MULTIPOINT INVERSE METHOD FOR MULTIELEMENT AIRFOIL DESIGN

A multipoint inverse method has been developed for the design of multi element airfoils with desired velocity distributions in incompressible potential now. The method uses an isolated-airfoil, multipoint, inver se 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 ele ments in isolation are adjusted to achieve desired multielement veloci ty distributions. As the paper demonstrates, changes in the velocity d istributions over the elements in isolation result in remarkably simil ar changes in the velocity distributions over the corresponding elemen ts of the multielement airfoil. This similarity results in two key fea tures of the design method: 1) the use of the isolated airfoil velocit y distributions as design variables to achieve desired distributions o ver the multielement airfoil, and 2) the calculation of the gradient i nformation for the Newton iteration during the design of the isolated airfoils rather than by several panel-method analyses, resulting in su bstantial savings in computation time. The method thus allows rapid in teractive design of multielement airfoils with desired velocity distri butions, which can then be analyzed using more computationally demandi ng viscous codes. Examples in the paper demonstrate the capabilities o f the method.