Shows how wave loads on fixed bodies can be computed, within a linear framework as well as including viscous effects. The validity of the slender body assumption is addressed and MacCamy and Fuchs’ theory is introduced to account for diameter-to-wavelength ratios which are not very small. The concepts of modal mass and loads are introduced. Nonlinear wave loads such as ringing and slamming are discussed.

This chapter tackles a few nonlinear effects that cannot be rendered by linear or second-order potential flow theory. Higher than second-order wave loads, usually denoted as ringing loads (at variance with springing which is second-order), are first considered and third-order diffraction theory is outlined and applied to a vertical cylinder. Important and ill-known phenomena that are also due to third-order nonlinearities are the wave runups often seen at sea-walls or ship hulls in beam seas. These are due to third-order interactions between the incoming waves and the radiated and diffracted waves by the structure. Example is given in the academic case of a vertical plate of finite length, where experimental results are compared with a simple parabolic model. Parametric instabilities are considered next. A long section is devoted to impact and slamming loads, where the so-called von Karman and Wagner approximations are presented along with more elaborate theoretical models. Finally the hydrodynamics of porous (or perforated) bodies is considered.