METHOD FOR THE CONSTRAINED DESIGN OF NATURAL LAMINAR-FLOW AIRFOILS

An automated iterative design method has been developed by which an ai rfoil with a substantial amount of natural laminar now can be designed while maintaining other aerodynamic and geometric constraints, Drag r eductions have been realized using the design method over a range of M ach numbers, Reynolds numbers, and airfoil thicknesses, The key featur es of the method are the compressible linear stability analysis code u sed to calculate N-factors; the ability to calculate a target N-factor distribution that forces the flow to undergo transition at the desire d location; the target pressure/N-factor relationship that is used to modify target pressures to produce the desired N-factor distribution; and its ability to design airfoils to meet lift, pitching moment, thic kness, and leading-edge radius constraints while also being able to me et the natural laminar flow constraint.