Retro lock-in in the wake-induced vibration of a pair of tandem cylinders in close proximity

An experimental investigation performed at moderate Reynolds numbers was set to study how a pair of tandem cylinders can be excited into flow-induced vibrations by different interference mechanisms as a function of longitudinal spacings varying from 2 to 10 diameters. Results showed that the downstream cylinder could develop vortex-induced vibration (VIV) caused by its own vortex shedding, wake-induced vibration (WIV) caused by a developed wake formed in the gap, and gap-flow-switching. A combination of these mechanisms appeared for cases under close proximity. For a specific spacing of 3 diameters, the vibration of the downstream cylinder was able to synchronize the vortex shedding from the upstream, fixed body. We call this mechanism "retro lock-in" since the vortex-formation process of a bluff body was governed by the dynamics of another body located further downstream.