Numerical study on flow-induced rotation of a circular cylinder-splitter plate body at low Reynolds numbers

Flow-induced rotation of a circular cylinder-splitter plate body at high Reynolds numbers has received substantial attention. This paper numerically investigates the flow-induced rotation of a circular cylinder-splitter plate body at low Reynolds numbers Re = 40～160, which has seldom been studied. Reynolds number and plate length effects on the rotation response, flow fields, and hydrodynamic coefficients are examined. Results indicate that the critical Re of bifurcation is proportional to the plate length. By increasing Re, the equilibrium oscillation angle θ_mean rises first and then arrives at a plateau; correspondingly, the root-mean-squared rotation angle θ_rms rises sharply from almost zero and then varies slowly with Re or remains constant. Generally, θ_mean varies inversely with the plate length, while the opposite is true for θ_rms; the onset Re of the sharp rise of θ_rms is larger for longer plates. The rotation frequency is proportional to Re. When the cylinder-plate body experiences the bifurcation with a strong oscillation, an individual vortex is locked on the upper side of the plate, forming a recirculation region. Additionally, two other vortices are shed respectively from the tail and the lower side of the splitter plate. When the body is static, three stable recirculation regions of different sizes are found above, below, and behind the splitter plate. When the bifurcation disappears, the splitter plate is flanked by two identical recirculation regions. Hydrodynamic coefficients of the cylinder-plate body are significantly smaller than that of a cylinder, mainly due to the efficient control of the splitter plate on the wake flow and the recovery of rear base pressure.