Flow-induced rotation of a circular cylinder with a detached splitter plate and its bifurcation behavior

The paper numerically investigated the flow past a circular cylinder with a detached splitter plate at a low Reynolds number of 100. This cylinder-plate body could freely rotate around the cylinder center as a whole. The examined gap ratio G/D between the rear base of cylinder and the leading edge of plate increases from 0 to 2. Numerical results illustrate the occurrence of the bifurcation of flow-induced rotation at 0 <= G/D <= 0.5 while it disappears at 0.55 <= G/D <= 2. In the bifurcation regime, the time-averaged offset angle (theta(mean)) decreases monotonically with increasing G/D. However, the bifurcation suddenly disappears as theta(mean) drops from 9.64 degrees at G/D = 0.5 to 0 degrees at G/D = 0.55. The root-mean-squared rotation angle theta(rms) increases approximately linearly at 0 <= G/D <= 1.6, and then jumps to a high value around 4.69 degrees at G/D = 1.7 and approximately remains the value as G/D further increases. The typical 2S (two single vortices alternately shed per cycle) shedding mode is observed in the wake. Nevertheless, four interaction behaviors are identified according to the position of vortices with respect to the splitter plate, including the bilateral, totally wrapped, partially wrapped and unilateral interaction patterns. The variation of hydrodynamic forces for the individual plate is similar to the whole cylinder-plate body, indicating the main contribution from the plate. Compared with the bare circular cylinder, distinct drag- and lift-reductions are achieved at G/D = 0.1-1.6 and 0-1.6, respectively. The maximum reduced percentages of drag and lift forces for the circular cylinder reach 12.04% and 82.35%, respectively.