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A Co-Flow Jet (CFJ) active flow control concept is implemented on the S809 airfoil and numerically investigated by using an in-house code based on Reynoldsaveraged 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 . 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 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. V C 2015 AIP Publishing LLC.

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Dynamic stall control of a S809 airfoil is numerically investigated by implementing a co-flow jet (CFJ). The numerical methods of the solver are validated by comparing results with the baseline experiment as well as a NACA 6415-based CFJ experiment, showing good agreement in both static and dynamic characteristics. The CFJ airfoil with inactive jet is simulated to study the impact that the jet channel imposes upon the dynamic characteristics. It is shown that the presence of a long jet channel could cause a negative effect of decreasing lift and increasing drag, leading to fluctuating extreme loads in terms of drag and moment. The main focus of the present research is the investigation of the dynamic characteristics of the CFJ airfoil with three different jet momentum coefficients, which are compared with the baseline, giving encouraging results. Dynamic stall can be greatly suppressed, showing a very good control performance of significantly increased lift and reduced drag and moment. Analysis of the amplitude of variation in the aerodynamic coefficients indicates that the fluctuating extreme aerodynamic loads are significantly alleviated, which is conducive to structural reliability and improved life cycle. The energy consumption analysis shows that the CFJ concept is applicable and economical in controlling dynamic stall.