Analysis of core structures in unequal counter-rotating vortex pair interactions

The stretching kinematics and evolution of the finite cores of distinct counter-rotating vortices are investigated using implicit large-eddy simulations. These simulations prescribe Lamb-Oseen vortex pairs of unequal core size and strength as a time-varying inflow boundary condition using parameters from published experimental data. Prior experimental works suggest core stretching and jetting as potential causes of a precipitous vortex core pressure drop, which is examined in the absence of background turbulence and disturbances related to vortex generation that may be present in a real flow. However, simulations of in-phase vertical perturbations of these vortices at the inflow boundary indicate that a proper characterization of initial vortex perturbations is essential to achieve qualitative agreement of vortex pair growth against available experimental data. Investigations into the core dynamics are sought to improve the understanding of the underlying fluid mechanical events leading to this precipitous vortex core pressure drop observed in the secondary vortex.