Suppression of vortex-induced vibrations of rigid circular cylinder on springs by localized surface roughness at 3×104≤Re≤1.2×105

Suppression of vortex-induced vibrations (VIV) of an elastically mounted circular cylinder in a steady flow is studied experimentally using localized surface roughness, called Passive Turbulence Control (PTC). PTC consists of two roughness strips with thickness on the order of the boundary layer thickness and placed parallel to the cylinder axis symmetrically with respect to the flow. The range of Reynolds number (3×104≤Re≤1.2×105) considered covers primarily the Transition to Shear Layer3, high-lift, flow regime. For the smooth cylinder, the broad synchronization range and higher peak amplitude in the upper branch and unstable oscillations in the lower branch are characteristic of VIV at higher Reynolds numbers and distinctive from those of lower Reynolds numbers. From the PTC-cylinder results with systematic variation of the PTC location, one strong-suppression zone and two weak-suppression zones are identified based on the location of the PTC. These zones are part of the Map that established the relation between PTC and Flow-Induced Motions in previous work. In the strong suppression zone, reduction of 30-80% is achieved while in the weak suppression zones reduction of less than 30% is achieved. Broad field-of-view flow visualization shows that smooth cylinder vortex structures change with PTC and between zones.