Asymmetric vortex pair induces secondary traveling wave vibration of a flexible cylinder from still water to incoming flow

As one of the fundamental problems in fluid mechanics, flow-induced vibration a flexible cylinder helps shed light on various complex fluid–structure interaction phenomena, such as coupling effect cross-flow and in-line motions relationship between external forces vortical wake patterns. This paper devised non-uniform in-flow condition (partially uniform flow partially still water) for cylinders experimental numerical conditions. Consistently, new phenomenon is observed different scale experiments simulations where secondary traveling wave excited from water part to inflow due positive energy input water. Furthermore, detailed visualization patterns around vibrating reveals that force sources are existence attached vortex pair with an uneven strength, which has been before rigid oscillatory or oscillating at Keulegan–Carpenter number 4 7.