Direct Numerical Simulation Of DBD Plasma Flow Using Suzen Model

With the development of aeronautical technology, there is a higher demand of aircraftaerodynamic performance and engine efficiency. DBD (Dielectric Barrier Discharge)plasma flow control techniques, which has been a hot topic of Aerodynamics, couldplay a role in suppressing airfoil stall, enhancing compressor stability margin,improving turbine efficiency, controlling boundary layer flow separation and reducingaerodynamic noise. The direct numerical simulation is a valid method of exploring theflow mechanism. Direct numerical simulation of DBD plasma flow would be helpful forunderstanding the plasma actuators.The Suzen phenomenological model was used solving the electric force. By solvingthe Laplace equation and the Poisson equation, the potential and the charge densitycould be obtained. Therefore, the electric force was acquired. The calculating programused in this paper was OpenCFD2d, which was written by Li Xinliang. By augmentingthe terms representing the body force to N-S equations, a coupled program wasdeveloped, which could calculate the plasma flow. Firstly, the flow field induced by aDBD actuator in quiescent flow was calculated. The computational result wascorresponded with the experiment result, which proved that the grogram wasappropriate for the plasma flow simulation. Secondly, the simulations of the flow fieldon a flat plate induced by the steady actuators with different voltage, stream velocityand electrode gap were conducted. The following conclusions could be derived from thesimulations. The main effect of the plasma actuator is momentum injection to theboundary layer. The higher the voltage, the better the actuators perform. The streamvelocity and electrode gap do the reverse.Next, the situations induced by the unsteady actuators were investigated. Thetime-averaged and the instant flow fields were analyzed in detail. The followingconclusions could be derived from the simulations. The momentum injection of thesteady actuator is fiercer than that of the unsteady one. In the unsteady condition, themomentum transfer is much more quickly, the jet velocity decreases faster and the jetwidth spreads further. The effect of the unsteady actuator is not only injecting themomentum into the boundary layer but also generating a string of vortex cores, whosefunction is enhancing the momentum transfer between the main flow region and theboundary layer. Because of the existence of the velocity core array, there is a function ofentrainment-promotion acting on the fluid. Otherwise, the skin-friction coefficient inthe condition of unsteady actuator is smaller than that in the condition of steady actuator. At last, the conditions with the different frequency of the unsteady actuator werecalculated. While the frequency changes, the ability of the momentum injection keepsconstant. In the condition of lower frequency, the gap between vortex cores is wider, themomentum transfer is fiercer and the fluid parameters change more violent.