# Tomographic PIV measurements of a regenerating hairpin vortex

Tomographic PIV measurements of a regenerating hairpin vortex The three-dimensional formation and regeneration of a hairpin vortex in a laminar boundary layer is studied in a free-surface water channel. The vortex is generated by fluid injection through a narrow slot into a laminar boundary layer $$(Re_{\delta ^*} = 485)$$ ( R e δ ∗ = 485 ) and recorded with tomographic particle image velocimetry. The swirling strength based on the $$\lambda _2$$ λ 2 criterion shows that the hairpin initially forms at the upstream edge of the elongated ring vortex produced by the injection. The elongated ring vortex decays while the hairpin vortex strengthens. Because the hairpin vortex is of sufficient strength, it forms a kink in the legs as a result of inviscid induction. A bridging structure forms between the legs initially upstream of the kink. As this structure dissipates, another bridging structure forms downstream of the kink and closes the vortex loop between the legs. This pinches off the original hairpin head such that two distinct vortices result. The formation of the secondary hairpin head does not appear to be preceded by a reduction in the spanwise gap between the legs or significant change in height above the wall as has been seen when exposed to a mean turbulent profile. Instead, the formation is preceded by the stretching of the hairpin legs downstream of the kink, exposes the ejected fluid between the legs to boundary layer flow producing conditions similar to those that formed the initial hairpin vortex. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

# Tomographic PIV measurements of a regenerating hairpin vortex

, Volume 57 (1) – Dec 14, 2015
13 pages

/lp/springer_journal/tomographic-piv-measurements-of-a-regenerating-hairpin-vortex-DYFdm7qIbG
Publisher
Springer Berlin Heidelberg
Copyright © 2015 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-015-2089-1
Publisher site
See Article on Publisher Site

## You’re reading a free preview. Subscribe to read the entire article.

### DeepDyve is your personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month ### Explore the DeepDyve Library ### Unlimited reading Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere. ### Stay up to date Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates. ### Organize your research It’s easy to organize your research with our built-in tools. ### Your journals are on DeepDyve Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more. All the latest content is available, no embargo periods. ### Monthly Plan • Read unlimited articles • Personalized recommendations • No expiration • Print 20 pages per month • 20% off on PDF purchases • Organize your research • Get updates on your journals and topic searches$49/month

14-day Free Trial

Best Deal — 39% off

### Annual Plan

• All the features of the Professional Plan, but for 39% off!
• Billed annually
• No expiration
• For the normal price of 10 articles elsewhere, you get one full year of unlimited access to articles.

$588$360/year

billed annually

14-day Free Trial