Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Characterization of the secondary flow in hexagonal ducts
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0001-6570-5499
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0001-9627-5903
2016 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 28, no 12, article id 125101Article in journal (Refereed) Published
Abstract [en]

In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Re-tau,Re- c similar or equal to 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flow integrated over the cross-sectional area < K >(yz) decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress (uw) over bar on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120 degrees aperture of its vertex, whereas in the square duct the 90 degrees corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15D(H) measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90 degrees corner sets the location of a high-speed streak at a distance z(nu)(+) similar or equal to 50 from it, whereas in hexagons the 120 degrees aperture leads to a shorter distance of z(nu)(+) similar or equal to 38. At these locations the root mean square of the wall-shear stresses exhibits an inflection point, which further shows the connections between the near-wall structures and the large-scale motions in the outer flow. Published by AIP Publishing.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016. Vol. 28, no 12, article id 125101
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-201259DOI: 10.1063/1.4968844ISI: 000392092300024Scopus ID: 2-s2.0-85003728125OAI: oai:DiVA.org:kth-201259DiVA, id: diva2:1074312
Note

QC 20170215

Available from: 2017-02-15 Created: 2017-02-15 Last updated: 2017-11-29Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Vinuesa, RicardoSchlatter, Philipp

Search in DiVA

By author/editor
Vinuesa, RicardoSchlatter, Philipp
By organisation
Linné Flow Center, FLOWMechanics
In the same journal
Physics of fluids
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 7 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf