Model using curved shore boundaries show shape’s influence on vortex interactions

Among the complex fluid phenomena of interest in the open ocean, vortex interactions play a major role. While the shape of coastline can interact with these dynamics, only relatively few models have been applied to understand how ocean shore boundaries affect them. Coastlines are often curved, making it valuable to understand how shapes of these features affect the movement and interaction of ocean eddies. To this end, researchers report in Physics of Fluids a simple dynamic model of vortex interactions near a mimicked circular bay. The behavior of two interacting vortices highlight the complexity that can result from even simple configurations.

“To get a grasp of the problem we had to limit the initial conditions,” said co-author Eugene Ryzhov. Therefore, parameters were restricted to the simple condition of a vortex approaching along the shore toward another vortex trapped within a bay. In technical words, the authors formulated the model with the Kirchhoff-Routh stream-function. The shore boundary had a single configuration established for the model. Despite the high level of simplification, simulations in the model revealed that vortex interactions are inherently irregular and hard to predict.

This complexity only allowed for a rough classification of four outcome regimes for the two vortices, including one result where after interacting they leave the bay as a bound pair, leapfrogging one another. However, the outcomes clearly showed that along-shore propagating vortices can significantly affect dynamics of vortices entrapped in a bay, even when passing at significant distances. The results also indicate that vortex dynamics are not affected by boundaries themselves, but by the curvature of these structures.

Ryzhov plans to use this study as a first step in establishing more complex models with a greater number of parameters to enable examination of more realistic scenarios. In particular, Ryzhov wants to look at models that take the decomposition and new formation of vortices into account.

Source: “Interaction of an along-shore propagating vortex with a vortex enclosed in a circular bay,” by Eugene A. Ryzhov, Konstantin V. Koshel, Mikhail A. Sokolovskiy, and Xavier Carton, Physics of Fluids (2018). The article can be accessed at https://doi.org/10.1063/1.5009117 .