This paper presents a method of assessing fatigue life due to slamming on the structural components inside drillship moonpools with a recess. The effect of free surface deformation in the moonpool, the resulting slamming pressure on the moonpool’s bulkheads, and the resulting stresses and fatigue life are studied for two typical drillship moonpools with a recess.
The fatigue life is predicted using a practical engineering approach. The natural period of the moonpool is determined by using a potential flow radiation/diffraction solver. The flow characteristics and slamming pressure in the moonpool are calculated using CFD. Subsequently, the slamming pressure results are used in a structural FEM model to calculate the stress on the structural elements. The fatigue life of the structure inside the moonpool is predicted using suitable S-N curves from classification society rules.
In this paper, a high-level description of the problem is made, the methodology for the prediction of fatigue life of the critical structural elements in the moonpool is described, and mitigation solutions are proposed to increase the fatigue life of the structural components.