Modelling of Ship Waves from High-speed Vessels

Waves generated by high-speed vessels may differ considerably from the ship wakes generated by conventional ships. Wakes from high-speed vessels typically have long wave periods, and occasionally very large amplitudes. The wave fan is often much wider than for conventional ships, and the leading waves can be highly nonlinear. This is particularly an issue in shallow coastal waters, and for coastal regions not exposed to large sea swell or impact from large wind generated waves. As a steadily increasing number of high-speed crafts are put into service, particularly in passenger ferry traffic, more coastal regions are exposed to wash from high-speed vessel wakes, causing concern with respect to public safety, potential damage of coastal structures, and potential environmental impact. Speed reduction will often, but not always, mitigate the problem. Furthermore, such measures are in conflict with the interests of ferry operators and the general public concerning fast transportation at sea. A careful planning of ship routes and speed regimes is needed to optimize the ship operation, while maintaining acceptable wash levels at the shore. This review presents some of the basic properties of ship wakes, and show how numerical models can be used to model waves generated by high-speed vessels. The presentation starts with a discussion of basic properties of ship wakes, and a demonstration of why high-speed vessel wakes are different from the wakes generated by conventional ships. Thereafter we discuss the mathematical equations that can be used to model such waves, and some basic properties of these equations. Finally we discuss numerical models based on these equations, and how these models can be used to simulate ship wakes.