Numerical investigation into combined global and local hydroelastic response in a large container ship based on two-way coupled CFD and FEA

In this study, for efficient safety assessment of a ship's hull girder subjected to a combination of the global vertical bending moment (VBM) and the local double-bottom bending moment (DBM), a numerical method based on a coupled computational fluid dynamics (CFD) and finite-element analysis (FEA) is first developed. The mutual two-way coupled CFD and FEA in which the elastic deformation of the ship is taken over to the CFD solutions is employed. The present two-way coupled method is developed in two steps, in a weakly coupled manner and a strongly coupled manner. The developed two-way coupled methods are validated via a comparative study against the available experimental results and the straightforward one-way coupled CFD and FEA in terms of the rigid body motion, VBM, and local water pressure. Using the present strongly coupled method, the added mass with regards to the elastic deformation of the ship is reflected in the results of a decrease in the frequency of 2-node vibration mode of the ship or the vibratory (hydroelastic) component in the water pressure. Then, the DBM is evaluated using the estimated water pressure on the ship bottom. An investigation is finally made into the effect of the hydroelastic component in the DBM on the total DBM and the hull girder ultimate strength.