Wake adjustment and vortex-induced vibration of a circular cylinder with a C-shaped plate at a low Reynolds number of 100

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The vortex-induced vibration (VIV) of a circular cylinder with a C-shaped plate arranged in its wake at a low Reynolds number of 100 is numerically investigated in this work using the direct numerical simulation. Four typical streamwise spacing ratios of 1.5, 3, 4.5, and 6 are examined in the computations that were carried out for the range of reduced velocities (Ur = 2–12). In terms of shear layer reattachment, wake interference, and vortex shedding, five flow regimes are identified, i.e., the extended-body regime, the front-face reattachment regime, the shear-layer combination regime, the one-row co-shedding regime, and the two-row co-shedding regime. The wake regime is sensitive to the spacing ratio and the reduced velocity. The switching of the flow regime occurs at the transition between the initial VIV branch and the lower VIV branch, accompanying a phase jump of 180°. Furthermore, the shift of the wake regime leads to the prominent fluctuation of the response amplitude. Among the five regimes, the two-row co-shedding regime has the maximum wake width, resulting in the maximum amplitude. In contrast, the shear layers are elongated in the extended-body regime and hence the prolongation of the vortex formation length, contributing to the suppression of VIV. The best suppression is achieved by placing the C-shaped plate behind the cylinder with a spacing of 1.5D, and the reductions in the lift force and the cross-flow amplitude reach 85.5% and 94.5%, respectively.