Non-stationary VIM of Two Mono-Column Oil Production Platforms

Besides high stability, FPSO1 platforms present high deck load and storage capacities. They can be converted from existing tankers or built as new structures, specific to oil production and storage, what pushes down the construction costs. Despite those advantages, wave motions response can be a problem, increasing the downtime. SS2 platforms present low response wave motions, though not enough to dry trees application. Low installation costs and high mobility makes a SS also suitable for drilling. However, no storage capacity, besides structural and stability issues still make this well proved concept expensive. Spar platforms combine low wave motions response and stability with high deck load and storage capacities, though at high costs. Spars exhibit VIM (Vortex-Induced Motions) a particular case of VIE (Vortex-Induced Excitation) and are prone to Mathieu like instabilities; [11]. On the other hand, Mono-column platforms (MCP), a relatively new concept, [9], may be designed to combine most of FPSO advantages, as high storage capacity, high stability and simple structures with low response motions and minimum downtime, like the SSs, but at lower costs than Spars.