<p>The Dielectric-Barrier-Discharge (DBD) plasma actuator is a highly efficient active flow control device, being widely recognized for its potential applications in boundary layer separation control. While many researchers have explored the practical implementation and performance of DBD plasma actuators in various aerodynamic contexts, the fundamental physical mechanisms governing plasma-induced flow control remain relatively under-explored. The present study utilizes numerical simulation to investigate the plasma-induced flow dynamics around a circular cylinder, whose configuration is selected due to its geometric simplicity and the prominent boundary layer separation that occurs due to its highly curved surface. The flow field is simulated by solving the Unsteady Reynolds Averaged Navier Stokes (URANS) equations while the plasma actuation effect is incorporated through a well-known mathematical model. In this study, two DBD plasma actuators are symmetrically installed on the left and right sides of the cylinder. The ambient air is set to be initially quiescent and the resulting flow field is driven entirely by the plasma. This research makes two primary contributions. First, the flow fields generated under duty-cycle actuation signals are simulated and validated against existing experimental data. Particular attention is given to the generation, evolution and propagation of vortex structures arising from different actuation modes. Second, a detailed analysis is conducted on how a time-varying plasma body force affects the distribution of pressure force, skin friction and momentum transfer.</p>