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 × 106, the Mach number 0.291, and the angle of attack (AoA) from 0° to 18°. Specifically, a one-equation local correlation-based transition model (γ model) coupled with Menter's k–ω shear stress transport (SST) model (SST–γ 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–ω SST model. It turns out that the SST–γ 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° to 18°, 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. [ABSTRACT FROM AUTHOR]