Waves: Nonlinear wave theories

OrcaFlex models two types of waves, periodic regular waves and random waves. A regular wave is a periodic wave with a single period. A random wave in OrcaFlex is a superposition of a number of regular linear waves of differing heights and periods. We shall not discuss random waves here.

For very small waves in deep water, Airy wave theory (also known as linear wave theory) is valid. Many waves in practical engineering use do not, however, fall into this category, hence the need for nonlinear wave theories. These include Stokes' 5th order theory, Dean's stream function theory and Fenton's cnoidal theory, which are all available in OrcaFlex. We give an outline of these theories here in the form of concise abbreviations of the relevant papers. See Stokes' 5th, Dean's stream function theory and Fenton's cnoidal theory for a brief overview of each of the nonlinear wave theories, and ranges of applicability for guidance on how to decide on which wave theory to use in practice.

For an overview of all the theories considered here see Sobey R J, Goodwin P, Thieke R J and Westberg R J, 1987.