Numerical study of the S809 airfoil aerodynamic performance using a co-flow jet active control concept

A Co-Flow Jet (CFJ) active flow control concept is implemented on the S809 air-foil and numerically investigated by using an in-house code based on Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model, aiming to systematically study the jet effect on the airfoil aerodynamic performance. The solver is validated by comparing the computed results with the baseline experiment measurement. The calculated aerodynamic force and moment coefficients agree fairly well with the experimental data, demonstrating the present solver can predict the attached as well as separated flows around the S809 airfoil with an acceptable precision. The CFJ jet-off geometry of S809 airfoil is simulated to study the jet channel effect on the baseline aerodynamic characteristic, showing that the jet channel could reduce the lift, increase the drag and cause an earlier abrupt stall at angle of attack (AoA) 16.24 degrees. The CFJ jet-on geometry is elaborately studied at three jet momentum coefficient levels, showing that co-flow jet has a significantly positive effect in increasing lift, stall margin, and drag reduction. For the cases with jet momentum coefficients 0.12 and 0.18, the total drag even becomes negative. It is found that the drag from pressure and shear stress of CFJ airfoil is larger than that of baseline, and it is the negative mass-flow-produced drag that significantly reduces the total drag to be below zero. For cases in which AoA are below a critical value (e.g., 20.15 degrees for the case with jet momentum coefficient 0.18), the power required to drive the jet flow decreases when AoA increases, demonstrating that the CFJ concept has an attractive advantage of minimum energy consuming. The present CFJ concept is proved to be a promising and effective active flow control method in the wind turbine application. (C) 2015 AIP Publishing LLC.