Active Control of Low Reynolds Number Airfoil Flow by Implicit Large Eddy Simulation

At low Reynolds number, the boundary layer on the upper surface of the airfoil is easily separated from the leading edge due to its poor ability of adverse pressure gradient resistance. The separated shear layer may undergo transition to turbulence and flow reattachment and form a long separation bubble. The instability of this separation bubble affects the performance and the stability of the airfoil. Moreover, the detached turbulent layer may bring high skin friction. To cope with this problem, the flow characteristics of NACA0012 airfoil at low Reynolds number were studied by using implicit large eddy simulation. Based on the flow characteristics, the opposition control schemes were applied to the separation zone as well as the turbulent shear layer to improve the performance of the airfoil. Numerical results show that boundary layer becomes thinner and its ability to resistance the adverse pressure gradient is enhanced by using the opposition control scheme. Therefore, the separation zone is reduced effectively. At the turbulent zone, the normal transport of streamwise vortex is blocked and the development of the vortex structures is inhibited by the opposition control scheme, which effectively reduces the high friction of turbulence.