Combined effect of bending stiffness and streamwise length of the attached flexible splitter plate on the vortex-induced vibration of a circular cylinder

A flexible splitter plate attached to the rear stagnation point of a circular cylinder is applied to control the vortex-induced vibration. The influence of its bending stiffness on the control effect is experimentally investigated for two streamwise lengths of 1D and 2D (D is the cylinder diameter). Five dimensionless bending stiffnesses are selected: 0.979 (P1), 3.123 (P2), 6.797 (P3), 23.087 (P4), and 47.484 (P5). The characteristics of cylinder vibration, flow field, lift, and plate dynamics are synchronously studied. The results show that the effect of the bending stiffness depends on the streamwise length of the plate. For the flexible splitter plate of 1D, the best suppression effect of cylinder vibration is achieved for the P2 case, where maximum vibration amplitude is reduced by 93%, while the galloping-like vibration is excited for P4 and P5 cases. According to the analysis of the plate dynamics and the wake development, a large plate vibration is expected to suppress the galloping-like vibration. The bending stiffness affects the vibration state of the flexible splitter plate, and consequently, the wake vortex development and dynamic response of the cylinder are changed. For the flexible splitter plate of 2D, the vibration amplitude response of the cylinder can be divided into three categories based on the variation of amplitude versus the reduced velocity. For P2-P5 cases, a beneficial phenomenon that a frequency branch is larger than the natural frequency occurs.