Excitation of capillary waves by longer waves

Abstract
At low wind speeds the shortest capillary waves appear to be generated hydrodynamically and not by the wind. This phenomenon is investigated using a Hamiltonian representation of the surface wave dynamics. A perturbation technique of Kolmogorov is used to transform away non-resonant, nonlinear interactions. Resonant interactions are treated by the Hasselmann transport equation, applied to the transformed variables. Calculated spectra show reasonable agreement with the observations of Jähne & Riemer (1990).