Improved adaptive quadrilateral mesh generation using fission elements

An improved technique for quadrilateral mesh generation using an approach based on fission elements is presented. Considerable work has been carried out by Zhu et al. [Zhu, J. Z., Zienkiewicz, O. C., Hinton, E. & Wu, J., A new approach to the development of automatic quadrilateral mesh generation. Int. J. Numer. Meth. Engng, 1991, 32, 849-866] in applying the advancing front technique to quadrilateral mesh generation. In this paper more details of the specific characters of quadrilateral elements and an improved mesh generation technique in which the final quadrilateral elements are accurately generated according to element size parameters, are presented. A new kind of transition element called fission elements are used in this quadrilateral element generation technique. These elements are used when two subfronts which both have an odd number. Active sides are formed after two triangles have been generated and combined to form a quadrilateral. This avoids having to add an extra constraint during the mesh generation and guarantees that the quadrilateral mesh generation is as easy as triangular mesh generation. Some new techniques for quadrilateral element mesh enhancement are proposed. All of these are demonstrated by a variety of examples.