The adopted mesh generation strategy belongs to the family of direct techniques in terms of working directly on the 3D surface. The triangular kernel, used to generate triangular meshes, is based on a widely known advancing front algorithm [11,12] with some modifications allowing for surface curvature and special front management . The basic idea of producing a quadrilateral is based on generating consecutively two adjacent triangles that will be merged to form a valid quadrilateral element. This implies the following modifications to the standard triangular kernel:
Since it is not guaranteed that the boundary of the surface (domain) is discretized into an even number of edges, an isolated triangle may remain in the mesh. Moreover, in the present algorithm, the formation of a quadrilateral is relaxed whenever it is too difficult or impossible to generate immediately the second triangle that could be merged with the first one into a valid quadrilateral. The resulting mesh is therefore of mixed nature containing potentially a large percentage of triangular elements.