Spatial signatures of retrograde spanwise vortices in wall turbulence

Natrajan, Vinay K.; Wu, Yanhua; Christensen, Kenneth T.

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https://hdl.handle.net/2142/344 Copy

Description

Title

Spatial signatures of retrograde spanwise vortices in wall turbulence

Author(s)

• Natrajan, Vinay K.
• Wu, Yanhua
• Christensen, Kenneth T.

Issue Date

2006-04

Keyword(s)

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 Ret = 2350. The present results suggest that a portion of retrograde spanwise vortices have a well-defined spatial relationship with neighboring prograde vortices. Two-point cross-correlations and conditionally averaged velocity fields given a retrograde vortex reveal that such structures are typically oriented either upstream/below or downstream/above a prograde core. While the former preferred orientation is consistent with the typical-eddy patterns reported by Falco and co-workers, we offer an alternative interpretation for a portion of these retrograde/prograde pairs. In particular, the arrangement of a retrograde core upstream and below of 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.

Publisher

Department of Theoretical and Applied Mechanics (UIUC)

Series/Report Name or Number

TAM Reports 1091, (2006)

ISSN

0073-5264

Type of Resource

text

Language

en

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http://hdl.handle.net/2142/344

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