Wavenumber spectra of short wind waves: laboratory measurements and interpretation

Short wind-generated capillary-gravity waves were measured with a refraction-based optical technique in different wind/wave tanks. Directional wave number spectra were determined from the wave slope images for a wide range of wind speeds and fetches for the different geometries of the laboratory facilities. The shape of the wavenumber spectra and their dependence on die friction velocity and fetch were analyzed. We found that the parasitic capillaries dominate the capillary range of the spectra. The interpretation of the results is given by a physical model of the short wind-wave spectrum that takes the generation of parasitic capillaries under laboratory conditions into account.