This study analyzes the predicted flow over a NACA 0012 airfoil at varying angles of attack and three different Reynolds numbers. The ability of three different turbulence models to predict boundary layer separation and transition behavior is investigated. Particular interest is paid to prediction of the separation bubble that develops near the leading edge of the airfoil suction surface prior to stall. The FLUENT CFD solver was used to simulate turbulent airflow over the airfoil. The three turbulence models include the standard and realizable forms of the k-ε model, available in FLUENT, as well as a recently developed transition-sensitive k-ω model that was implemented into the solver using user-defined functions. By employing the new, transition-sensitive model, computed properties of the flow field were found to be closer to experimental data than results produced by utilizing built-in turbulence models. Most importantly, the new, transition-sensitive model predicts the occurrence of the separation bubble, which the other models are unable to predict. The new model also clearly reproduces the laminar, transitional, and turbulent flow that occurs over the airfoil.

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