Field study of film spreading on a sea surface

The results of a field study of surface film spreading on the sea surface are presented. The experiments were carried out in the coastal zone of the Black Sea in a wide range of wind speeds and wave conditions. Vegetable oil was used for preparing the surfactants. It was found that at moderate and strong wind speeds the slicks take on a shape similar to an ellipse and are orientated in the direction of the air flow. An increase in the speed of the spreading slick along its major axis with strong wind was discovered

Modulation of Wind-Wave Breaking by Long Surface Waves

This paper reports the results of field measurements of wave breaking modulations by dominant surface waves, taken from the Black Sea research platform at wind speeds ranging from 10 to 20 m/s. Wave breaking events were detected by video recordings of the sea surface synchronized and collocated with the wave gauge measurements. As observed, the main contribution to the fraction of the sea surface covered by whitecaps comes from the breaking of short gravity waves, with phase velocities exceeding 1.25 m/s. Averaging of the wave breaking over the same phases of the dominant long surface waves (LWs, with wavelengths in the range from 32 to 69 m) revealed strong modulation of whitecaps. Wave breaking occurs mainly on the crests of LWs and disappears in their troughs. Data analysis in terms of the modulation transfer function (MTF) shows that the magnitude of the MTF is about 20, it is weakly wind-dependent, and the maximum of whitecapping is windward-shifted from the LW-crest by 15 deg. A simple model of whitecaps modulations by the long waves is suggested. This model is in quantitative agreement with the measurements and correctly reproduces the modulations’ magnitude, phase, and non-sinusoidal shape