Formation and decay of vortex motion on a liquid surface (scientific summary)

The experimental studies supported by the Russian Science Foundation, project no. 17-01525, have been briefly reviewed. Processes of formation and decay of vortex structures on a water surface have been studied. Vortex motions in the liquid have been excited by gravity waves propagating on the surface in different directions. It has been shown that the process of formation and decay of the vorticity on the surface can be described by the sum of two mechanisms-Stokes' drag and generation of a solenoidal flow by interacting nonlinear surface waves. It has been shown that the processes of formation and decay of vortex structures after the beginning (or end) of the wave excitation at times smaller than the time of viscous damping of the wave are due to changes in the wave system. The process of formation at times much larger than the time of viscous damping is due only to the nonlinear mechanism of generation of the vorticity, whereas the process of decay is due to viscous losses. In the intermediate time interval, the intense interaction of vortices leads to the redistribution of energy between different scales.