Experimental investigation of the cylinder wake control at Re=1000 using plasma actuators

The control of the cylinder wake at Re=1000 by in-phase and out-of-phase plasma actuations is studied. The main objective is to investigate the role of the modified wake pattern symmetry induced by plasma actuation on vortex shedding suppression. Two dielectric barrier discharge (DBD) plasma actuators with momentum injection are utilized for unsteady excitation with duty cycle 50% for in phase actuation at natural shedding frequency while superharmonic actuations is applied for out-of-phase case. The symmetric wake structure is formed through in phase plasma activation while asymmetric vortex shedding is created using out-of-phase plasma excitations. To observe the wake structure modifications due to plasma actuation, the downstream velocity field is investigated by 2D particle image velocimetry (PIV) for no control and controlled cases at harmonic as well as superharmonic forcing frequencies. The results show a competition between symmetric and asymmetric vortex shedding modes. The symmetric wake structure induced from harmonic in phase excitation reduces the lift force while asymmetric flow pattern deduced from superharmonic out-of-phase actuation postpone the separation point and decreases the wake region. Both symmetric and asymmetric excitations reduce the circulation region however the in-phase DBD plasma actuation corresponding to symmetric wake pattern is more effective.

Keywords:

wake pattern , dielectric barrier discharge (DBD) plasma actuator , duty cycle , particle image velocimetry (PIV)