The threedimensional structure of swirlswitching in bent pipe flow
Abstract
Swirlswitching is a lowfrequency oscillatory phenomenon which affects the Dean vortices in bent pipes and may cause fatigue in piping systems. Despite thirty years worth of research, the mechanism that causes these oscillations and the frequencies that characterise them remain unclear. In this paper, we show that a threedimensional wavelike structure is responsible for the lowfrequency switching of the dominant Dean vortex. The present study, performed via direct numerical simulation, focuses on the turbulent flow through a $$90^{\circ }$$pipe bend preceded and followed by straight pipe segments. A pipe with curvature 0.3 (defined as ratio between pipe radius and bend radius) is studied for a bulk Reynolds number $$Re=11\,700$$, corresponding to a friction Reynolds number $$Re_{\unicode[STIX]{x1D70F}}\approx 360$$. Synthetic turbulence is generated at the inflow section and used instead of the classical recycling method in order to avoid the interference between recycling and swirlswitching frequencies. The flow field is analysed by threedimensional proper orthogonal decomposition (POD) which for the first time allows the identification of the source of swirlswitching: a wavelike structure that originates in the pipe bend. Contrary to some previous studies, the flow in the upstream pipe does not show any direct influence on the swirlswitching modes. Finally, our analysis further shows that a threedimensional characterisation of the modes is crucial to understand the mechanism, and that reconstructions based on twodimensional POD modes are incomplete.
 Authors:

 KTH Royal Inst. of Technology, Stockholm (Sweden). Linne FLOW Centre. Swedish eScience Research Centre (SeRC). KTH Mechanics
 Argonne National Lab. (ANL), Argonne, IL (United States). Mathematics and Computer Science Division
 Publication Date:
 Research Org.:
 Argonne National Lab. (ANL), Argonne, IL (United States); KTH Royal Inst. of Technology, Stockholm (Sweden)
 Sponsoring Org.:
 USDOE Office of Science (SC); Swedish Research Council (VR)
 OSTI Identifier:
 1427509
 Grant/Contract Number:
 AC0206CH11357
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Journal of Fluid Mechanics
 Additional Journal Information:
 Journal Volume: 835; Journal ID: ISSN 00221120
 Publisher:
 Cambridge University Press
 Country of Publication:
 United States
 Language:
 English
 Subject:
 42 ENGINEERING; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; turbulence simulation; pipe flow boundary layer
Citation Formats
Hufnagel, Lorenz, Canton, Jacopo, Örlü, Ramis, Marin, Oana, Merzari, Elia, and Schlatter, Philipp. The threedimensional structure of swirlswitching in bent pipe flow. United States: N. p., 2017.
Web. doi:10.1017/jfm.2017.749.
Hufnagel, Lorenz, Canton, Jacopo, Örlü, Ramis, Marin, Oana, Merzari, Elia, & Schlatter, Philipp. The threedimensional structure of swirlswitching in bent pipe flow. United States. doi:10.1017/jfm.2017.749.
Hufnagel, Lorenz, Canton, Jacopo, Örlü, Ramis, Marin, Oana, Merzari, Elia, and Schlatter, Philipp. Mon .
"The threedimensional structure of swirlswitching in bent pipe flow". United States. doi:10.1017/jfm.2017.749. https://www.osti.gov/servlets/purl/1427509.
@article{osti_1427509,
title = {The threedimensional structure of swirlswitching in bent pipe flow},
author = {Hufnagel, Lorenz and Canton, Jacopo and Örlü, Ramis and Marin, Oana and Merzari, Elia and Schlatter, Philipp},
abstractNote = {Swirlswitching is a lowfrequency oscillatory phenomenon which affects the Dean vortices in bent pipes and may cause fatigue in piping systems. Despite thirty years worth of research, the mechanism that causes these oscillations and the frequencies that characterise them remain unclear. In this paper, we show that a threedimensional wavelike structure is responsible for the lowfrequency switching of the dominant Dean vortex. The present study, performed via direct numerical simulation, focuses on the turbulent flow through a $90^{\circ }$pipe bend preceded and followed by straight pipe segments. A pipe with curvature 0.3 (defined as ratio between pipe radius and bend radius) is studied for a bulk Reynolds number $Re=11\,700$, corresponding to a friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}\approx 360$. Synthetic turbulence is generated at the inflow section and used instead of the classical recycling method in order to avoid the interference between recycling and swirlswitching frequencies. The flow field is analysed by threedimensional proper orthogonal decomposition (POD) which for the first time allows the identification of the source of swirlswitching: a wavelike structure that originates in the pipe bend. Contrary to some previous studies, the flow in the upstream pipe does not show any direct influence on the swirlswitching modes. Finally, our analysis further shows that a threedimensional characterisation of the modes is crucial to understand the mechanism, and that reconstructions based on twodimensional POD modes are incomplete.},
doi = {10.1017/jfm.2017.749},
journal = {Journal of Fluid Mechanics},
number = ,
volume = 835,
place = {United States},
year = {2017},
month = {11}
}
Web of Science
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Works referencing / citing this record:
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 Journal of Visualization, Vol. 22, Issue 4
Effects of geometry on largescale tubeshear exfoliation of graphite to multilayer graphene and nanographite in water
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 Scientific Reports, Vol. 9, Issue 1