Un Procedimiento Numérico Expedito para Representaςão de Turrets na Análise Acoplada de Movimientos de Sistemas Flutuantes Offshore

Abstract

This work presents an expedite and efficient numerical tool to model turret-based mooring systems. Such systems are employed in oil production offshore platforms, known as FPSO (Floating Production, Storage and Offloading units). The turret allows aligning the ship with the wind, wave and current resultant force components, decreasing the horizontal displacement of the hull and consequently the tensions of the mooring systems. Nowadays, traditional simulation programs for offshore systems are not prepared to consider appropriately the purpose of the turrets; the numerical models are usually built to consider the center of the turret as a unique connection to the ship, in which all the anchor lines and risers are connected . This allow the yaw motion to not twist the lines, keeping the turret function, but on the other hand does not consider strictly the actual position of the top connection (disposed in a polar way, with radii that can exceed 5m). That means that the moments evaluated by the top tension of the lines with the longitudinal and transversal axes of the ship cannot be correct. Besides, with the top connections in a single point the numerical coupled model does not ensure that the configuration of the lines represents accurately that ones installed in the oil production field, decreasing the quality of the mooring design. The coupled numerical tool presented in this work is prepared to deal adequately with the turret system, allowing considering the real coordinates of the top line connections, helping to improve the quality of the mooring designs. This work shows the numerical formulation implemented, and compares these two modeling procedures in a case study of FPSO turret system submitted to environmental conditions.