This work explores the aerodynamics of an airfoil oscillating in a uniform shear flow at chord-Reynolds number of approximately 1.2×10~4 using complementary two-dimensional Navier-Stokes computations and direct force measurements. A NACA 0012 airfoil is pitched harmonically about its quarter-chord, with 2° amplitude and reduced frequency up to 12, in positive-shear approach flow for non-dimensional shear values in the range 0.0 - 1.0. Previous steady airfoil results showed the development of negative lift at zero angle of attack in the presence of positive shear, opposite of the inviscid theory, and symmetry breaking in the wake. The negative lift magnitude and symmetry breaking in the wake increased with the non-dimensional shear rate. In the current results for an unsteady airfoil, the wake also exhibits symmetry breaking that leads to a deflected wake towards the high-speed side as the reduced frequency increases beyond the reduced frequency for an aligned vortex street. Interestingly, the presence of shear seems to have little or no effect on the average thrust and peak-to-peak lift and thrust fluctuation, while a prominent influence is seen on the average lift. The latter switches sign from negative to positive at a reduced frequency of approximately 3, and it increases in magnitude with both increasing non-dimensional shear rate and reduced frequency.
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