An Empirical Model of Nanosecond Pulsed SDBD Actuators for Separation Control

Abstract

An one-zone inhomogeneous phenomenological plasma model is constructed based on the experiments and theoretical results to avoid the unaffordable computational cost of plasma-fluid models and kinetic models for Nanosecond pulsed Dielectric Barrier Discharge (NSDBD) plasma actuator used in flow control simulation. The present model is coupled to unsteady compressible Navier-Stokes equations as a source term in the energy equation. The coupled system is validated by predicting the flow induced by the NSDBD plasma actuator mounted on a flat plate and a circular cylinder in the quiescent air. The results show that the wave positions, wave speeds and wave structures are well predicted by comparing with experimental results. The present model is applied to investigate separation control over NACA0015 airfoil at a low and a high Reynolds numbers Re = 100, 000 and 1.15×10 at post-stall angles of attack by using Large-Eddy Simulation (LES) and Unsteady ReynoldsAveraged Navier-Stokes equations (URANS). At the low Reynolds number, main control mechanisms are the fast transition to turbulence promoted by the plasma actuation and the separation-bubble shedding at the pulse repetitive rate. At the high Reynolds number, only the URANS is carried out for the sake of reducing computational cost. The main control mechanism is that the spanwise vortices induced by plasma actuation bring outer high-energy fluid into near wall region and sweep along the upper surface. At low and high Reynolds numbers, the shedding frequency of the trailing-edge vortex is tuned to the pulse repetitive rate by shedding of separation bubbles and spanwise vortices, respectively. In conclusion, the present model can be used to investigate flow-control mechanisms and parameter study of NSDBD plasma actuator with trivial computational cost.