Inverse Airfoil Design Utilizing CST Parameterization

An inverse airfoil design process is presented that makes use of the CST parameterization method. The CST method is very powerful in that it can easily represent any airfoil shape within the entire design space of smooth airfoils. This makes it an ideal modeling technique for an inverse design process because accurate airfoil geometry treatment is required. The downfall of some inverse design processes is that they do not accurately handle the leading edge region due to large flow gradients and high curvature distributions. One way to account for this is by representing airfoils with smooth analytic functions, such as the CST method. The inverse airfoil design process presented is based on the relation between pressure residuals and the required airfoil shape change. The pressure residuals give the sign of the normal vector with which to modify the airfoil shape. The CST method is then used as the smoothing algorithm. The inverse design method is simple, accurate, and efficient. It is shown to accurately determine the airfoil geometry in both subsonic and transonic flows. Since this method simply examines pressure distributions to modify the airfoil shape, the flow solver can be kept separate from the inverse design process, allowing any fidelity flow solver to be used.