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Title:Spatial signatures of retrograde spanwise vortices in wall turbulence
Author(s):Natrajan, Vinay K.; Wu, Yanhua; Christensen, Kenneth T.
Wall turbulence
Abstract:The spatial signatures of retrograde spanwise vortices in wall turbulence are assessed from particle-image velocimetry measurements in the streamwise–wall-normal plane of a zero-pressure-gradient turbulent boundary layer at Reτ ≡u∗δ/ν =2350. The present results suggest that a proportion of retrograde spanwise vortices have a welldefined spatial relationship with neighbouring prograde vortices. Two-point crosscorrelations and conditionally averaged velocity fields given a retrograde vortex reveal that such structures are typically oriented either upstream of and below or downstream of and above a prograde core. While these pairings are consistent with the typical-eddy patterns reported by Falco and co-workers, we offer an alternative interpretation for a proportion of these retrograde/prograde pairs. In particular, the arrangement of a retrograde spanwise vortex upstream of and below a prograde core is also consistent with the spatial signature revealed if an omega-shaped hairpin structure were sliced through its shoulder region by a fixed streamwise–wall-normal measurement plane.
Issue Date:2007
Publisher:Cambridge University Press
Citation Info:V.K. Natrajan, Y. Wu, and K.T. Christensen. 2007. Spatial signatures of retrograde spanwise vortices in wall turbulence. Journal of Fluid Mechanics. 574: 155–167.
Publication Status:published or submitted for publication
Peer Reviewed:is peer reviewed
Rights Information:Copyright owned by Cambridge University Press 2007.
Date Available in IDEALS:2007-07-24

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