Variable arrangement. While the cell-centered variable arrangement is the one selected in OpenFOAM® and generally preferred with the FVM (Fig. 5.13a), vertex-centered [15] (Fig. 5.13b) variable arrangement methods have also been used. Two vertex-centered arrangements have been adopted resulting in either overlapping elements or a dual mesh, respectively. Because the dual mesh method is more popular, it is described next as a representative of vertex-centered methods.