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Article

New insight on flow development and two-dimensionality of turbulent channel flows

Authors: Nagib, H.M., Vinuesa, R., Bartrons, B, Muñoz, M, Subashki, G, Suzuki, Y
Document Type: Article
Pubstate: Accepted
Journal: 65th Annual Meeting of the American Physical Society, Division of Fluid Dynamics. 18 November 2012, San Diego, CA, USA.
Volume:   
Year: 2012

Abstract

The experimental conditions required for a turbulent channel flow to be considered fully-developed and nominally two-dimensional remain a challenging objective. Oil film interferometry (OFI) and static pressure measurements were carried out over the range 200 < Re < 800 in an adjustable-geometry channel flow facility. Three-dimensional effects were studied by considering different aspect ratio (AR) configurations, and also by fixing the AR and modifying the hydraulic diameter DH of the section. The conditions at the centerplane of the channel were characterized through the local skin friction from the OFI and the centerline velocity at three different streamwise locations, as well as the wall shear based on the streamwise global pressure gradient. The skin friction obtained from the pressure gradient overestimated the local shear measurements obtained from the OFI, and did not reproduce the same AR-dependence observed with OFI. Differences between the local and global techniques were also reflected in the flow development. Development length of high-aspect-ratio channels scales with the hydraulic diameter of the section, and is around 200 channel full-heights H, much larger than the values of around 100?150 H previously reported in the literature.