E. A. Ruvinskaya, O. E. Kurkina, A. A. Kurkin, A. A. Naumov
The distinctive features of particle transport during the propagation of long nonlinear localized wave packets (breathers) in quasi three-layer fluid are investigated in the framework of weakly nonlinear theory. To describe the displacement at the maximum of vertical baroclinic mode the Gardner equation is used. To determine the fields of displacements, vertical and horizontal velocities, which are used for finding of Lagrangian particle trajectories, three variants of the wave fields’ vertical structure are used: linear mode, weakly nonlinear approximation (with taking into account the first nonlinear amendment to linear mode) and weakly nonlinear weakly dispersive approximation (with taking into account both the first nonlinear amendment and the first dispersive amendment to linear mode). Since the velocity fields induced by nonlinear wave packets change immediately, the processes of particle transport are investigated for different initial configurations of breathers. 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 amendment to the modal function almost does not affect the quality and quantity of particles’ displacements. 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.