Flow-induced coupled vibrations of an elastically mounted cylinder and a detached flexible plate

Abstract

A fluid multi-structure interaction (FMSI) study on flow-induced coupled vibrations of an elastically mounted cylinder and a detached flexible plate is carried out numerically at a constant $Re=100$ . The effect of a non-dimensional gap $G^{*}$ between the two structures, and reduced velocity $U_{c}^{*}$ , on the proximity-induced coupled flow physics and vibration characteristics of the system is presented. The FMSI system shows a two-state response: state 1 at larger gaps $G^{*}\geqslant 1$ , and state 2 at smaller gaps $G^{*}\leqslant 0.5$ . At larger $U_{c}^{*}$ , the plate encounters an oscillating wake flow in state 1, while it encounters onset of gap flow in state 2. Each state relates to distinct vibration characteristics of both the structures, with the cylinder showing a vortex-induced vibration response in state 1 and a galloping response in state 2. The amplitude response of the cylinder is governed by gap flow dynamics while that of the plate is governed by the cylinder–plate vortex-interaction dynamics. In addition to the constructive and destructive vortex interactions reported earlier, a partial vortex interaction is observed here. The vortex interactions in the near wake lead to distinct vortex-shedding patterns – 2S, C(2S), 2P and a novel C(2P) – in the far wake. Separate regime maps are presented for the various types of cylinder–plate vortex interactions and vortex-shedding patterns, correlated with the amplitude, frequency and phase difference of the coupled vibrations of the cylinder and plate. The vortex dynamics shows a strong correlation with the quantitative vibration parameters, indicating the strongly coupled multi-physics characteristics of the present FMSI system.