Vortex dynamics and flow-induced vibration of a rounded-square cylinder with a detached splitter plate

For flow-induced vibration of a rounded-square cylinder under the effect of proximity interference by a stationary splitter plate downstream, a numerical study is presented for various corner-radius R(0.1−0.5), reduced velocity U*(2−12.5), cylinder-plate gap G*(0.3,2.0), Reynolds number Re = 100, mass ratio M*=1, damping coefficient ζ=0.005, plate-length L*=1, and plate-thickness t*=0.05. For various R, a vortex-induced vibration (VIV)-type of amplitude response is observed at G*=2.0, while a galloping-like response is shown for the smaller G*=0.3. For the VIV response, the sharpness of the cylinder (decreasing R) leads to a vibration-suppression and a narrower VIV lock-in region. For the galloping response, the decreasing R leads to a marginal increase in the cylinder amplitude A* and a significant decrease in frequency f* of vibration. Destructive and partial interactions of the cylinder–plate vortices are found in the near-wake, whereas in the far-wake, vortex-shedding patterns are affected by the rounded corners of the cylinder, leading to six different types of patterns. The vortex interaction, vortex shedding, and amplitude response are found to be inter-related to each other—examined with the help of regime maps for the various modes of vortex interactions and vortex shedding. The downstream splitter plate proximity-induced transition—from the VIV-to-galloping amplitude response—leads to an enhancement in the amplitude of vibration, which is larger for a sharper rounded-square cylinder as compared to that for a circular cylinder.