Viscous damping effect and vortex shedding performance of the novel anti-motion structures on a cylindrical FPSO

Abstract

In order to decrease the dynamic response of cylindrical FPSO, a novel anti-motion structures with taper angle is proposed. According to the computational fluid dynamics approach, the influence of different taper angles and pore diameters are numerically studied in present work. To investigate both viscous damping and vortex shedding performance of heave and pitch motions, dynamic mesh method and user defined functions are adopted. After a series of validation and convergence test works, the numerical models of the cylindrical FPSO with different taper anti-motion structure is established, and the damping coefficients are calculated via these models. Besides, the vortex shedding performance is documented by vorticity graphs. Results show that the heave damping coefficient decreases with the increasing taper angle. On the other hand, less pitch damping coefficients are found when the smaller pore diameter is adopted. An interesting finding is that pores on the anti-motion structure do benefit to increase the damping performance, but the diameter should not exceed a limit.