Computational Study of the Effect of Wall Geometry on the Transonic Buffet Envelope for a NACA0012
Transonic flow over a NACA0012 airfoil is simulated using Unsteady Reynolds-averaged Navier-Stokes (URANS) in Ansys Fluent to study the interaction of wall geometry and Mach number on the prediction of transonic buffet onset and offset. The wall boundaries are placed 1.5 chords away from the airfoil to match experimental wind tunnel conditions. The simulations were conducted on an unstructured two-dimensional grid with a region of quadrilateral cells around the airfoil to capture the boundary layer. Effect of the sidewalls or sidewall suction is not evaluated due to the two-dimensional grid. Three separate cases are considered—flat-wall, streamlined-wall, and farfield—to evaluate the impact of wall geometry on the prediction of buffet onset and offset across a range of Mach numbers between 0.72 and 0.80. The flat-wall case showed a convergence of buffet onset and offset at Mach 0.77, while the streamlined-wall case showed distinct onset and offset points until Mach 0.80. The farfield case showed distinct behavior compared to the other two cases, indicating that wall geometry has a major impact on predicting buffet behavior. The wall geometry also has an impact on the buffet peak-to-peak lift amplitude, with the flat-wall and streamlined-wall cases reporting similar amplitudes, while the farfield case amplitude was halved.
