Multipoint inverse method for multielement airfoil design

A multipoint inverse method has been developed for the design of multielement airfoils with desired velocity distributions in incompressible potential flow. The method uses an isolated-airfoil, multipoint, inverse code to generate each element of the multielement airfoil and a two-dimensional panel method to analyze the multielement airfoil. Through Newton iteration, the variables associated with the design of the elements in isolation are adjusted to achieve desired multielement velocity distributions. As the paper demonstrates, changes in the velocity distributions over the elements in isolation result in remarkably similar changes in the velocity distributions over the corresponding elements of the multielement airfoil. This similarity results in two key features of the design method: 1) the use of the isolated airfoil velocity distributions as design variables to achieve desired distributions over the multielement airfoil, and 2) the calculation of the gradient information for the Newton iteration during the design of the isolated airfoils rather than by several panel-method analyses, resulting in substantial savings in computation time. The method thus allows rapid interactive design of multielement airfoils with desired velocity distributions, which can then be analyzed using more computationally demanding viscous codes. Examples in the paper demonstrate the capabilities of the method.