Particle transport by internal breathers

The processes of particle transport induced by internal breathers in quasi three-layer fluid are investigated in the framework of weakly nonlinear theory. We use the Gardner equation to describe the displacement at the maximum of vertical baroclinic mode. To determine the fields of vertical and horizontal velocities, which are used for calculating of Lagrangian particle trajectories, we apply three versions of the wave fields' vertical structure: linear mode, weakly nonlinear approximation (with taking into account the first nonlinear correction to linear mode) and weakly nonlinear-weakly dispersive approximation (with taking into account both the first nonlinear correction and the first dispersive correction to linear mode). The processes of particle transport are investigated for different initial configurations of breathers, as the velocity fields induced by nonlinear wave packets are substantially different for breathers with different phases. The comparison of the form of particle trajectories for different horizons and different breathers' configurations is made. It is shown that the use of the weakly nonlinear model is sufficient to determine the trajectories of fluid particles. Taking into account the first dispersive correction to the modal function almost does not affect particles' displacements, neither qualitatively, nor quantitatively. A significant difference between solutions of the problem of fluid particles' trajectories for two types of nonlinear wave motions in a stratified fluid-solitons and breathers-is revealed.