Effect of the presence of end plates and aspect ratio on the aerodynamic forces on circular cylinders in various flow regimes

Abstract

The presence of end plates and the cylinder aspect ratio significantly influence the aerodynamics of circular cylinders in wind tunnel tests. Although a large aspect ratio sufficiently reduces the effects of the free end and boundary layer of the tunnel walls, smaller end plates and aspect ratios are required for practical reasons. Thus, the aerodynamic characteristics of circular cylinders with small end plates and aspect ratios in the critical Reynolds number range are worthy of investigating because of the complexity of the flow states in these regimes. The wind pressure distribution on the circular cylinder is tested in the wind tunnel for Reynolds numbers of Re = (0.47–5.07) × 105, which cover the entire range of the critical Reynolds numbers. The effects of the existence of end plates and the aspect ratio of the cylinder on the aerodynamic forces and wind pressures at the middle of the cylinder and along the length of the cylinder in different flow regimes are discussed. The phenomenon of flow reattachment in the critical Reynolds number range is focused on to reveal the effects of the cylinder aspect ratio on the aerodynamics related to dry galloping for a cylinder with small end plates. The results show the necessity of including end plates and assuming a large aspect ratio to simulate a two-dimensional flow in the subcritical range. In the critical range, the less significant influences of the end plate diameter and cylinder aspect ratio strongly depend on the development of attachment along the length of the cylinder, which creates a three-dimensional flow and mitigates the spanwise correlation.