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Article

Turbulent spots in channel flows.

Authors: Henningson, D.S.H., Johansson, A.V.J., Alfredsson, P.H.
Document Type: Article
Pubstate: Published
Journal: J. Eng. Math.
Volume: 28   21-42
Year: 1994

Abstract

A number of investigations into the formation and development of turbulent spots in plane Poiseuille, plane Couette and watertable flows are reviewed. Three main observations are drawn from this work. Firstly, the initial development is associated with the transient growth due to the three-dimensional lift-up effect. Secondly, the spreading and propagation velocities of the different spots are quite similar. Thirdly, the velocity field inside the spots show essentially all the characteristics of fully developed turbulent flow, albeit at low Reynolds numbers. The mechanism behind the rapid spreading of the spots, however, is not yet fully understood, although observations of wave activity, modifications of the surrounding flow field and stability calculations point in the direction of growth by destabilization.