Numerical and experimental study on motion responses of a dry tree semi-submersible platform with vertically coupled multi-body effects

Abstract This study investigates a new dry tree semi-submersible platform composed of an upper floating body and a lower pontoon. Tendons are used to connect these two parts, which can rotate freely in roll and pitch in order to release the large wave bending moment. To study the motion and tendon performance of the complex multi-body system, this study uses a combination of numerical simulations and experiments to examine the new platform based on 3D multi-body potential theory. The numerical calculation results are in good agreement with the experimental results, and both results prove that the platform has excellent motion and tendon responses. In addition, the tendon lengths and lower pontoon weights are further explored, and their influences on the motion and tendon responses in the coupled multi-body system are obtained. It is helpful to increase the length of the tendon for improving the performance of the motion and tendon, but the effect of which can be ignored when the length is greater than 100 m. The issues concerning the excessive rotation angle and negative load of the tendon can be addressed by changing the weight ratio of the lower pontoon to upper floating body.

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