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

Abstract

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.

Flow Control over the Blunt Trailing Edge of Wind Turbine Airfoils Using Circulation Control

“…Actually, considering the aerodynamic analysis for CC implementation in Section 3.3, it is possible for the drag to reach a negative value if the Coanda jet is injecting at a sufficiently high momentum coefficient. It was also found in previous studies of co-flow jet control [37] and Coanda jet control [21] that the jet reaction force is the main contribution to the negative drag. Here, we would highlight this phenomenon by explaining more from a different perspective rather than just repeat the finding.…”

“…The present CFD code is validated in previous publications, including the S809 airfoil at different Reynolds numbers [37][38][39], the DU97-W-300 and DU97-Flatback airfoils [21], and the CC020-010EJ airfoil [21]. In Xu et al [21], the grid independency study was performed on the DU97-W-300 airfoil rather than the DU97-Flatback airfoil, and the grids for DU97-Flatback and CC airfoil are directly generated based on the scale of the chosen mesh for DU97-W-300 after the grid independency study.…”

Dynamic Stall Control on the Wind Turbine Airfoil via a Co-Flow Jet

“…More details about the governing equations and boundary conditions can be found in [21]. The dual-time stepping method [23] is adopted to advance the time-accuracy solution with pseudo time marching by means of the LU-SGS method [24].…”

“…The static prediction precision of the solver has been validated in a previous study [21] by comparing the numerical results of NREL S809 airfoil static characteristics with the experiment conducted in the Delft University of Technology [34]. Here, the dynamic prediction precision of the solver will be validated by comparing results with experiment conducted at Ohio State University (OSU) [22].…”

“…Moreover, the jet suction effect near the suction slot further enhances flow stability to remain attached to the surface at high angles of attack (AoA), thus inducing much higher circulation than conventional circulation control without jet suction. In a previous study, Xu et al [21] introduced this concept to wind turbine airfoil application, focusing on the static performance with active as well as inactive CFJ. The results showed that steady co-flow jet had a great positive effect in lift enhancement, stall margin expansion, and drag reduction.…”