Effects of Fineness Ratio on Flow Field of Axial Circular Cylinder

In this study, flow fields of the circular cylinder aligned to free stream were measured and dependencies of them on the fineness ratio (length to diameter, L/D) were investigated. All the tests were conducted under interference-free condition using a magnetic suspension and balance system. The velocity fields in the plane including the center axis of the cylinder were obtained by particle image velocimetry (PIV) under the condition of Re = 33,000 and 50,000 and L/D = 1.5 and 2.0, respectively, whereas the previous study shows that the flow separated at the leading edge reattaches at the position downstream 1.5 to 1.7 times the diameter and the drag becomes minimum in the case of L/D ∼ 1.7. As a result, fluctuation in the frequency close to that in the circumferential fluctuation in the previous study was observed. Furthermore, this phenomenon is observed in the case of L/D = 2.0 despite the occurrence of the reattachment. In order to investigate the relationship between aerodynamic force and flow field, synchronous measurement of flow field and aerodynamic force will be performed.