University of Illinois Urbana-Champaign

Statistical evidence of hairpin vortex packets in wall turbulence

Christensen, Kenneth T., Adrian, Ronald J.

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https://hdl.handle.net/2142/112667

Description

Title
Statistical evidence of hairpin vortex packets in wall turbulence
Author(s)
Christensen, Kenneth T., Adrian, Ronald J.
Issue Date
2000-10
Keyword(s)
Particle Image Velocimetry (piv)
Abstract
Statistical analysis of particle image velocimetry (PIV) measurements in the streamwise, wall-normal plane of turbulent channel flow indicates a coherent and robust alignment of hairpin vortices in the outer layer. Previous experimental and computational analyses of instantaneous velocity realizations show that hairpin vortices dominate the organized structure of the outer layer of wall turbulence and appear to align in a consistent manner. The present work reveals that these hairpin packets leave clear footprints in the statistics of the flow, indicating that they are highly-organized and robust. Linear stochastic estimation is used to estimate the conditional average of the velocity field given the presence of a single vortex core centered in the logarithmic layer. Remarkably, this simple estimate provides a vivid picture of multiple swirling motions coherently aligned in the streamwise direction and inclined away from the wall. This is the first statistical evidence that the outer layer of wall turbulence is dominated by a large-scale, coherent organization of hairpin vortices.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 958
  • 2000-6033
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112667
Sponsor(s)/Grant Number(s)
NSF, Air Force Office of Scientific Research
Copyright and License Information
Copyright 2000 Board of Trustees of the University of Illinois

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Technical Reports - Theoretical and Applied Mechanics (TAM) PRIMARY
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.