Numerical Simulation of the Flow around NACA0018 Airfoil at High Incidences by Using RANS and DES Methods

In this work, the flow around the NACA0018 airfoil with a wide range of attack angles was investigated based on the open-source computational fluid dynamics (CFD) platform OpenFOAM. Two numerical methods, Reynolds-averaged Navier-Stokes (RANS) and the detached eddy simulation (DES), were employed. Under the premise of a grid convergence analysis, the computed lift and drag coefficients were validated by the available experimental data. The pressure distribution, the complex flow mechanisms of the airfoil under the attached flow regime, the mild separation flow regime, and the post-stall flow regime, combined with the shedding vortex structures, streamlines, and vorticity distributions, are discussed. From the numerical results, it can be seen that the DES computation presents a better accuracy in the prediction of the lift and drag coefficients, with a deviation less than 10% at the largest angle of attack. Meanwhile, it also presents remarkable improvements in capturing the local flow field details, such as the unsteady separated flow and the shedding vortex structures.