Effect of thickness-to-chord ratio on the wake of two-dimensional rectangular cylinders

Effect of thickness-to-chord ratio on the wake of two-dimensional rectangular cylinders The dynamics of the nearly periodic highly modulated turbulent wakes of two-dimensional rectangular cylinders normal to a uniform flow are investigated experimentally for thickness-to-chord ratios between 0.05 and 1.92 at Reynolds numbers around 6600. Measurements were conducted using planar, time-resolved stereoscopic particle image velocimetry. A generalized phase average analysis, which invokes elements of mean-field theory to relate the temporal modal coefficients of the fundamental harmonic and slow-varying base-flow drift, provided a statistically significant representation of the coherent cycle-to-cycle variation of the shedding process. It is shown that the characteristics of the wake velocity fluctuations change as a function of the thickness-to-chord ratio and can be related to structural differences in the wake topology. Moreover, the trajectory of shed vortices plays an important role in distinguishing the dynamics observed for different fluctuation-amplitude cycles. Based on differences in amplitude modulation characteristics and the vortex formation region topology, three flow regimes can be defined: a thin-plate regime, for which the feedback between forming vortices and base pressure is important; a cylinder-like thick-plate regime for which the obstacle afterbody suppresses the feedback; and a long-plate regime for which wake periodicity is not associated with the classical Kármán shedding process. The present analysis highlights the importance of the feedback mechanism for the thin-plate regime and helps reconcile differences in the reported critical thickness values between regimes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review Fluids American Physical Society (APS)

Effect of thickness-to-chord ratio on the wake of two-dimensional rectangular cylinders

Preview Only

Effect of thickness-to-chord ratio on the wake of two-dimensional rectangular cylinders

Abstract

The dynamics of the nearly periodic highly modulated turbulent wakes of two-dimensional rectangular cylinders normal to a uniform flow are investigated experimentally for thickness-to-chord ratios between 0.05 and 1.92 at Reynolds numbers around 6600. Measurements were conducted using planar, time-resolved stereoscopic particle image velocimetry. A generalized phase average analysis, which invokes elements of mean-field theory to relate the temporal modal coefficients of the fundamental harmonic and slow-varying base-flow drift, provided a statistically significant representation of the coherent cycle-to-cycle variation of the shedding process. It is shown that the characteristics of the wake velocity fluctuations change as a function of the thickness-to-chord ratio and can be related to structural differences in the wake topology. Moreover, the trajectory of shed vortices plays an important role in distinguishing the dynamics observed for different fluctuation-amplitude cycles. Based on differences in amplitude modulation characteristics and the vortex formation region topology, three flow regimes can be defined: a thin-plate regime, for which the feedback between forming vortices and base pressure is important; a cylinder-like thick-plate regime for which the obstacle afterbody suppresses the feedback; and a long-plate regime for which wake periodicity is not associated with the classical Kármán shedding process. The present analysis highlights the importance of the feedback mechanism for the thin-plate regime and helps reconcile differences in the reported critical thickness values between regimes.
Loading next page...
 
/lp/aps_physical/effect-of-thickness-to-chord-ratio-on-the-wake-of-two-dimensional-7MrjgFvFB6
Publisher
The American Physical Society
Copyright
Copyright © ©2017 American Physical Society
eISSN
2469-990X
D.O.I.
10.1103/PhysRevFluids.2.064702
Publisher site
See Article on Publisher Site

Abstract

The dynamics of the nearly periodic highly modulated turbulent wakes of two-dimensional rectangular cylinders normal to a uniform flow are investigated experimentally for thickness-to-chord ratios between 0.05 and 1.92 at Reynolds numbers around 6600. Measurements were conducted using planar, time-resolved stereoscopic particle image velocimetry. A generalized phase average analysis, which invokes elements of mean-field theory to relate the temporal modal coefficients of the fundamental harmonic and slow-varying base-flow drift, provided a statistically significant representation of the coherent cycle-to-cycle variation of the shedding process. It is shown that the characteristics of the wake velocity fluctuations change as a function of the thickness-to-chord ratio and can be related to structural differences in the wake topology. Moreover, the trajectory of shed vortices plays an important role in distinguishing the dynamics observed for different fluctuation-amplitude cycles. Based on differences in amplitude modulation characteristics and the vortex formation region topology, three flow regimes can be defined: a thin-plate regime, for which the feedback between forming vortices and base pressure is important; a cylinder-like thick-plate regime for which the obstacle afterbody suppresses the feedback; and a long-plate regime for which wake periodicity is not associated with the classical Kármán shedding process. The present analysis highlights the importance of the feedback mechanism for the thin-plate regime and helps reconcile differences in the reported critical thickness values between regimes.

Journal

Physical Review FluidsAmerican Physical Society (APS)

Published: Jun 26, 2017

There are no references for this article.

Sorry, we don’t have permission to share this article on DeepDyve,
but here are related articles that you can start reading right now:

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.

See the journals in your area

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

Start Free Trial

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
Start Free Trial

14-day Free Trial