The effect of an oscillating minute attachment on flow around circular cylinder

Inspired by the observation that minute rivulet oscillations can induce large-amplitude vibrations in stay cables, this study examined the influence of an oscillating minute attachment (MA) on aerodynamic forces and flow behavior around a circular cylinder. The MA consisted of a stainless-steel strip with controlled oscillation characteristics. The results demonstrated that the MA reduced the mean drag coefficient with pronounced effects at high Reynolds numbers, where it delayed flow separation and suppressed vortex shedding. The near-wall observations revealed the oscillating MA's capability to both promote boundary layer separation at its position and delay flow separation within oscillation cycles, forming a “low-velocity zone” with periodic variations. While the MA with small-amplitude oscillations captured flow separation effectively only at low Reynolds numbers, increasing oscillation amplitude successfully expanded the Reynolds number range for separation point control. At high Reynolds numbers with large-amplitude oscillations, aerodynamic forces and flow field were predominantly governed by the oscillating MA, with the wake exhibiting “contraction–expansion” flapping in boundary layers. The oscillating MA introduced its frequency into aerodynamic forces, suggesting potential applications for both vibration suppression in structural protection and vibration amplification for energy harvesting in cylindrical structures.