Effect of impinging wake turbulence on the dynamic stall of a pitching airfoil

Dynamically moving airfoils are encountered in helicopter rotors, wind-turbine blades, and maneuvering aircraft. A clearer understanding of how freestream disturbances affect the aerodynamic forces on pitching airfoils leads to improved designs. In the present study, the authors' recently validated spectrally accurate moving overlapping mesh methodology is used to perform a direct numerical simulation of aNACA0012 airfoil pitching with oscillatory motion in the presence of a turbulent wake created by an upstream solid cylinder. The global computational domain is decomposed into a stationary background mesh, which contains the solid cylinder, and a mesh constructed around the airfoil that is constrained to pitch with predetermined reduced frequency κ=0.16. Present simulations are performed with chord-based Reynolds number Re_c=44,000. Aerodynamic forces and vortex-shedding properties are compared between the pitching airfoil simulations with and without upstream disturbances. Power spectral density functions of the aerodynamic forces and moments are investigated to further determine the effect of a turbulent wake on a pitching airfoil.