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Temporal acceleration of a turbulent channel flow

Seddighi, M (2017) Temporal acceleration of a turbulent channel flow. Journal of Fluid Mechanics, 835. pp. 471-490. ISSN 0022-1120

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Abstract

We report new laboratory experiments of a flow accelerating from an initially turbulent state following the opening of a valve, together with large eddy simulations of the experiments and extended Stokes first problem solutions for the early stages of the flow. The results show that the transient flow closely resembles an accelerating laminar flow superimposed on the original steady turbulent flow. The primary consequence of the acceleration is the temporal growth of a boundary layer from the wall, gradually leading to a strong instability causing transition. This extends the findings of previous direct numerical simulations of transient flow following a near-step increase in flow rate. In this interpretation, the initial turbulence is not the primary characteristic of the resulting transient flow, but can be regarded as noise, the evolution of which is strongly influenced by the development of the boundary layer. We observe the spontaneous appearance of turbulent spots and discontinuities in the velocity signals in time and space, revealing rich detail of the transition process, including a striking contrast between streamwise and wall-normal fluctuating velocities.

Item Type: Article
Uncontrolled Keywords: 01 Mathematical Sciences, 09 Engineering
Subjects: T Technology > TJ Mechanical engineering and machinery
Divisions: Maritime and Mechanical Engineering
Publisher: Cambridge University Press (CUP)
Date Deposited: 16 Oct 2017 10:12
Last Modified: 06 Mar 2018 10:09
Editors: Mathur, A, Gorji, S, He, S, Vardy, AE, O'Donoghue, T and Pokrajac, D
URI: http://researchonline.ljmu.ac.uk/id/eprint/7356

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