This paper presents the formulation of free mesh method and two approaches
of the method by incorporating quadrilateral elements. The approaches do no
t have any difference with the original free mesh method in their fundament
al algorithms, wherein local system equations with triangular elements are
created nodewise to create the global system equations, and their implement
ation is therefore very easy. The first approach creates quadrilateral elem
ents inside every triangular element, whilst quadrilateral elements are gen
erated outside every triangular element in the second approach. The results
of numerical examples indicate that the approaches improve the accuracy of
free mesh method, further opening the possibility for more improvement usi
ng an accurate quadrilateral element. Copyright (C) 2000 John Wiley & Sons,
Ltd.