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Marginally turbulent flow in a square duct

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Uhlmann, Markus and Pinelli, Alfredo and Kawahara, Genta and Sekimoto, Atshushi (2007) Marginally turbulent flow in a square duct. Journal of fluid mechanics, 588 . pp. 153-162. ISSN 0022-1120

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Official URL: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1346008




Abstract

A direct numerical simulation of turbulent flow in a straight square duct was performed in order to determine the minimal requirements for self-sustaining turbulence. It was found that turbulence can be maintained for values of the bulk Reynolds number above approximately 1100, corresponding to a friction-velocity-based Reynolds number of 80. The minimum value for the streamwise period of the computational domain is around 190 wall units, roughly independently of the Reynolds number. We present a characterization of the flow state at marginal Reynolds numbers which substantially differs from the fully turbulent one: the marginal state exhibits a four-vortex secondary flow structure alternating in time whereas the fully turbulent one presents the usual eight-vortex pattern. It is shown that in the regime of marginal Reynolds numbers buffer-layer coherent structures play a crucial role in the appearance of secondary flow of Prandtl's second kind.


Item Type:Article
Uncontrolled Keywords:Near-wall turbulence; numerical-simulation; rectangular duct; transition; vortices; solvers
Subjects:Sciences > Physics
ID Code:21860
Deposited On:14 Jun 2013 10:43
Last Modified:12 Dec 2018 15:07

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