Numerical investigation of flow induced by plasma actuators around a circular cylinder in quiescent air under duty-cycle actuation

The flow induced by a pair of Dielectric-Barrier-Discharge (DBD) plasma actuators symmetrically-mounted on a circular cylinder in quiescent air is simulated by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. A new body-force model for the plasma actuator is developed, which yields significantly improved agreement with experiments. In addition to velocity and vorticity fields, the computations provide time-instantaneous and time-averaged pressure field and pressure and skin friction distributions over the cylinder, which have not been available from existing experiments for this problem. The computational results are analyzed to reveal the relations between the plasma body force, pressure field, velocity, vorticity, forces on the cylinder, and momentum imparted to the flow as they impact the flow control effectiveness for different duty-cycle ratio and frequency of the plasma actuation input. A pair of cumulative vortices is discovered outside the experimental measurement window for the first time by the computations. Regardless of the level of duty-cycle frequency and the detailed near field vortex patterns, the vortices appear to eventually accumulate some distance downstream of the cylinder and move very slowly downstream. The present study is of direct relevance to problems involving vortex shedding and noise production from many circular-shaped aeronautical and civil structures. It helps to provide the necessary fundamental understanding of the flow physics and guidance for future design and optimization of DBD plasma actuators for flow control.