On the limits of wavy cylinder wavelength and amplitude for effective wake and vortex-shedding control

T. H. New, H. D. Lim, C. H. Chen, Kim Boon Lua*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

An experimental time-resolved particle-image velocimetry study was conducted on wavy cylinders possessing wavelength (λ) and amplitude (a) combinations that are significantly different from earlier studies at ReDm = 2700. Results show that vortex formation length increases as the wavelength decreases from λ/Dm = 2.4 to 1.2, but decreases when the latter decreases to λ/Dm= 0.6. Amplitude increments lead to significant vortex formation length growths and reductions at the saddles/nodes of λ/Dm= 2.4 and 1.2 wavy cylinders, respectively. In contrast, λ/Dm= 0.6 wavy cylinders produce significantly shorter vortex formation lengths like a baseline cylinder, regardless of amplitude. Regular reversed flow “lobes” are observed for λ/Dm= 2.4 and 1.2 wavy cylinders, but not λ/Dm= 0.6 ones, which lead to variations in the spanwise vortex formation lengths. Proper orthogonal decomposition (POD) analysis shows that only a/Dm= 0.4, λ/Dm= 0.6 wavy cylinder has the same vortex-shedding frequency as the baseline cylinder. Other POD results also demonstrate that the vortex-shedding behaviour between λ/Dm= 0.6 wavy and baseline cylinder is very similar. The present study shows that there exists a minimal wavelength below which that coherent streamwise vortices will not be produced and wake control benefits of wavy cylinders will be considerably reduced.

Original languageEnglish
Pages (from-to)597–614
Number of pages8
JournalJournal of Marine Science and Technology
Volume28
Early online date7 Jun 2023
DOIs
Publication statusPublished - 1 Sept 2023

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