Over the last decade, aircraft morphing technology has drawn a lot of attention in the\naerospace community, because it is likely to improve the aerodynamic performance and the versatility\nof aircraft at different flight regimes. With the fast paced advancements in this field, a parallel\nstream of research is studying different materials and designs to develop reliable morphing skins.\nA promising candidate for a viable morphing skin is the sliding skin, where two or more rigid\nsurfaces remain in contact and slide against each other during morphing. The overlapping between\neach two panels create a backward-facing step on the airfoil surface which has a critical effect on\nthe aerodynamics of the wing. This paper presents a numerical study of the effect of employing\na backward-facing step on the suction side of a National Advisory Committee for Aeronautics\n(NACA) 2412 airfoil at a high Reynolds number of 5.9 Ã?â?? 106. The effects of the step location on the\nlift coefficient, drag coefficient and critical angle of attack are studied to find a favorable location for\nthe step along the chord-wise direction. Results showed that employing a step on the suction side of\nthe NACA 2412 airfoil can adversely affect the aforementioned aerodynamic properties. A drop of\n21.1% in value of the lift coefficient and an increase of 120.8% in the drag coefficient were observed in\ncase of a step located at 25% of the chord length. However, these effects are mitigated by shifting the\nstep location towards the trailing edge. Introducing a step on the airfoil caused the airfoilââ?¬â?¢s thickness\nto change, which in turn has affected the transition point of the viscous boundary layer from laminar\nto turbulent. The location of the step, prior or post the transition point, has a noteworthy effect on the\npressure and shear stress distribution, and consequently on the values of the lift and drag coefficients.
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