Flow control of a D-shaped bluff body using different DBD plasma actuators

The control performance of a streamwise-oriented dielectric barrier discharge (DBD) plasma actuator, a set of plasma streamwise vortex generators (PSVGs), and a hybrid actuator of the plasma actuator and PSVGs on the reduction in bluff body flow separation, vortex-induced vibration (VIV), and wake fluctuation is experimentally investigated. Experiments are conducted in a low-speed and low-turbulence wind tunnel with a Reynolds number between 3 ×10³ and 1.2 ×10⁴ based on the diameter of a half circular cylinder. Particle image velocimetry (PIV) is used to obtain details on the flow fields over a short D-shaped bluff body. Force measurement is conducted to compare the reduction in drag and vibration oscillations using these three types of plasma actuators. The PIV flow fields show that all of the plasma actuators suppress the flow separation on the bluff body, narrow the size of the wake, and decrease the turbulence kinetic energy (TKE) level in the wake. This stable controlled vortex shedding system can reduce the effect of the natural frequency of the bending stiffness-dominated cylinder structure system, thus avoiding the occurrence of resonance in advance. The reduction in drag and lateral lift oscillation are studied by mapping the changes in force coefficients and fluctuations as a function of Reynolds number. A comparison of these plasma actuators shows that the hybrid actuator achieves best drag reduction, suppression of lift oscillation, and Kármán vortex shedding in the wake at low speed, because three-dimensional flow structures are generated on the surface of the bluff body that consequently enhance the mixing. The results suggest that PSVGs and ameliorative actuators are promising for wake flow control in bluff bodies at low speeds.