Turret mooring systems are extensively used as the primary station keeping component for ship-shaped offshore floating production and storage vessels. The location of the turret is one of the most important design parameters affecting the dynamic behaviour of the vessel in terms of motion stability and mooring line loading. The present paper describes physical model testing of a moored monohull with varying turret location conducted in the Ocean Wave Basin at HR Wallingford. The vessel and moorings are examined in weather conditions such that wind induced loading causes the vessel to take up a non-zero mean yaw offset to the waves. Six degree of freedom motions were measured in the tests together with mooring line tensions. The experimental results are compared with time domain simulation of non-linear drift motions. Conclusions are drawn upon the influence of turret position on the motions of the moored vessel in non-head-sea situations. The yawing motion of the vessel is specifically highlighted as this can cause large increases in horizontal drift loading and has implications for green water on deck, off-loading and production downtime. Results for varying wind direction relative to waves are also presented. There is generally good correlation between the experimental measurements and time domain motion predictions.
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