Vortex induced vibrations at high Reynolds numbers on circular cylinders

Vortex induced vibrations at high Reynolds numbers on circular cylinders

Reynolds Number is a fundamental parameter in defining vortex shedding from circular cylinders. Most of the studies of vortex induced vibrations are at moderate Reynolds Number values and there is a need to understand how the Reynolds Number affects these oscillations. An experimental set-up was created in the large test section to study vortex induced vibrations at high Reynolds Numbers. The circular cylinder model had a diameter of 0.72 m, allowing Reynolds Numbers up to 6E5 to be reached. By increasing the model’s surface roughness it was possible to reach the postcritical flow regime that produces coherent and highly organized vortex shedding. The set-up permitted the simultaneous measurement both of the instantaneous fluid force calculated integrating surface pressure distribution and the model oscillation. The research findings showed that, after the disappearance of coherent vortex shedding and consequent vortex induced vibrations in the Reynolds Number critical region, well-organized and coherent vortex shedding clearly reappears in the postcritical region with characteristics similar to those observed in the subcritical region.