Direct numerical simulations of a cylinder cutting a vortex

Steven Soriano, Rodolfo Ostilla-Monico

Published 2024-01-10Version 1

The interaction between a vortex and an impacting body which is oriented normally to it is complex due to the interaction of inviscid and viscous three-dimensional mechanisms. To model this process, we conducted direct numerical simulations of a thin cylinder intersecting a columnar vortex oriented normally to it. We identified the various stages of the interaction, including the separation of the boundary layer and the generation of secondary vorticity that interacts with the primary vortex. By varying the impact parameter and the Reynolds number, we were able to distinguish the two regimes of interaction mentioned in the literature: the weak and strong vortex regimes. We found that low impact parameters, representing strong vortices, led to ejection and interaction of secondary vorticity from the cylinder's boundary layer, while high impact parameters, representing weak vortices, led to approximately inviscid interaction of the cylinder with the primary vortex through deformations. We did not find a significant effect of the Reynolds number in the overall phenomenology, even if larger Reynolds numbers lead to the formation of increasingly smaller and more intense vortex structures in the parameter range studied. Finally, we analyzed the hydrodynamic force curves on the cylinder, showing that intense forces could be locally generated for some parameter regimes, but that the average force on the cylinder did not deviate substantially from baseline cases where no vortex was present. Our results shed light on the underlying mechanisms of vortex-body interactions and their dependence on various parameters.