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, K. B. Lua*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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
JournalJournal of Marine Science and Technology
StateAccepted/In press - 2023


  • Flow separation
  • Particle-image velocimetry
  • Wake control
  • Wavy cylinder


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