This paper presents an experimental investigation on flow field induced by a dielectric barrier discharge (DBD) plasma actuator with serrated electrodes in still air to further improve its flow control effectiveness. For comparison, the actuator with widely used linear electrodes was also studied. Experiments were carried out using 2D particle image velocimetry. Particular attention was given to the flow topology, discharge phenomenon, and vortex formation mechanism. Results showed that a 2D wall jet was induced by the linear actuators, whereas the plasma actuators with serrated electrode introduced a series of streamwise vorticities, which might benefit flow control (e.g., enhancing the momentum transport in the separated boundary flow). In addition, the mechanism of 3D flow topology induced by the serrated DBD actuator was analyzed in detail.

Conclusion

This paper presents a study of the plasma actuator with serrated electrode. PIV experiments were carried out to study the flow topology, discharge phenomenon, and vortex formation mechanism, leading to the following conclusions:

(1) A 3D jet structure was induced by the SeDBD and verified through PIV measurements.

(2) As a consequence of two merging jets coming from two consecutive teeth, a synthetic jet exists within the plane aligned to a root plane.

(3) The jet within the plane aligned on a tip is relatively thin and similar to the jet induced by the linear actuator. At the tip of the serrated electrode, it is prone to inducing discharge with a locally strong electric field and relatively electric body force, thereby producing a relatively high induced velocity than any other part of the serrate tooth.

(4) Due to the shape of serrated electrode, SeDBD can spatially alter the generated local volume of plasma along the span of electrode, which is related to the local body force, and thus affected the flow field induced by SeDBD.

(5) An idealized conceptual model showing the flow topology induced by the plasma actuator with serrated electrode was proposed.

According to the presented results and analysis, we believe that the 3D jet induced by SeDBD may have certain applications in flow control, especially for flow separation suppression. Further studies are required to determine the control effectiveness of the SeDBD on flow detachment under free stream condition, as well as to investigate the relationship between the Reynolds number and tooth parameters (i.e., height and spanwise length). Another notable feature is the discharge characteristics at the tooth tip, which can cause overheating because of the locally strong electric field. This overheating may be useful for pulsed nanosecond dielectric barrier discharge, in which the main mechanism of impact is the energy transfer and rapid localized heating of the near-surface gas layer.

The results have been published on Sci. Bull. (2016) 61(6):481–487.