Experimental investigation on straight-fin helical strakes with varying geometric parameters for vortex-induced vibration suppression

Abstract

This paper experimentally investigates a simplified straight-fin helical strake for vortex-induced vibration (VIV) suppression of cylindrical structures, aiming to mitigate manufacturing difficulties and drag penalties of conventional strakes. Tests cover Re = 2×10 4 –1×10 5 and Ur = 2–15, evaluating bare cylinders and 11 straked configurations with varying fin length ( l / D ), height ( h / D ), and pitch ( p / D ). Results show that most configurations reduce vibration amplitudes and narrow lock-in, but performance varies nonlinearly with geometry. The optimal case ( l / D = 1.0, h / D = 0.2, p / D = 17.5) within the tested configurations achieves over 98% maximum amplitude reduction and nearly eliminates lock-in. Hydrodynamic analysis reveals lower excitation force coefficients C Ey for straked cylinders, positively correlated with amplitude. The drag coefficient C D generally increased after the installation of strakes, the pronounced C D peak during the lock-in is suppressed despite intrinsically increased mean drag. Several configurations maintain mean C D between 1.4 and 1.6 while achieving substantial suppression, balancing suppression effectiveness and drag penalty. Added mass coefficients C mey show scattered trends without obvious parameter-dependent trends. Overall, straight-fin helical strakes offer a promising passive VIV suppression device with balanced effectiveness and drag penalty.