Objectives  Aiming at the characteristics of semi-submersible vessels with large roll period changes under different working conditions, a passive controllable anti-roll tank with an adjustable harmonic period is designed. The harmonic period is changed by controlling the height of the T-shaped baffle in the tank, generating a better anti-roll effect that matches the ship's roll period.

  Methods  First, the influence of the T-shaped baffle arrangement on the harmonic period of the tank is analyzed though Computational Fluid Dynamics software, and the design of the tank is optimized. Second, in order to adapt to semi-submersible vessels under different working conditions or encountering waves of different frequencies, the auto-regressive (AR) model is used to predict the ship's roll period and adjust the number of raised baffles according to the prediction, on the basis of which the designed water tank is simulated.

  Results  The simulation results show that the designed anti-roll tank can adapt to the different working conditions of semi-submersible vessels with positive effects.

  Conclusions  Changing the number of T-shaped baffles can increase the harmonic period of the tank to a certain extent, and it can be set to match the roll period of the semi-submersible vessel by controlling the baffles, thereby better adapting to ships with large roll period changes and providing strong anti-roll ability.