The effectiveness of helical strakes in suppressing vortex-induced vibration of tandem circular cylinders

An experiment study of vortex-induced vibration (VIV) of two rigid cylinders equipped with and without helical strakes (pitch of 10.0D and height of 0.15D) in a tandem configuration was investigated at a critical spacing distance of 3.5D. Here, the cylinders were attached to a structural test rig, which would allow them to oscillate in the cross-flow direction only. The oscillation amplitude and frequency data were collected. Accordingly, the results revealed that in the case of the two bare cylinders, the amplitude response of the upstream cylinder was higher compared to the case of single cylinder usage. Furthermore, outcomes obtained confirmed that the helical strakes successfully reduced the oscillation amplitude for the upstream and downstream cylinders both, whereas they were ineffective if merely applied at the downstream cylinder. Hence, it can be concluded that the arrangement of the strakes influences the VIV suppression in the context of two-cylinder cases.