Mitigation of Vortex-Induced Vibration of Cylinders Using Cactus-Shaped Cross Sections in Subcritical Flow

Flexible cylinders, such as marine risers, often experience sustained vortex-induced vibrations (VIVs). Installing helical strakes on a riser is the most widely used technique to mitigate VIVs. This study was inspired by giant Saguaro Cacti which can withstand strong wind with shallow root system. In this study, numerical simulations of flow past stationary cylinder cactus-shaped cross-section in two-dimensional field at subcritical Reynolds number 3900 were performed. Results show that cylinders have lower lift coefficient without increasing drag compared those circular cylinder. VIV experiments single flexible pipe well set two tandem-arranged pipes conducted different reduced velocities investigate effects streamwise spacing and wake cactus-like body shape mitigation. Experimental results responses upstream position no cost increased drag; however, similar strakes, efficiency mitigation for downstream reduced. Although shapes tested not optimized oscillation suppression, still suggests modification cross-sectional well-designed has potentials be an alternative technology risers.