Effect of Freestream Turbulence on Airfoil Limit-Cycle Oscillations at Transitional Reynolds Numbers

Numerical simulations are performed to study the effect of freestream turbulence on small-amplitude limit-cycle oscillations of an airfoil at transitional Reynolds numbers. A one-degree-of-freedom aeroelastic model was coupled with the National Research Council Canada in-house computational-fluid-dynamics code INSflow to perform unsteady Reynolds-averaged Navier–Stokes simulations for flows around a rigid NACA 0012 airfoil in free-to-rotate conditions. Without coupling a transition model, unsteady Reynolds-averaged Navier–Stokes computations based on the commonly used shear-stress-transport turbulence model could not capture the limit-cycle oscillations. This was expected because it had been previously shown that the limit-cycle oscillations were fed by negative aerodynamic damping due to laminar boundary-layer separation. A correlation-based transition model was then implemented in the code and applied to investigate the turbulence effects. The computed results confirmed qualitatively the experimental ob...