与自由流方向对准的磁支撑等直圆柱体的无张线式测量
In order to avoid model support interference, the flow over cylinders of varying fineness ratio (length/diameter) aligned with the free stream were examined using a magnetic suspension and balance system. Thedrag coefficient variation of a right circular cylinder was obtained for a wide range of fineness ratios. ParticleImaging Velocimetry (PIV) was used to examine the flow field, particularly the behavior of the leading-edgeseparation shear layer and its effect on the wake. Reynolds numbers based on the cylinder diameter rangedfrom 5x104 to 1.1x105, while the major portion of the experiment was conducted at the ReD= 1.0x105. For themoderately large fineness ratio, the shear layer reattaches with subsequent growth of the boundary layer,whereas over shorter cylinders, the shear layer remains detached. Differences in the wake recirculation regionand the immediate wake patterns are clarified in terms of both the mean velocity and turbulent flow fields,including longitudinal vortical structures in the cross-flow plane of the wake. The minimum dragcorresponded to the fineness ratio where the separated shear layer reattached at the trailing edge of thecylinder. The base pressure was obtained with a telemetry technique. Pressure fields and aerodynamic forcefluctuations are also discussed.