Laminar airfoil modification attaining optimum drag reduction by use of airfoil morphing

In this paper, the effectiveness of morphing a laminar airfoil's leading-edge through deformation in order to reduce the drag at the off-design angle of attack is herein investigated. The configuration of the airfoil was deformed under the structural restriction that the leadingedge is deformed while maintaining the girth of the deformed part and the configuration of the "wing box". The NACA 631-012 laminar airfoil was chosen as the original airfoil. The Reynolds number based on the original airfoil chord, was Re_c = 3×10⁶. Aerodynamic characteristics of the original and deformed airfoils have been investigated using a Viscous-Inviscid Interaction method. It is shown that the leadingedge deformation is effective in reducing the drag at the off-design angle of attack, in comparison to the original airfoil. The transition point has been estimated using a numerical method based on a linear stability theory. The deformation is an effective means to move the transition point aft on the airfoil, and the extension of the laminar flow area results in a reduction in the drag at the off-design angle of attack.