Influence of free-stream turbulence on the aerodynamic performance of a three-dimensional airfoil

Influence of free-stream turbulence on flows past a static three-dimensional SD7003 airfoil is numerically investigated via wall-resolved Large-Eddy Simulation (wall-resolved LES). The Reynolds number and Mach number are 60 000 and 0.2, respectively, with the angle of attack (AoA) varying from 4° to 14°. The purpose of this investigation is to clarify the effects of intensities and integral length scales of turbulence in the approaching flow on the aerodynamic performance of the airfoil. To this end, a synthetic digital filtering technique and a specific source term concept are employed to generate turbulent fluctuations within the incoming flow. It turns out that turbulence with higher intensity in the approaching flow may cause the variations in effective AoAs, which not only postpone flow development but also promote the diversity of flow classifications from an instantaneous point of view. Furthermore, it is shown that the integral length scale has significant and systematic impacts on turbulent fluctuations in the boundary layer. Larger integral length scales tend to result in higher levels of turbulence intensities, which thus induce larger separations at all AoAs.