Vortex Interactions in Two-Dimensional Turbulence

Interactions of coherent vortices in decaying two-dimensional turbulence are quantitatively assessed. Direct numerical simulations are performed, and a tracking algorithm is implemented to autonomously identify vortex structures and track their evolution in time. Vortex properties such as circulation, area, vorticity, strain rate, and enstrophy are used to assess Individual interactions and their outcomes. Inelastic interactions such as merging and straining out, observed here in a field of vortices, are compared with those characterized by isolated asymmetric vortex pairs (Folz and Nomura, JFM 2017). The statistics of these interactions are interpreted in terms of their cumulative effects on the overall flow.