NONLINEAR TRANSFORMATION OF IRREGULAR WAVES IN SHALLOW WATER

Abstract

Propagation and shoaling of irregular wave trains in shallow water is a nonlinear process, where substantial cross spectral energy transfer can take place in relatively short distances. This process involves the generation of bound sub- and super-harmonics and near-resonant triad interactions, which are defined as the energy exchange between three interacting wave modes. In the literature it is common practice to distinguish between bound waves and resonant free triads. The theory for bound waves is based on the assumption of a one way transfer of energy to generate higher and lower harmonics which are phase locked to the primary wave train. In reality, however, a feed back of energy to the primary frequencies will occur leading to nearresonant interactions.