The complex vortex dynamics behind a freely rotatable cylinder with an attached splitter plate of various lengths (0 < l/D < 1) is examined over a range of Reynolds numbers (25 < Re < 500) to cover laminar, transition and turbulent regimes. The objective of this work is to find an optimum plate length of splitter plate for controlling vortex shedding and minimizing the energy consumption. The Signed Distance Function based Immersed Boundary Method (SDFIBM) is used to study the complex dynamical interactions between the vortex shedding mechanisms from the cylinder and the tip vortex at the splitter plate tail’s end. The simulation results clearly demonstrate the optimum plate length and rotation angle for achieving minimum energy consumption at different Re. Further, the simulation results reveal the fundamental insights into vortex dynamics. Four different flow regimes are identified based on Re. In regime 1 (Re < 25), the rotation angle remains fixed at a stable equilibrium position . The symmetry breaking bifurcation onsets at Re =25 which belongs to regime 2 (25<Re<50). With increasing Reynold’s number (50 < Re < 300), a Hopf bifurcation is found when the cylinder-splitter plate system loses the stability to an oscillatory state. Because of the inherent symmetry in the equations of motion and the flow configuration, such oscillatory solutions also occur in pairs, each being confined in its oscillatory motion to either the upper or lower half of the symmetry plane; which one is realized in a given instance is determined by the initial orientation of the splitter plate. A sudden jump in rotation angle is observed in regime 4 (300 < Re < 500) which indicates the inception of multiple frequencies with different rotational amplitudes.
