The effect of leading-edge tubercles on airfoil aerodynamic performance

Abstract

In this research, the effect of leading-edge tubercles on the aerodynamic performance of symmetric NACA 0010 and high-cambered RAF-19 airfoils (2D wings) is numerically analyzed using the software ANSYS/CFX and the k-ɛ turbulence modeling at the Reynolds number of 2.5 × 105 . On the NACA 0010 airfoil, these tubercles cause to reduce the pre-stall lift coefficient while improving the post-stall lift coefficient. Besides, the airfoils with the largest wavelength and amplitude sizes of tubercles are shown to have the highest value of lift coefficient at post-stall angles of attack. However, on the modified RAF-19 airfoils, the performance improvements in the case of lift coefficient are only observed in the shortest wavelength and amplitude airfoils which could increase the CLmax, as well as the pre-and post-stall lift coefficient. On both airfoil types, the leading-edge tubercles cause the increase in drag coefficients on all the modified airfoils. The wall shear stresses and streamwise vortices results show that on all the modified airfoils, the boundary layer is energized by the counter-rotating streamwise vortices generated by the tubercles. In this research, the effect of amplitude, wavelength, and amplitude to wavelength ratio size of tubercles on the strength and interaction of the streamwise vortices and consequently their effect on the lift and drag coefficient of the modified airfoils are discussed. It is concluded that while increasing the amplitude of tubercles causes to increase the strength of the streamwise vortices, increasing the wavelength of tubercles causes to reduce the intensity of interaction of the streamwise vortices. Thus, between the modified NACA 0010 airfoils with close values of amplitude and wavelength ratio sizes, higher values of lift coefficient are observed at post-stall angles of attack on airfoils having larger-amplitude and wavelength of tubercles. In this research, the relation between the streamwise vortices and the separated flow regions generated behind the trough section of the modified airfoils at pre-stall angles of attack are also discussed. These separated flow regions are responsible for the lift coefficient reduction on the modified airfoils at pre-stall angles of attack. Moreover, in this study, the effect of spanwise bumps generated along the chord of the modified airfoils and their influence on the interaction of the streamwise vortices are discussed. These spanwise bumps are generated due to preserving the thickness to chord ratio while designing the modified airfoils.

Date	20 Oct 2022
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Louis Dufresne (Supervisor)