Study of the effects of fluid injection around a NACA 23012 airfoil

Flow separation is the main cause of loss of lift of aircraft’s wings at high angles of attack. Active flow control is nowadays an important subject of study to try to replace the widely used high lift devices on aircraft. This thesis studied, using CFD tools, one kind of active flow control : the continuous blowing located close to the leading edge, used to delay the boundary layer separation on the suction side of a NACA23012 airfoil. A 2D baseline airfoil at a Reynolds number of 5.10^6 was built, simulated using ANSYS Fluent software (using k-ω SST turbulence model and assuming compressible flow), and the results were compared to experimental data. Multiple configurations of the continuous blowing with different momentum coefficients, velocity ratios, injection channel’s widths, injection positions and injection angles were then built to assess their respective impact on the performances of the airfoil, compared to the baseline. An estimation of the power required to sustain the blowing was also provided. The baseline proved to accurately predict the lift of the airfoil. The simulations showed that the continuous blowing is useful to delay the flow separation of up to 4°, from the initial critical angle of attack of 16°, improving the performances of the airfoil at high angles of attack. The analysis showed that the velocity ratio is an important parameter, as too low values are actually harmful to the performances. While the angle of injection does not seem to play a major part, a optimal injection angle of 15° with respect to the airfoil’s surface was identified.