Two identical tandem square prisms with rounded edges and hard marine fouling at incidence in cross-flow: Effect of spacing and Reynolds number on unsteady fluid dynamics

Because of their long submerged columns, deep-draft semi-submersible floating structures are particularly susceptible to vortex-induced motions. This paper focuses on the steady and unsteady forces that act such a column pair, as well frequency strength shed vortices behind downstream column. Wind tunnel experiments were performed two rounded lightly rough square-section prisms in cross-flow for Reynolds numbers from 100,000 up 7 million. They arranged inline at centre-to-centre distances S/D = 2.8, 4, 5.6 0° or 45° incidence angle. The trend drag curve upstream prism deviates 2.8 4 sharply single prism. force strongly depends both α. At thrust occurs either certain (α 0°) all 45°) flow states. Larger spacing values lead an overall higher flattening Cd2 (ReD) curve. highest fluctuating lift obtained α 45°. Regarding vortex shedding frequency, differences between angles occur only.