Journal of Conference Abstracts

Classification of Trajectories of Vortex Dipoles Emitted from River Mouths in Ocean

Vadim Pavlov (vadim.pavlov@univ-lille1.fr)¹ & Victor Goncharov (vigon@zbase.iaph.msk.ru)²

¹U.F.R. de Mathématiques Pures et Appliquées, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, 59655, France

²Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, 109017, Russia

We consider evolution of strong localized vorticity concentrations in a flow. Main purpose is the construction of possible scenarios, their classification and definition of geophysical parameters for really observable phenomenon of emitting dipole vortex structures from river mouths in open ocean. The analyses is made in the framework of 2D point vortex model with boundary conditions. Results of vortex dipoles dynamics are presented. Two scenarios depending on a possible mechanism of generating the similar vortex structures are analyzed. In the all scenarios the river inflow is simulated by a point source of constant potency.

1. The first case supposes that the dipoles have been formed in the river channel and then are ejected into the river mouth. The topological analysis of motion trajectories in neighborhood of the source shows that such process may be realized only in narrow mouths with half-angle less than (pi)/4. Two topologically various kinds of motion trajectories are possible for the vortex dipoles outgoing from the source. If the their energy is more than defined threshold value, the vortices move along open trajectories and abandon the river mouth. Otherwise the vortices move along closed trajectories without escaping from the river mouth.

2. The second scenario supposes that directly in the river mouth there is a some mechanism of generating the vortex dipoles. For example, such mechanism can be provided by a shore friction. However, whatever mechanism would be suggested its efficiency depends on whether or not they will have a time for forming before escaping from the river mouth. Like possibility is found for a wide rive mouth with half-angle greater than (pi)/4. In this case, for each angle of the river mouth there exists a threshold of vortex intensity below which the dipole vortices move along closed trajectories. Under the influence of a mechanism of intensification such vortices will became stronger and move along spirals until reach the threshold intensity. After that they lay on open trajectories and abandon the river mouth.