The three-dimensional green-water event study on a fixed simplified wall-sided ship under freak waves

Abstract

As non-linear extreme waves, freak waves have huge wave crests, large wave heights and concentrated energies. The freak waves usually lead to severe impacts on ships and marine structures in green water events. Nevertheless, the general mechanisms, water motion scenarios and impact loads on bow deck and superstructure in these events remain unclear. In the study, the freak waves based on Peregrine breather solution of NLS equation are generated and the green water events of a fixed ship model are numerically investigated in three-dimensional wave flume by CFD method. First, the accuracy of green water simulation method is validated with experimental data. Then, the propagation and evolution of freak waves in front of ship bow are observed. After that, the water motion scenarios, velocity fields and impact pressures on ship bow in different stages are investigated. The necessity of three-dimensional simulation is verified. The effects of wave heights, wave periods and breaking waves are analyzed. The results indicate the water elevations and largest peak pressures increase nonlinearly with freak wave heights and the short-period freak waves cause more severe impacts than long-period ones.