# Effect of NS-DBD Actuator Parameters on the Aerodynamic Performance of a Flap Lifting Device
## 2 Research Model and Grid Partition  
The NASA (national aeronautics and space administration) airfoil GA(W)-1 and its 29% flap, which are the widely used classic high lift multi-element airfoil, are selected as the numerical simulation study object. The airfoil is characterized by large thickness (the maximum thickness reaches 17% of the chord length), blunt leading edge, and trailing edge stall. In the meantime, the airfoil has a completely turbulent boundary layer, which can provide a larger lift coefficient without flow separation, and the shape of the flap gap has been optimized to better avoid flow separation. The outline of the airfoil GA(W)-1 and its flap are shown in Figure 1.  
The chord length of the wing is 0.3 m, the chord length of the fowler flap is 29% of the total chord length, i.e., 0.087 m, and the chord length of the main wing except the flap is 0.288 m. The far-field inlet flow velocity is selected as 10 m/s, the Reynolds number is \(0.19\times 10^{6}\), and the boundary thickness of the first layer is calculated as \(1\times 10^{-5}\) when Y+ is taken as 1. In this paper, a 10\({}^{\circ}\) flap deflection angle is selected as the research object, its parameters are defined by the orthogonal method, and the gap height is 0.075 m. Pointwise is used for grid partition, and after verifying the convergence of the grid, it is determined that the final amount of the grid is approximately 120,000. The grid structure is shown in Figure 2.  
The density-based solver, SIMPLE algorithm, and second-order upwind format in Fluent are used for numerical calculation, and the standard k-\(\varepsilon\) second-order model is used for the turbulence model. The Reynolds Averaged Navier-Stokes (RANS) model is used in this simulation.  
This study needs to calculate the unsteady simulation of 25 pulse periods, and it is a high Reynolds number problem, the workload of calculation and simulation is very huge. The final overall effect of NS-DBD on the airfoil is focus, and the specific impact and instability of NS-DBD convection field are not concerned, so Large eddy simulation (LES) and direct numerical simulation (DNS) methods are not very suitable, although they can more accurately simulate the flow field changes at every moment, but the overall effect and time equalization effect of LES, DNS, and RANS are equivalent. Therefore, the RANS model can not only save resources and time, but also get ideal overall results. In addition, the RANS model has been widely accepted in the existing unsteady NS-DBD numerical simulation research. [PERSON] et al. (2018) in order to obtain detailed flow field changes and get the goal consistent with the engineering test results in the numerical study of shock/boundary layer separation controlled by NS-DBD, the method of RANS and LES was combined. LES is used to solve the generation and evolution of vortices, then momentum is transferred to the boundary layer, and RANS is used to calculate the rest of the region. The final results are in good agreement with the experimental values, and RANS can get the phenomena in the engineering experiments, including reflux, flow field change, and other issues. The detailed transient change of separation bubble depends on the LES model. The RANS model cannot get all the unsteady contents of the flow field, but this  
Figure 1: The airfoil GA(W)-1 and its 29% flap.  
Figure 2: Mesh of the airfoil with a flap angle of 10\({}^{\circ}\).  
does not hinder its advantages in simulating large-scale problems and the rationality consistent with the engineering experimental results. Similarly, [PERSON] et al. (2018) used RANS model to study the influence of DBD on ACHEON nozzle model by numerical simulation. Finally, the effect of DBD on flow separation and vectoring nozzle is consistent with the three-dimensional experimental results. Therefore, it is reasonable to use RANS model to carry out the unsteady simulation in engineering application research.