Resumen del producto

Dynamics of two-dimensional barotropic flow around a rigid circular cylinder (representing an island) is studied. A base flow is considering as two concentric neighboring rings of uniform but different vorticity, with the inner ring touching the island boundary. For a given ratio of the vorticity in the rings, the governing parameters of the problem are the radii of the inner and outer rings scaled on the cylinder radius. In this two-dimensional parameter space, one can to determine analytically the regions of stability/instability for each mode of perturbation using a linearization of the problem. The non-linear, long-term evolution of the linearly unstable flow and the formation of new vortical patterns are studied numerically by conducting inviscid contour-dynamics simulations. Three different regimes was found for the instability flows: (i) the emission of vortical dipoles, which propagate away from the island; (ii) the emission of vortical dipoles, but which tend to form the new coherent multipolar configurations around the island; and (iii) an oscillating flow with periodic deformations of the inner ring. These regimes strictly depend on the parameters used (radii of the rings) but the number of the dipoles always equals to the number of the unstable mode. Since the coastal waters near islands are usually rich in chemical and biological material, while the vortex dipoles are normally quite robust, in the cases (i) and (ii), therefore, they can serve as carriers of the trapped material. The regime (ii) is the most likely for the flows with considerably nonzero net circulation.

Palabras clave: Isla en el océano barotrópico; estabilidad del flujo de chorro; vórtices dipolares.

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