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POD analysis of the turbulent flow downstream a mild and sharp bend
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0001-8127-8124
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-1663-3553
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-1146-3241
2015 (English)In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 56, no 3, article id 57Article in journal (Refereed) Published
Abstract [en]

Time-resolved stereoscopic particle image velocimetry measurements have been taken of the turbulent flow at the exit plane of a mild and a sharp pipe bend. Cross-sectional flow fields were obtained 1, 2 and 3 pipe diameters downstream the bend in order to capture the flow evolution. Proper orthogonal decomposition (POD) was applied in order to identify the underlying vortical patterns and revealed the existence of a single cell spanning the whole cross section as the most dominant structure, while the Dean cells appeared in the next most energetic modes. The results from these investigations, which indicate the origin of the oscillatory motion of the Dean vortices, the so-called swirl switching, were found to agree with those presented by Hell-strom et al. (J Fluid Mech 735: R7, 2013). Furthermore, the effect of a honeycomb, mounted at the bend inlet, on the flow field has been studied by means of statistical and POD analysis in order to test the hypothesis by Sakakibara and Machida (Phys Fluids 24: 041702, 2012), viz. whether the unsteady behaviour of the Dean cells is related to large-scale structures existing upstream the bend. As a consequence of the honeycomb, the Dean vortices do not appear in the mean field, nor in the most energetic modes, which opens possibilities to overcome or at least delay the problem of fatigue in piping systems which can be caused by the swirl switching.

Place, publisher, year, edition, pages
2015. Vol. 56, no 3, article id 57
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-163985DOI: 10.1007/s00348-015-1926-6ISI: 000350688000010Scopus ID: 2-s2.0-84924207311OAI: oai:DiVA.org:kth-163985DiVA, id: diva2:808034
Funder
Swedish Energy Agency
Note

QC 20150427. QC 20160113

Available from: 2015-04-27 Created: 2015-04-13 Last updated: 2024-01-18Bibliographically approved

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Kalpakli Vester, AthanasiaÖrlü, RamisAlfredsson, P. Henrik

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