Methods for the calculation of potential flow around thin bodies are well known and can be found in several publications. According to these publications the vortex lattice method (VLM) combined with the quasicontinuous-method (QCM) is most effective for membrane-like bodies with no aerodynamical thickness. The possible flow around edges of a membrane causes singularities which are considered using a cosinespaced vortex lattice. The structural membrane analysis with the finite element method (FEM) is also well known and has been applied to several problems of engineering. If the same mesh is used for both methods it is easy to combine the QCM and the FEM. However, a cosine-spaced FE-mesh makes no sense because it is not FEM problem-orientated. Therefore, until now, equidistant or nearly equidistant vortex lattices have been used to calculate the interacting flow and structure. They also cause unacceptable errors because they are not optimal for the VLM problem.
This paper describes a new method to reduce the errors of combined calculations of flow and structure. A FEM problem-orientated mesh out of improved finite elements is combined with a cosine-spaced vortex lattice. The method is called quasi-continuous-continuous (QCC) because the discrete forces of the VLM are transformed into a continuous membrane load. A set of numerical examples shows the excellent numerical performance of the QCC and the reduction of errors.