Linear and nonlinear based ship motion of a naval combatant model

Seakeeping is a very complex problem in Maritime problems involving at least 3 degree-of-freedom (3-DOF) motion of the hull and until commercialized CFD softwares became widely used, the problem was approached by linear approaching applying potential theory. With this motivation, two kinds of numerical methods are employed to study the vertical motions for one encounter frequency where experimental results are available in the literature. While the first method is widely known linear “strip theory”, the other one is the fully non-linear U-RANS solver. DTMB 5415 ship form is selected for the computational work. In the first method, the hydrodynamic coefficients in the motion equations are determined and ship responses are found. In the second method, ship responses are found by solving Newton’s Motion Law after calculating forces/moments acting on the ship hull via the FVM (Finite Volume Method). Computational study is carried out for Fn=0.41 only. Results are validated with experiments and comparisons are made between the two numerical approaches.