Spoiler plate effects on the suppression of vortex-induced motions of a single circular cylinder

Abstract

Several methodologies have been proposed to mitigate vortex-induced motions (VIM) on offshore structures, such as the use of strakes, splitter plates, and spoiler plates. Among the mitigation devices, spoiler plates remain insufficiently explored. Given the situation, a parametric experimental investigation was undertaken to investigate the suppression of vortex-induced motions of a circular cylinder with a low aspect ratio using spoiler plates. The experiments were carried out in a towing tank. The circular cylinder tested had an aspect ratio (L/D) of 1.5, which is typically employed in monocolumns and columns of semi-submersible (SS) platforms. Several configurations were investigated by changing the spoiler plate aspect ratio (AR,S), the number of rings with spoiler plates along the vertical axis of the cylinder (nL), and the number of spoiler plates per ring (nD). The reduced velocities investigated varied from 1 to 12, and the Reynolds number from 12,500 to 95,000. The results demonstrated the occurrence of a desynchronization of the vortex shedding, which led to a significant reduction of the in-line and transverse amplitudes. Moreover, a decrease in drag forces of approximately 50% occurred for the most improved case, compared with a bare cylinder, demonstrating a potential solution for this mitigation device.