Experimental Study of Flow Separation over a NACA 0012 Airfoil at Low Reynolds Number with Freestream Turbulence

The influence of freestream turbulence on flow separation over a NACA0012 airfoil at low Reynolds number (Re=12,000) was investigated. Particle Image Velocimetry (PIV) experiments were performed at an angle of attack 0˚ ≤ α ≤ 15˚. Four grid turbulence generators of different sizes were used to introduce turbulence into the flow. PIV was used to roughly characterize turbulence levels of the flow. Results have shown there to be approximately 2%-4% freestream turbulence intensity provided by the turbulence generators. The wind tunnel baseline turbulence was approximately 0.1-0.3%. Results have shown that by introducing turbulence, vorticity in the boundary layer increased and stall was delayed. Flow fields for the baseline and different turbulence generators will be compared with the wing at varying angle of attack. Preliminary results have shown the flow around the wing in the no-turbulence case was separated at 8º, but the flow remained attached when a small amount of turbulence was introduced. These results have implications for the separation behavior and stall characteristics for small UAVs flying at low Reynolds numbers.