On the locally continuous formulation of surface doublets

Exact (locally continuous) formulation of doublets and particularly rooftop basis functions based on unitary vector concept are presented. Basic properties of such a formulation are examined showing many advantages when compared with classical (approximate) formulation. In particular, in the case of rooftop basis functions based on exact formulation, the shape quality factor is defined and optimal shapes of quadrilateral patches are determined. If such quadrilaterals are used for modeling of general structures, the number of unknowns needed in the analysis is almost halved when compared with modeling by triangular doublets