Numerical investigation of flow around one finite circular cylinder with two free ends

Flow around one finite circular cylinder with two free ends is of both fundamental and practical importance, without a detailed discussion yet. In this study a numerical investigation is performed to demonstrate its flow pattern and turbulent structure varying with the aspect ratio and Reynolds number. The results show that the drag coefficient decreases dramatically in comparison with the two-dimensional model and the horseshoe vortex around the mounted cylinder with one free end disappears. Instead, a pair of stationary recirculating eddies behind the cylinder is found in the axis direction at low Reynolds number. With the increasing of Reynolds number, four spiral vortices are formed by the interaction of the two three-dimensional separated flows from two free ends and the wake formed by the cylindrical surface. The separated flow recirculates to the backside of the cylinder and increases its local pressure. Additionally, an intersection zone and a backflow is found close to the end surface, caused by the up-wash flow from the sharp leading edge of the cylinder. Finally, a new relationship between the drag coefficient and the Reynolds number for one finite circular cylinder with two free ends is proposed.