A comparative study of Ac-dielectric barrier discharge versus Ns-dielectric barrier discharge plasma actuators in an incompressible turbulent mixing layer

A comparison between ac-dielectric barrier discharge (DBD) and ns-DBD plasma actuators is performed in a low-speed turbulent mixing layer to assess differences in their control mechanisms (momentum versus thermal). The mean flow response to actuation is matched for the two cases at a single downstream location to gauge scaling of relevant parameters (carrier frequency, energy per pulse, etc). The similarity between local behavior downstream is found to extend to the global flow, both in the mean and fluctuating components. However, the ns-DBD requires approximately six times more electrical energy to achieve the same control as the ac-DBD in this specific flow. An analysis of the flow field very near the splitter plate trailing edge sheds light on the difference in momentum versus thermal actuation mechanisms. A velocity deficit is observed for both actuators, but a thermal bump effect is evident in the ns-DBD case while a near surface jet is observed in the ac-DBD case.