Kinetics of large scale vertical flow generation by weakly noncollinear nonlinear gravitational waves

The generation of a large-scale vortex flow by gravity waves on the water surface has been experimentally studied. It is shown that large-scale flows are formed as a result of the interaction between nonlinear low-frequency modes which intersect at small angles. The amplitude of vorticity at large scales increases with increasing angle between pump waves. The experimental data agree well with the developed theoretical model. (paper)