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CFD study of effects of boundary layer suction on transonic SC(2)-0714 airfoil performance

Abstract:

The complete understanding of the aerodynamics of wings and blades under transonic conditions represents a substantial challenge in the design of modern airplanes and turbomachinery. Transonic flow over airfoils may result in appearance of shock waves, which lead to increase in drag if not properly considered during the design stage. Therefore, it is a major challenge to design transonic airfoils such that potential appearance of shock waves is foreseen and negative drag effects are minimized. This paper presents the computational study of the SC(2)-0714 airfoil, focusing on its aerodynamics characteristics at Reynolds number of 35x106 and angle of attack of 2 and 10 degrees which are the most common operational conditions of transonic wings using this airfoil. The study was undertaken at free-stream Mach 0.72. The numerical simulation was conducted using the finite volume method on platform ANSYS CFXTM and solving the Reynolds- Averaged Navier-Stokes, mass conservation and energy equations. Mesh verification and model validation are presented. The latter is developed by using two different isotropic turbulence models: k- ω and Shear Stress Transport (SST) and the comparison of results with NASA experimental data to determine the best among the treated models. Thereafter, effects of local boundary-layer suction on shock wave strength and characteristics during transonic speed are analyzed for the two aforementioned angles of attack. Two suction slots were placed along the airfoil contour to determine their control effectiveness when compared to standard closed-contour airfoil. Suction slots were placed at the leading edge and in the middle of the upper camber of the airfoil with inflow in the normal direction to the surface. The slot length was 2.5 % of the chord with inflow velocity of 30%, 40% and 50% of free-stream velocity. Effects of suction slots were assessed on the wake region and by computing the resulting lift-to-drag ratio. Concluding remarks on the turbulence model and global aerodynamics performance of the airfoil are presented.