Objectives  In this paper, in order to study the flow characteristics and mechanism of three-dimensional flow around a circular cylinder of finite length,

  Methods  a numerical simulation using a Large Eddy Simulation (LES) and vortex structural classification technology is carried out, and the accuracy of the simulation is proven.

  Results  When analyzing the flow field, it is found that the length of the recirculation zone is smaller for a circular cylinder of finite length. In addition, the downstream from the free end can suppress the common phenomenon of Karman-Vortex-Street which leads to a loss of drag-coefficient. Compared with the fixed wall at the bottom, the free end surface has a higher influence on the onstream-wise velocity. The 'mushroom' vortex appears in pairs and two original points exist on the free end. The circular cylinder of finite length appears to be strongly three-dimensional with a lower drag-coefficient. Moreover, there is a tip vortex behind the free end and a horseshoe vortex in the cylinder-wall junction.

  Conclusions  The results of this paper give a relatively comprehensive description of the flow characteristics of a circular cylinder of finite length, and can provide useful references for relevant research.