Transition effects on flow characteristics around a static two-dimensional airfoil

Flows past a static NACA0015 airfoil are numerically investigated via Reynolds-averaged Navier-Stokes simulations at the Reynolds number 1.95 x 10(6), the Mach number 0.291, and the angle of attack (AoA) from 0 degrees to 18 degrees. Specifically, a one-equation local correlation-based transition model (gamma model) coupled with Menter's k-omega shear stress transport (SST) model (SST-gamma model) is employed to approximate the unclosed Reynolds quantities in the governing equations. Distributions of mean velocity and Reynolds stresses as well as typical integral quantities, such as the drag coefficient, lift coefficient, and moment coefficient, are calculated and compared with previously reported experimental data and present numerical data based on Menter's original k-omega SST model. It turns out that the SST-gamma model enables the capture of a laminar separation bubble (LSB) near the leading edge of the airfoil and shows significant advantages over the traditional "fully turbulent" models for the prediction of static stall. As the AoA varies from 0 degrees to 18 degrees, the flow regime is affected by different processes, i.e., flow transition, flow separation, and interaction between the LSB and the trailing-edge separation bubble, which, respectively, correspond to the linear-lift stage, light-stall stage, and deep-stall stage.