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

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 Re Dm  = 2700. Results show that vortex formation length increases as the wavelength decrea...

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Bibliographic Details
Published in:Journal of marine science and technology 2023-09, Vol.28 (3), p.597-614
Main Authors: New, T. H., Lim, H. D., Chen, C. H., Lua, K. B.
Format: Article
Language:English
Subjects:
Amplitude
Amplitudes
Automotive Engineering
Cylinders
Engineering
Engineering Design
Engineering Fluid Dynamics
Fluid flow
Mechanical Engineering
Offshore Engineering
Original Article
Particle image velocimetry
Proper Orthogonal Decomposition
Reversed flow
Saddles
Vortex shedding
Vortices
Wavelength
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Summary: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 Re Dm  = 2700. Results show that vortex formation length increases as the wavelength decreases from λ/D m  = 2.4 to 1.2, but decreases when the latter decreases to λ/D m  = 0.6. Amplitude increments lead to significant vortex formation length growths and reductions at the saddles/nodes of λ/D m  = 2.4 and 1.2 wavy cylinders, respectively. In contrast, λ/D m  = 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/D m  = 2.4 and 1.2 wavy cylinders, but not λ/D m  = 0.6 ones, which lead to variations in the spanwise vortex formation lengths. Proper orthogonal decomposition (POD) analysis shows that only a/D m  = 0.4, λ/D m  = 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/D m  = 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.
ISSN:0948-4280
1437-8213
DOI:10.1007/s00773-023-00943-8