This paper reports the main results of an investigation on the effects of hydrodynamic interactions on current forces on a typical shuttle tanker, when offloading a FPSO moored in SMS configuration. In this situation, large angles between the direction of environmental agents and the platform centerline may exist and cause intense disturbance on the wind, waves and current fields that reach the shuttle tanker. A procedure for incorporating the FPSO wake on the current forces was proposed and validated by means of a series of towing-tank tests. In this article, the methodology is applied to evaluate how the disturbances in the incoming flow may affect the DP thrust allocation and power consumption during typical offloading operations. Wake effects on the tanker behavior after DP failures are also investigated. It is shown that current wake effects may contribute to an increase in power demand even for typical distances between ships, usually adopted for the safety reasons. They might also influence the ship course after a drive-off failure, with consequences on maneuvering decisions.

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