Differences between dielectric barrier discharge plasma actuators with cylindrical and rectangular exposed electrodes

Surface dielectric barrier discharges (DBDs) used as plasma actuators can induce significant time-averaged forces in nearby neutral gases. For single-barrier actuators (one electrode insulated) these forces are dependent on the geometry of the exposed electrode. We demonstrate that using thin cylindrical exposed electrodes can increase the induced force by several hundred percent compared with an actuator with a rectangular exposed electrode of the same thickness. This difference is due almost exclusively to the extent of the exposed electrode in the same direction as the gap between the two electrodes, which tends to be much longer for actuators constructed with rectangular exposed electrodes. The exact shape of the electrode cross-section plays no role. In addition, using an intensified digital camera we observed a new filament-free plasma that occurred only in discharges with exposed electrodes smaller than approximately 0.15 mm in diameter. These discharges spent an increasing fraction of the applied voltage period in this mode as we reduced the exposed electrode diameter. The mode shared several characteristics with a positive corona, and was partially responsible for a decrease in the electrical power used by these discharges.