The influence of collision angle on vortex reconnection during the symmetrical collision of vortex rings*

Limitations on the common vortex tube arrangements, namely the anti-parallel and the orthogonal configurations, constrain the parameter space of vortex reconnection studies to Reynolds number only in the literature. In a recent article by Hernandez and Reyes [Phys. Fluids 29, 103604 (2017)], the symmetrical collisions of three and six vortex rings in the incompressible laminar regime were numerically investigated. This particular configuration of vortex collision exhibits a similar vortex reconnection process to the common setups, but offers the ability to adjust the collision angle, which enables the investigation of the geometrical influence on the vortex reconnection phenomenon. We employ pseudo-spectral simulations to perform a parametric study by varying both the collision angle and Reynolds number for the symmetrical collision of vortex rings. We find that the collision angle does play a role in the reconnection process, where the reduction in the impact angle leads to increases in both the circulation transfer rate and the final circulation transferred to the collision plane. Furthermore, the circulation transfer mechanism is reported, which provides additional insights into the vortex reconnection phenomenon.