Spectra of turbulent fluctuations over ocean waves

Abstract

Spectral analyses are performed on turbulence data obtained over natural ocean waves during BOMEX. Results are obtained for variance and co-variance spectra, phase and coherence relationships, and amplitude ratios. Peaks in the horizontal and vertical velocity spectra are observed to correspond to the frequency of the wave spectra peaks. Phase relationships tend to obey predictions of potential flow theory in regions of the wave spectra peaks. However, the wave related motion contributes to the momentum transfer which is not predicted by potential flow theory. The ratio of the wave induced disturbance to the sea surface displacement is used to locate the wave spectra frequency for which the level of measurement is a critical level. Results of the study are readily compared to existing wind-wave coupling theories, both linear and non-linear.