However, the values of both L /l = 0.9 and udsp = 0.017 m s− 1 are typical of calm conditions. Moreover, in this case udsp is close to the model value of usp0¯=0.025ms−1, when the spreading rate is defined only by the spreading coefficients. The fact that the slick shape is nearly circular during the above measurement is confirmed by Figure 9. This shows a photograph of the sea surface, converted into the horizontal Cartesian coordinate system, obtained
2100 sec after the spill. The location of the slick in Figure 9 is indicated by R428 the arrow. We estimated the wind wave action on SF spreading using frequency spectra at f ≤ 1 Hz. The calculation of S(f) at f > 1 Hz is not correct owing to the distortion associated with short-wave advection in the field of long-wave orbital velocities. The influence of the high-frequency part of S(f) on SF spreading will require further study. The investigations of the dynamics of a vegetable oil film on the sea surface were carried out in the vicinity of the Marine Hydrophysical Institute’s research platform (off the southern coast of Crimea, 44°23′35″N, 33°59′4″E) under a wide range of wind speeds and wave conditions. Slick sizes were estimated from PD98059 photographic images of the sea
surface covered by the surface film. Analysis of the experimental results showed that the behaviour of the surface film varies, depending on the wind conditions. Film spots tended to become elongate in the direction of the wind flow, taking the form of an ellipse. The rate of semi-major axis growth increases from 0.039 to 0.145 m s− 1 when U increases from 6.3 to 11.7 m s− 1. In the experiments carried out at wind speeds less than 4 m s− 1 and a significant time interval, the law L ∼ t3/4 was obeyed. According to Fay’s classification this corresponds to the spreading mode of the dominant forces of surface tension. The experimental results show the absence of an explicit dependence of significant wave height from 0.15 to 1.03 m on film spreading rate. The values of the
spreading rates obtained at a weak wind of 1.6 m s− 1 but different values of the significant wave heights BCKDHB (Hs = 0.62 and Hs = 0.15 m) are practically the same. The research leading to these results received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 287844 for the project ‘Towards Coast to Coast NETworks of marine protected areas (from the shore to the high and deep sea), coupled with sea-based wind energy potential (CoCoNET)’. Financial support was also re-ceived from IFREMER (Contracts Nos. 2011 2 20712376 and 2012 2 20712805 between IFREMER and Small enterprise DVS LTD). “
“Water dynamics in the coastal zone of tideless seas is determined by the energy transmitted in waves and currents, the decisive part being by surface waves impacting on the beach.