Objective  The moonpool of drillship in waves will have an adverse impact on the motion of hull itself, leading to a large amplitude of motions, especially in terms of heave motion, which can cause damages to the relevant functional equipments onboard. This paper attempts to address the issue by arranging symmetrical thick plates in the moonpool.

  Methods  On the basis of the potential flow theory and the constructed frequency-domain mathematical model, the impacts of length-width ratio and draft of moonpool and layout height of thick plate on the heave motion of hull were numerically calculated and analyzed. A floating production storage and offloading (FPSO) ship with moonpool was then selected to carry out frequency-domain numerical calculation of heave motion of hull in waves by the use of AQWA software. Comparison of the calculated results with the published experimental results in the open literature was done to verify the feasibility and reliability of the proposed method in this paper.

  Results  The results show that, if the upper surface of the thick plates is actually at the level of the still water surface, the heave motion of ship hull excited by flow resonance in the moonpool will effectively suppressed.

  Conclusion  The results of this research can provide valuable references for suppressing the heave motion of ships with moonpools.