Swaying, intermixing, and stabilized vortex flow patterns behind bluff bodies controlled by plasma actuators: Flow past an oscillating circular cylinder

Study of oscillating circular cylinders is essential for various engineering applications , such as submarines, heat exchangers , bridges, and power lines, where controlling vortex-induced vibrations can enhance efficiency and reduce structural damage. In this study, a pair of surface dielectric barrier discharge (SDBD) plasma actuators , powered by alternating-current (AC) high-voltage sources, is employed to control the near-field flow around a circular cylinder oscillating at different frequencies and amplitudes. Particle image velocimetry (PIV) is used to analyze the near-field flow induced by the plasma actuators in a quiescent air environment. Simultaneously, a numerical model is developed to examine the near-field flow characteristics surrounding the oscillating cylinder at a Reynolds number of 1.5 × 10 4 . At a low reduced frequency ( f + = 0.098), the oscillating frequency of the incoming flow diminishes, making the reduced frequency dominant. This results in additional swinging motion within the shear layer vortex pair in the sweep region. Plasma-induced vortices on either side of the oscillating cylinder lead to a deviation from the cylinder's natural frequency, which reduces the likelihood of resonance and decreases drag. At a medium reduced frequency ( f + = 0.980), the reduced frequency dominates the shear layer vortex pairs, resulting in vortex intermixing. This reduces the lateral swinging in the sweep region, as intermixed plasma-induced vortices and the vortex street in the wake of the oscillating cylinder stabilize the flow. The vortex intermixing effectively reduces the maximum drag and suppresses lift fluctuations. At a high reduced frequency ( f + = 9.800), the synthetic jet induced by the plasma actuation acts as an aerodynamic virtual baffle, while wall-adhesive jets stabilize the separated shear layer of the oscillating cylinder. Stabilized vortices suppress maximum lift fluctuations and further reduce drag. The findings are categorized into three regimes: swaying, intermixing, and stabilized vortex regimes. By adjusting the plasma reduced frequency to guide the near-field eddy current field of the oscillating cylinder into the different regimes mentioned above, we provide a systematic strategy using one active flow control set to achieve the purposes of reducing drag, stabilizing lift, and avoiding vortex-induced resonance in the application scenarios of the oscillating cylinder.