Hybrid inverse airfoil design method for complex three-dimensional lifting surfaces

A method is presented for inverse design of airfoils for complex three-dimensional wings in incompressible flow. The method allows for prescription of inviscid velocity distributions over different cross sections of the wing in a multipoint fashion. A hybrid approach is used to determine the shapes of the,sing cross sections that satisfy the design specifications. The airfoils forming the cross sections of the wing are generated using an inverse code for isolated airfoil design. A three-dimensional panel method is then used to obtain the velocity distributions over the resulting wing. The isolated airfoil velocity distributions are then used as design variables in a multidimensional Newton iteration method to achieve the design specifications on the wing. The method is particularly useful for complex geometries such as junctures, where three-dimensional and interference effects have to be accounted for in the design process. A key feature of the design method is a scheme to avoid using the panel method for sensitivity computations for the Newton iterations. This scheme not only results in significant reductions in computation time but also enables the integration of any readily available three-dimensional analysis code in executable form. Examples are shown to demonstrate the usefulness of the method.