Resumo:
The stall is a well-know aerodynamic effect that consists of a lift abrupt fall due to the flow detachment from the body. Several studies were made in an attempt to suppress this effect, both to avoid air accidents and to improve aircraft aerodynamics and efficiency. This work presents numerical studies of viscous and incompressible Newtonian fluid flow on a pitching NACA0012 airfoil to analyze the dynamic stall delay and suppression. The boundary layer detachment control methods studied were with the introduction of slats, air jets, and suction in the suction region of the airfoil. For these studies, the COMSOL Multiphysics simulation program was used with the k-ω turbulence model and all simulations were carried out at the Heat Transfer Laboratory (LabTC) of the Federal University of Itajubá. The first study to suppress the dynamic stall effect was made by introducing slats to the airfoil, generating a stall delay and reducing the drag peak by 15.52%. In the second study, the implementation of blowing jets was carried out in three leading-edge positions with speeds varying from one to four times the flow speed. All cases with inflated jets there was a delay in the dynamic stall and for the cases with positioning of 2,5%𝑐 and 5%𝑐, where 𝑐 is airfoil chord, using 𝑈𝑖𝑛𝑠=4𝑈∞ the stall was tottaly suppress, with 𝑈𝑖𝑛𝑠 the inflation speed and 𝑈∞ the free-flow speed. The third study was aimed at adding a suction point in the upper region of NACA0012 where suction did not inhibit the dynamic stall, but made it possible to delay this effect. Qualitative and quantitative analyzes of the results were carried out through the pressure and velocity fields and the aerodynamic coefficients to demonstrate the delay and suppression of the dynamic stall effect. A validation study of the methodology used was also carried out comparing the results obtained with numerical and experimental results from other authors to demonstrate the good reliability of the methodology.
