Numerical investigation on the water entry of bow-flare section with different bulbous bow shapes

Water entry is one of the important topics in ship and offshore structures. Among the structures, water entry of bow-flare section with bulbous bow could be one of the most difficult problems due to its complex geometry. To investigate the problem, a numerical model which can simulate water entry of complex objects is developed in this paper. In the framework of Cartesian grid, Volume of Fluid method combined with Piecewise Linear Interface Construction (VOF-PLIC) are used to capture free interface. Besides, Volume of Solid based Immersed Boundary (VOS-IB) method are adopted to enforce the body boundary condition. To validate the model, water entry of a wedge and a ship hull section with bulbous bow in calm water are simulated. Time histories of pressure and local force are compared with previous experimental results. Then, a series of simulations are conducted for the water entry of bow-flare sections with different bulbous bows. Three bulbous bow shapes namely 'Delta', 'Oval' and 'Nabla' are considered. The influence of bulbous bow shape on the hydrodynamic forces are analyzed and three peaks are observed. A detailed discussion on the three peaks is performed with special attention paid to the second peak. It is observed that the shape of bulbous bow shape has non-negligible influence on the pressure distribution during the secondary flare impact. Based on the impact characteristics, recommendations for which shape of bulbous bow to use are given.