Experimentally simulating the formation of polygonal patterns by systems of satellite vortices*

In this study, the interaction of point vortices arranged in different spatial configurations is investigated to gain fundamental insights into the role of satellite vortices on the formation of polygonal vortex patterns in a rotating fluid. Point vortices are synthetically created in experiments by using a 3 by 3 multi-position magnetic stirrer. The velocity fields at the free surface are recorded via Particle Image Velocimetry (PIV) measurement. Of interest is the evaluation of how each point vortex arrangement affects flow coherent structures, as extracted using Lagrangian Descriptors, and hidden flow structures, as extracted using proper orthogonal decomposition. This study will provide essential fundamental knowledge on the formation of polygonal vortex patterns and their modal transitions.