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Type: Conference paper
Title: Flow topology of rare back flow events and critical points in turbulent channels and toroidal pipes
Author: Chin, C.
Vinuesa, R.
Örlü, R.
Cardesa, J.
Noorani, A.
Schlatter, P.
Chong, M.
Citation: Journal of Physics : Conference Series, 2018 / Jimenez, J. (ed./s), vol.1001, iss.1
Publisher: IOP Science
Issue Date: 2018
Series/Report no.: Journal of Physics Conference Series
ISSN: 1742-6588
Conference Name: Madrid Summer School on Turbulence (29 May 2017 - 30 Jun 2017 : Madrid, Spain)
Editor: Jimenez, J.
Statement of
C. Chin, R. Vinuesa, R. Örlü, J. I. Cardesa, A. Noorani, P. Schlatter, and M. S. Chong
Abstract: A study of the back flow events and critical points in the flow through a toroidal pipe at friction Reynolds number Re τ ≈ 650 is performed and compared with the results in a turbulent channel flow at Re τ ≈ 934. The statistics and topological properties of the back flow events are analysed and discussed. Conditionally-averaged flow fields in the vicinity of the back flow event are obtained, and the results for the torus show a similar streamwise wall-shear stress topology which varies considerably for the spanwise wall-shear stress when compared to the channel flow. The comparison between the toroidal pipe and channel flows also shows fewer back flow events and critical points in the torus. This cannot be solely attributed to differences in Reynolds number, but is a clear effect of the secondary flow present in the toroidal pipe. A possible mechanism is the effect of the secondary flow present in the torus, which convects momentum from the inner to the outer bend through the core of the pipe, and back from the outer to the inner bend through the pipe walls. In the region around the critical points, the skin-friction streamlines and vorticity lines exhibit similar flow characteristics with a node and saddle pair for both flows. These results indicate that back flow events and critical points are genuine features of wall-bounded turbulence, and are not artifacts of specific boundary or inflow conditions in simulations and/or measurement uncertainties in experiments.
Rights: Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
DOI: 10.1088/1742-6596/1001/1/012002
Grant ID: ARC
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Mechanical Engineering conference papers

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