TABLE OF CONTENTS Ocean waves may generate significant forces and moments on marine vehicles and fixed structures which must be considered by designers. In the previous chapter, formulas for the wave-induced force on vertical walls and circular cylinders were given. In this chapter we will focus on evaluation of the forces and moments on marine vehicles, and the resulting motions, which are also of considerable interest. We begin by studying the response of a floating body in small-amplitude waves; we will see that the frequency (spectral) analysis introduced in the previous chapter is applicable for determination of the statistics of the wave-induced response. Some important nonlinear effects will be investigated, and the effects of a mooring system will be briefly examined.
We will consider a floating body acted on by waves which can be represented using the linear theory described in the previous Chapter; that is,
in deep water (see Eq. (4.74)) for all components of the incident wave spectrum. This might seem to be overly restrictive, but we will see that the linear theory generally works quite well, even in cases where this assumption is not strictly met. Furthermore, we will assume that the body is stable, so that small disturbances will yield proportionately small responses. In addition, we will for the moment neglect viscosity, which acts to produce some nonlinear effects which we will discuss later. Under these assumptions the body can be represented as a linear system, with the waves as the input,...
