Three-dimensional numerical simulation of a vortex ring impinging on a circular cylinder

Abstract

A vortex ring impinging on a three-dimensional circular cylinder is studied using large eddy simulation for a Reynolds number based on the initial translational speed and diameter of the vortex ring. We have investigated the evolution of vortical structures and identified three typical evolution phases. When the primary vortex approaches the cylinder closely, a secondary vortex is generated and its segment parts move inward to the primary vortex ring. Then two large-scale loop-like vortices are formed, which evolve in opposite directions. Thirdly, the two loop-like vortices collide with each other, forming complicated small-scale vortical structures. Moreover, a series of hairpin vortices are generated due to the deformation and stretching of the tertiary vortex. The trajectories of the primary and secondary vortices and the relevant speeds of evolution are discussed. The total kinetic energy and enstrophy are investigated with the purpose of revealing the properties that are relevant to the three evolution phases. The boundary vorticity flux is further studied with the aim of analyzing the generation of vorticity and the connection with the pressure gradient on the cylinder surface.