Scale interactions in a mixing layer – the role of the large-scale gradients

Handle URI:
http://hdl.handle.net/10754/621751
Title:
Scale interactions in a mixing layer – the role of the large-scale gradients
Authors:
Fiscaletti, D.; Attili, Antonio; Bisetti, Fabrizio ( 0000-0001-5162-7805 ) ; Elsinga, G. E.
Abstract:
© 2016 Cambridge University Press. The interaction between the large and the small scales of turbulence is investigated in a mixing layer, at a Reynolds number based on the Taylor microscale of , via direct numerical simulations. The analysis is performed in physical space, and the local vorticity root-mean-square (r.m.s.) is taken as a measure of the small-scale activity. It is found that positive large-scale velocity fluctuations correspond to large vorticity r.m.s. on the low-speed side of the mixing layer, whereas, they correspond to low vorticity r.m.s. on the high-speed side. The relationship between large and small scales thus depends on position if the vorticity r.m.s. is correlated with the large-scale velocity fluctuations. On the contrary, the correlation coefficient is nearly constant throughout the mixing layer and close to unity if the vorticity r.m.s. is correlated with the large-scale velocity gradients. Therefore, the small-scale activity appears closely related to large-scale gradients, while the correlation between the small-scale activity and the large-scale velocity fluctuations is shown to reflect a property of the large scales. Furthermore, the vorticity from unfiltered (small scales) and from low pass filtered (large scales) velocity fields tend to be aligned when examined within vortical tubes. These results provide evidence for the so-called 'scale invariance' (Meneveau & Katz, Annu. Rev. Fluid Mech., vol. 32, 2000, pp. 1-32), and suggest that some of the large-scale characteristics are not lost at the small scales, at least at the Reynolds number achieved in the present simulation.
KAUST Department:
Clean Combustion Research Center
Citation:
Fiscaletti D, Attili A, Bisetti F, Elsinga GE (2016) Scale interactions in a mixing layer – the role of the large-scale gradients. Journal of Fluid Mechanics 791: 154–173. Available: http://dx.doi.org/10.1017/jfm.2016.53.
Publisher:
Cambridge University Press (CUP)
Journal:
Journal of Fluid Mechanics
Issue Date:
15-Feb-2016
DOI:
10.1017/jfm.2016.53
Type:
Article
ISSN:
0022-1120; 1469-7645
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorFiscaletti, D.en
dc.contributor.authorAttili, Antonioen
dc.contributor.authorBisetti, Fabrizioen
dc.contributor.authorElsinga, G. E.en
dc.date.accessioned2016-11-03T13:24:10Z-
dc.date.available2016-11-03T13:24:10Z-
dc.date.issued2016-02-15en
dc.identifier.citationFiscaletti D, Attili A, Bisetti F, Elsinga GE (2016) Scale interactions in a mixing layer – the role of the large-scale gradients. Journal of Fluid Mechanics 791: 154–173. Available: http://dx.doi.org/10.1017/jfm.2016.53.en
dc.identifier.issn0022-1120en
dc.identifier.issn1469-7645en
dc.identifier.doi10.1017/jfm.2016.53en
dc.identifier.urihttp://hdl.handle.net/10754/621751-
dc.description.abstract© 2016 Cambridge University Press. The interaction between the large and the small scales of turbulence is investigated in a mixing layer, at a Reynolds number based on the Taylor microscale of , via direct numerical simulations. The analysis is performed in physical space, and the local vorticity root-mean-square (r.m.s.) is taken as a measure of the small-scale activity. It is found that positive large-scale velocity fluctuations correspond to large vorticity r.m.s. on the low-speed side of the mixing layer, whereas, they correspond to low vorticity r.m.s. on the high-speed side. The relationship between large and small scales thus depends on position if the vorticity r.m.s. is correlated with the large-scale velocity fluctuations. On the contrary, the correlation coefficient is nearly constant throughout the mixing layer and close to unity if the vorticity r.m.s. is correlated with the large-scale velocity gradients. Therefore, the small-scale activity appears closely related to large-scale gradients, while the correlation between the small-scale activity and the large-scale velocity fluctuations is shown to reflect a property of the large scales. Furthermore, the vorticity from unfiltered (small scales) and from low pass filtered (large scales) velocity fields tend to be aligned when examined within vortical tubes. These results provide evidence for the so-called 'scale invariance' (Meneveau & Katz, Annu. Rev. Fluid Mech., vol. 32, 2000, pp. 1-32), and suggest that some of the large-scale characteristics are not lost at the small scales, at least at the Reynolds number achieved in the present simulation.en
dc.publisherCambridge University Press (CUP)en
dc.subjectshear layer turbulenceen
dc.subjectturbulence modellingen
dc.subjectturbulent flowsen
dc.titleScale interactions in a mixing layer – the role of the large-scale gradientsen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalJournal of Fluid Mechanicsen
dc.contributor.institutionLaboratory for Aero and Hydrodynamics, Department of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Leeghwaterstraat 21, CA, Delft, Netherlandsen
kaust.authorAttili, Antonioen
kaust.authorBisetti, Fabrizioen
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