Numerical investigation of control of dynamic stall over a NACA0015 airfoil using dielectric barrier discharge plasma actuators

Abstract

The control of dynamic stall over a periodically pitching NACA 0015 airfoil using alternating current (AC) and nanosecond (NS) dielectric barrier discharge (DBD) plasma actuators is investigated by means of numerical simulation. This study employs a two-dimensional unsteady Reynolds averaged Navier-Stokes (URANS) approach to resolve the flow control process. The pulsed AC and NS plasma discharges are modeled by an empirical body force model and a sophisticated self-similar plasma formulation, respectively. Our study concentrates on the resolution of detailed control process of dynamic stall under DBD plasma forcing at two Reynolds numbers (Re) as well as on comparison of AC and NS plasma actuations in terms of control mechanism and authority. It appears that the dynamic stall without control at both moderate Reynolds number of Re = 2.5 × 105 and high Reynolds number of Re = 7.5 × 105 can be categorized into the so-called trailing edge stall. The trailing edge stall initiates with flow reversal near the trailing edge. Regarding the dynamic stall control, it is found that the jet flow produced by AC DBD or residual heat of NS DBD is responsible for inducing large-scale spanwise vortices, which, in turn, dominate the flow control. For the moderate Re flow, AC and NS plasma actuators have comparable performance and both achieve good control authority. However, for the dynamic stall control at high Re, the NS DBD achieves surprising success in enhancing lift of the airfoil and reducing aerodynamic hysteresis, whereas AC DBD nearly has no effect on the flow. It is found that the superiority of the NS plasma actuator over other control means is due to the thermal convection characteristic peculiar to NS plasma discharge. This characteristic makes the NS DBD plasma actuator more flexible in extending its influence region and acquiring a better control effect.