Turbulence Simulations of Transonic Flows over an NACA-0012 Airfoil

Three different simulation approaches, namely unsteady Reynolds-averaged Navier-Stokes
(URANS), delayed detached-eddy simulation (DDES), and wall-modeled large-eddy
simulation (WMLES) are employed to simulate transonic flow over an NACA-0012 airfoil at
different angles of attack covering pre- and post-buffet-onset regimes. The freestream Mach
number is 0.75, and the Reynolds number based on the chord length is 10 million. These
conditions are the same as the wind-tunnel experimental conditions of McDevitt and Okuno
(1985). The NASA FUN3D solver is used for the simulations, which is an unstructured,
compressible flow solver. The URANS simulations are performed using the Spalart-Allmaras
(SA) model with the compressibility correction, the DDES predictions are based on the SA
model, and the WMLES are performed using an equilibrium wall-model. The unsteady RANS
simulations, only with the compressibility correction, predict the pre- and post- buffet
characteristics, which compare well with the experimental results. DDES results predicted a
lower buffet onset angle compared to experiment. The predicted shock locations are upstream
of the locations predicted by URANS. Using a fine grid in the spanwise direction, WMLES
predictions show buffeting consistent with the experiment.