Energy input amplifies nonlinear dynamics of deep water wave groups

A possible physical mechanism for the formation of freak waves on the open ocean is the localized interactions between wind and waves.Such interactions are highly complex and are currently poorly understood at the scale of an individual wave.Rather than attempt to model the detailed transfer of energy from wind to waves, we simply consider the modifications to wave group dynamics of adding energy to the system. We carried out numerical experiments on isolated wave groups using an excited version of the nonlinear Schrödinger equation. Energy input enhances any soliton-like structures relative to regular waves for unidirectional propagation. For directionally spread wave groups, energy input enhances the nonlinear changes to the shapes of focused wave groups: Groups contract in the mean wave direction and expand in the lateral direction to a significantly greater degree than observed for nonexcited wave groups.