Experimental investigation on the hydrodynamic characteristics of extreme wave groups over unidirectional sloping bathymetry

A series of physical experiments were conducted to investigate the characteristics of extreme wave groups over a shoal. An improved method for detecting wave groups based on instantaneous energy was verified, which can identify wave groups reasonably and effectively. As a result, it was found that a linear relationship exists between the wave group energy and group time length on the logarithmic coordinate diagram, and the same tendency holds for extreme wave groups. Moreover, a steeper slope of the linear curve was observed for larger significant wave heights, indicating that the significant wave height significantly affects the wave heights and energy levels of extreme wave groups. The research also found that the average energy of the identified extreme wave group is approximately twice the average energy of the recorded data, thereby supporting the hypothesis that the wave group plays an important role in the generation of extreme waves.