Study of the wet-towing transportation of an FPSO with elastomeric-supporting topside modules

Abstract

This study focuses on the wet-towing transportation of an FPSO with elastomeric-supporting topside modules. In the study, an approximation method is utilized to calculate the wet-towing resistance in the design sea state for determining the wet-towing configuration. Meanwhile, the study successfully achieves to simulate the hydrodynamic responses and structural interactions synchronously for the complex wet-towing system. This numerical method is applied to the feasibility analysis of the wet-towing configuration in the design sea state, which indicates that the mean wet-towing resistance, peak towline tension, and dynamic responses of the FPSO are all within the design scope, proving that the wet-towing configuration is feasible. A parameter sensitivity analysis is performed for the wet-towing transportation, which reveals that the increase in towing speed and severity of sea state results in larger towing resistance. Extending the towline length has a significant dampening effect on both peak towline tension and its fluctuation during extreme sea state. The excursions of wind, wave, and current incident directions from the towing route can lead to the offsets of the FPSO, so an auxiliary tug is necessary to keep the FPSO in the planned route, and the wet tow in head sea is recommended.