of Karlovitz number. However, the probability density functions of entrainment velocity exhibit considerably higher probabilities of finding large magnitudes than in the case of flame displacement speed. The alignments between the normal vector on the enstrophy isosurface and local principal strain rates have been found to be qualitatively similar to the corresponding alignments between flame normal and local principal strain rates, and the same holds true for the distributions of curvature shape factor of reaction progress variable and enstrophy isosurfaces. These findings indicate that the isosurface topologies and the alignments of normal vectors with local principal strain rates for enstrophy and reaction progress variable exhibit qualitatively similar behaviours. Consequently, turbulence and combustion modelling strategies cannot be considered in isolation in premixed turbulent flames.
dc.description.sponsorshipNC is grateful to EPSRC (EP/K025163/1, EP/R029369/1) and ARCHER for computational support. HGI is grateful to KAUST for research funding and computational support respectively.
dc.publisherElsevier BV
dc.relation.urlhttps://linkinghub.elsevier.com/retrieve/pii/S1540748920303333
dc.rightsNOTICE: this is the author’s version of a work that was accepted for publication in Proceedings of the Combustion Institute. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Proceedings of the Combustion Institute, [, , (2020-09-01)] DOI: 10.1016/j.proci.2020.06.241 . © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.titleA comparison of entrainment velocity and displacement speed statistics in different regimes of turbulent premixed combustion
dc.typeArticle
dc.contributor.departmentClean Combustion Research Center
dc.contributor.departmentComputational Reacting Flow Laboratory (CRFL)
dc.contributor.departmentMechanical Engineering Program
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.identifier.journalProceedings of the Combustion Institute
dc.rights.embargodate2022-09-01
dc.eprint.versionPost-print
dc.contributor.institutionSchool of Engineering, Newcastle University, Claremont Road, Newcastle NE1 7RU, UK.
dc.contributor.institutionDepartment of Aerospace Engineering, Bundeswehr University Munich, LRT1, Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany.
kaust.personIm, Hong G.
dc.date.accepted2020-06-12
refterms.dateFOA2020-09-08T06:53:54Z
dc.date.published-online2020-09-01
dc.date.published-print2020-09


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