Experimental and numerical investigation on anti-rolling performance of a DP semi-submersible platform based on thruster group biasing

For semi-submersible platforms equipped with dynamic positioning (DP) system, which has a small water-plane area and low metacentric height, roll motion will be affected by the lateral control force of the thrusters, causing a larger roll amplitude. In view of this problem, present paper proposes a thrust allocation method based on thruster group biasing. The thruster axial forces in group counteract each other while the normal force directions are opposite to form an anti-rolling moment, so that the roll damping can be enhanced without affecting the positioning performance in the horizontal plane. The roll stabilization mechanism is studied experimentally and numerically. A numerical wave tank based on computational fluid dynamics (CFD) method is established, verified and validated against the experiments. Both experimental and numerical results show that the thruster group biasing strategy can increase roll damping and reduce the roll motion of the platform by approximately 16% under the given sea condition.