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ID 51063
file
creator
Oki, Junichi
Kuga, Yukika
Yamamoto, Ryo
Nakamura, Kazuhiro
Yokohata, Hideaki
subject
Turbulence
Pulsatile flow
Secondary flow
Particle image velocimetry
Swirl switching
abstract
We investigate turbulent flow with highly pulsating axial velocity passing through a duct with both first and second bends. The time-dependent velocity fields downstream of the bends were measured using time-resolved stereo particle image velocimetry for the steady case (Reynolds number Re = 36,700) and the pulsatile case (Re = 37,800 and Womersley number α = 59.1). Proper orthogonal decomposition (POD) of the in-plane velocity data isolates the energetic structures of the secondary flow. The modes downstream of the first bend have a Dean motion (mode 0), single swirl (mode 1), and double swirl (mode 2), which agree with those of previous studies on steady turbulent flow. Downstream of the second bend, additional vortices appear in the modes owing to the secondary flow originating in the first bend. The modal structure of the pulsatile case is virtually the same as that of the steady case. To our knowledge, we are the first to find swirl switching in pulsatile flow, whereas the switching has been reported only for steady cases. We further conduct a time-frequency analysis via wavelet transformation onto the POD time coefficient, showing intermittency in energy of the mode associated with swirl switching.
description
This work was partially supported by a research grant from The Hiroshima University Education and Research Support Foundation.
journal title
Flow, Turbulence and Combustion
volume
Volume 104
start page
817
end page
833
date of issued
2020-04
publisher
Springer
issn
1386-6184
1573-1987
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
This is a post-peer-review, pre-copyedit version of an article published in Flow, Turbulence and Combustion. The final authenticated version is available online at: https://doi.org/10.1007/s10494-019-00088-y.
This is not the published version. Please cite only the published version. この論文は出版社版ではありません。引用の際には出版社版をご確認、ご利用ください。
relation url
department
Graduate School of Advanced Science and Engineering