Numerical Study of Stream-wise and Span-wise Nanosecond DBD Plasma Actuators Effects on Supersonic Flow Separation

The current paper aimed to investigate the primary control mechanism of various Nanosecond Dielectric Barrier Discharge (NS-DBD) plasma actuators on the Shock Wave/Boundary Layer Interaction (SWBLI). For this purpose, the effects of the NS-DBD actuator have been investigated on an M=2.8 supersonic flow numerically. The Reynolds Averaged Navier-Stokes (RANS) equations and  SST turbulence model were used as the governing equations to simulate the supersonic flow characteristics. The numerical simulation of the baseline flow (without plasma actuator) was verified using an investigation on wall pressure distribution and the size of SWBLI. Then, NS-DBD phenomenological model based on the energy deposition model in accordance with experimental data was applied to the baseline simulation. Moreover, various stream-wise and span-wise NS-DBD plasma actuator models were used to investigate the actuator effects on the studied flow’s low-density separation zone. Comparing the numerical results of the stream-wise and span-wise actuations revealed that both actuator types cause a momentum transferred to the flow, consequently decreasing the SWBLI region’s size and the boundary layer’s thickness. The results showed that the presence of the NS-DBD actuator increased the local temperature of flow over the insulated electrode. In this regard, a stream-wise NS-DBD actuator with a length of 90 mm upstream of the SWBLI increased the separation flow velocity by 33.7% and decreased the length of the separation region by 5 mm. Also, in this case, after 170 microseconds from the start of actuation, the size of SWBLI decreased by 4.2 mm. Therefore, it can be concluded that the stream-wise type of actuation was more effective in reducing the flow separation and SWBLI size than the span-wise type due to vortex generation into the inlet flow and suppressing the SWBLI region. The proposed NS-DBD actuators were mainly capable of applying the momentum to the boundary layer and reducing the velocity of separated flow in the SWBLI zone. The micro shock wave propagation through the flow associated with the NS-DBD discharge of the actuators can produce more effective high-speed flow control.