Comparison of Serrated Helical Strakes in Suppressing the Vortex-Induced Vibrations of a Circular Cylinder
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The present work presents an experimental investigation of the suppression of vortex-induced vibrations of a circular cylinder by means of helical strakes. Experiments have been per- formed in a water channel at moderate Reynolds numbers. Three different types of helical strakes are compared: (i) a continuous helical strake, (ii) a helical strake with serrated blades and (iii) a helical strake with serrated blades but inverted (negative) in relation to the helical pitch of the strake. While the serrated- blade strake appeared as an improvement over the conventional model, the novel negative-bladed strake produced worse results, allowing for the return of resonant VIV. The most effective VIV suppressor was the bladed strake, achieving a reduction of 88% in the peak amplitude of vibration when compared to that of a bare cylinder during resonance. We conclude that simply inverting the local angle of attack of the individual blades (or fins) in relation to the helical pitch of the strake does not improve the performance of the strake in terms of VIV suppression.
KeywordsVortex-induced vibration Suppression Circular cylinders Helical strakes
We gratefully acknowledge support of the RCGI Research Centre for Gas Innovation, hosted by the University of São Paulo (USP) and sponsored by FAPESP São Paulo Research Foundation (2014/50279-4) and Shell Brasil. GRSA acknowledges the support of FAPESP (2011/00205-6) and CNPq (306917/2015-7).
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