Investigation on suppression of Vortex-Induced vibration using helical strakes

Tongming Zhou, Siti Fatin Mohd Razali, Liang Cheng

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

While the effect of helical strakes on suppression of Vortex-Induced Vibrations (VIV) has been studied extensively, the mechanism of VIV mitigation using helical strakes is less well documented in the literature. In the present study, experiments were conducted in a wind tunnel at four velocities, i.e. 1.92, 3.83, 5.74 and 7.65 m/s. Strakes with a dimension of 10d in pitch and 0.12d in height were fitted onto a rigid cylinder of diameter d = 80mm, and subjected to a transverse air flow. Hotwire techniques were used to measure the instantaneous velocity fluctuations at various locations to explore the mechanism for VIV mitigation by using helical strakes. It was found that the helical strakes reduce VIV by about 98%. Unlike the bare cylinder which experiences lock-in over the reduced velocity of 5 ∼ 9, the straked cylinder does not show any lock-in region. In exploring the mechanism of VIV reduction by helical strakes, it was found that vortices shed from the straked cylinder are weakened significantly. The dominant frequency of the vortex structures along the spanwise direction of the bare cylinder was very stable. This is not the case for the straked cylinder wake, which differs by about 36% of the averaged peak frequency over the length of 3.125d along the cylinder axial direction, indicating that the vortex shed from the latter is outof-phase and mismatching. This is supported by the phase shift between the velocity signals measured at two locations separated in the spanwise direction. The cross-correlation coefficients in the bare cylinder wake were much larger than that obtained in the straked cylinder wake, indicating that the correlation length of the former is much larger than that of the latter.

Original languageEnglish
Title of host publicationProceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE
Pages891-900
Number of pages10
Volume6
DOIs
Publication statusPublished - 2010
Externally publishedYes
EventASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2010 - Shanghai
Duration: 6 Jun 201011 Jun 2010

Other

OtherASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2010
CityShanghai
Period6/6/1011/6/10

Fingerprint

Vortex flow
Phase shift
Wind tunnels
Air
Experiments

ASJC Scopus subject areas

  • Ocean Engineering
  • Mechanical Engineering
  • Energy Engineering and Power Technology

Cite this

Zhou, T., Mohd Razali, S. F., & Cheng, L. (2010). Investigation on suppression of Vortex-Induced vibration using helical strakes. In Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE (Vol. 6, pp. 891-900) https://doi.org/10.1115/OMAE2010-20984

Investigation on suppression of Vortex-Induced vibration using helical strakes. / Zhou, Tongming; Mohd Razali, Siti Fatin; Cheng, Liang.

Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. Vol. 6 2010. p. 891-900.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Zhou, T, Mohd Razali, SF & Cheng, L 2010, Investigation on suppression of Vortex-Induced vibration using helical strakes. in Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. vol. 6, pp. 891-900, ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2010, Shanghai, 6/6/10. https://doi.org/10.1115/OMAE2010-20984
Zhou T, Mohd Razali SF, Cheng L. Investigation on suppression of Vortex-Induced vibration using helical strakes. In Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. Vol. 6. 2010. p. 891-900 https://doi.org/10.1115/OMAE2010-20984
Zhou, Tongming ; Mohd Razali, Siti Fatin ; Cheng, Liang. / Investigation on suppression of Vortex-Induced vibration using helical strakes. Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. Vol. 6 2010. pp. 891-900
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