Generation of Computational Mesh for Haemodynamics Analysis - Computational Hemodynamics: Theory, Modelling and Applications - page 160

Fig. 6.8 A structured overlapping grid for a rigid blood cell in a vertical vessel

grids are that conservation is usually not maintained or enforced at block boundar-
ies, and the interpolation process may introduce errors or convergence problems if
the solution exhibits strong variation near the interface.

6.2.4 Unstructured Mesh

Geometries encountered in haemodynamics are typically non-orthogonal and do
not fit exactly in Cartesian coordinates of a structured mesh. An unstructured mesh
containing triangles or tetrahedra laid out in an irregular pattern (Fig. 6.9 ) is able
to fill the interior of curvilinear geometries. There are no coordinate lines that cor-
respond to the curvilinear directions ξ and η such as in a body-fitted mesh and the
cells are totally unstructured which makes it highly suitable for complex geometries
such as the arteries. However this comes at an expense of additional computational
costs in establishing a scheme to connect neighbouring grid points. In computa-
tional programming, new data structures (e.g. edge based, face based or cell based)
are needed to store the connectivity scheme which is complicated by the fact that

Fig. 6.9 Simplified 90° bend in the aortic arch filled with unstructured mesh comprising of a
triangular cells, and b polyhedral cells. c A hybrid mesh combining quadrilateral cells at the wall
boundaries and triangular cells in the centre