Chaotic advection in two layers flow above the isolated bottom obstacle: the role of unsteady-perturbation frequency

We consider a model of a point vortex in a two-layer quasi-geostrophic flow. In this model, the chaotization of the phase space strongly depends on the frequency of the external excitation. Numerical experiments show that the degree of chaotization as a function of the excitation frequency has a number of pronounced extrema. Upon examination of rotation frequencies of fluid particles and the corresponding non-linear resonances, we have found a strong connection between these extrema and disappearance of the non-linear resonances. This disappearance phenomenon has been studied using the Poincare surface-of-section technique.