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Vortex-induced vibration (VIV) critically accelerates cumulative fatigue failure in marine risers. Traditional helical strakes effectively suppress VIV but induce substantial drag penalties and pose manufacturing challenges due to their complex three-dimensional structure. To address these limitations, a new type of straight-fin helical strake was proposed in this study to balance VIV suppression, drag penalty, and ease of manufacturing. Experimental investigations compared the VIV response of a cylinder with both strake types and without strakes. Hydrodynamic coefficients were calculated using the least squares method based on the energy competition model, and a linear drag prediction model was proposed to quantitatively correlate the drag coefficient with vibration amplitude. The experimental results showed that both strake types provide effective VIV suppression, reducing the excitation coefficient CEY to near-zero under most conditions and narrowing the variation of the added mass coefficient Cmey. Notably, the proposed straight-fin helical strake with a pitch of 17.5D (D is the cylinder diameter) matches the VIV suppression performance of conventional designs. Crucially, it exhibits a better hydrodynamic efficiency, characterized by a lower drag coefficient CD and baseline drag coefficient CD0 within the proposed drag model. The suppression performance of the straight-fin configuration exhibits a sensitivity to the pitch, with the frequency lock-in phenomenon eliminated exclusively at higher pitch. This study validates the 17.5D-pitch straight-fin helical strake as a promising alternative for deep-sea riser applications, offering comparable VIV suppression efficiency alongside a reduced drag penalty.
Shi et al. (Wed,) studied this question.