ON THE TURBULENCE INDUCED BY NON-BREAKING SURFACE WAVES

etc15 Tracking Number 449

Upper ocean turbulence is a very relevant process within the context of quantifying the exchange between the atmosphere and the ocean. We present results of a study of turbulence induced by non-breaking waves from detailed observation in a small wave tank facility in the Faculty of Marine Science of the University of Baja California. The experiments were carried out with mechanically generated monochromatic waves in a tank of approximately 12m x 0.5m x 0.3m with a varying steepness (ak) from about 0.02 to 0.18, and detailed measurements of the vertical profile of the 3d velocity field within a water column of about 0.035 m in length. Routine data quality control includes the use of only high beam correlation signal within each of the acoustic beams used by the profiler. A rotation matrix was applied to the velocity data matrix in order to secure that the x, y, and z axes were properly aligned with the wave tank. Rather low wave reflection was obtained through the implementation of a beach at the end of the wave tank. The intermittent character of the turbulence present is shown as a region following the -5/3 power law in the spectrum. Nevertheless, this spectral shape is being observed in most of our experimental results, particularly in those where the wave steepness was not too small. Root mean square values are obtained from the turbulent fluctuations time series to evaluate an integral quantity to characterize the turbulence intensity. This intensity is analyzed in terms of the wave steepness showing a linear relationship. The turbulent kinetic energy dissipation rate is also estimated and the relevance of the velocity spectra directly estimated over a limited number of wavenumber bands is addressed. This work represents a RugDiSMar Project (CONACYT 155793) contribution and support from CONACYT project CB-2011-01- 168173 is greatly appreciated.