In recent years, because of enforcement of Energy Efficient Design Index (EEDI), ship hulls with high propulsion efficiency must be developed, which necessitates to investigate the distribution of local pressure induced by a fluid on the hull surface. Global physical quantities such as ship motions estimated with Enhanced Unified Theory (EUT) proposed by Kashiwagi (1995) show good agreement with experimental results, whereas local physical quantities such as unsteady pressures are not in good agreement around the bulbous bow. The solution of the velocity potential by EUT includes a homogeneous component which represents 3D and forward-speed effects, and its coefficient can be determined from matching with an outer solution. We found that the predicted pressure sharply changes at a transverse section around the bulbous bow, and that the cause in sharp change exists in the calculation of the homogeneous component of the velocity potential around the bulbous bow. It is identified that the numerical computation becomes inaccurate when the imaginary part of 2D Kochin function in heave is very small. In this case, some improvements in the calculation method are required. To obtain a reasonable value of the homogeneous-solution coefficient, this article proposes a practical estimation method using interpolation in terms of corresponding values at some transverse sections outside the bow area. To confirm the validity of this method, wave-induced unsteady pressures predicted by this method are compared with experimental data, measured by the authors using the ship model of bulk carrier.
In recent years, Energy Efficiency Design Index (EEDI) came into effect, and the level of its regulation will be strengthened gradually. Therefore, ship designs in propulsion efficiency are required to be more eco-friendly than before. In the field of seakeeping, studies have been conducted on accurate estimation of global physical quantities such as ship motions, hydrodynamic forces, and added resistance, which have contributed so far to the design of eco-friendly ships. However, in order to adapt the restriction of EEDI, from the viewpoint of seakeeping, we need to pay attention to not only global physical quantities but also local ones such as unsteady pressure on the ship hull.
