Case Studies of the Human Cardiovascular System - Computational Hemodynamics: Theory, Modelling and Applications - page 183

Fig. 7.2 Three dimensional
views of the stenosed carotid
bifurcation. Anatomical
geometry of the carotid
bifurcation is reconstructed
using MRI data, and output
in the STL format. Three
views of the patient specific
vessel are presented with the
labels ECA, ICA, and CCA
representing the external,
internal and common carotid
arteries respectively. We note
the location of the stenosis
at the ICA has a relatively
smaller cross-sectional area
compared to the ECA

bifurcation. Finally, three pieces of reinforced flexible plastic tubes were attached to
the inlet and outlet of the phantom as connectors to the flow loop in the PIV experi-
ment.

7.2.2 Computational Mesh Generation

After extracting the cardiovascular structure, the computational file can be saved
as an IGES, STL, or STEP to be cross-compatible with 3D modelling and mesh-
ing programs. The meshing procedure can begin by applying a simple unstructured
tetrahedral mesh all over which produces a single contiguous mesh. However for
easier post processing of local flow variables, the computational model may be
split into smaller sub regions during the CAD surface and volume generation stage,
prior to meshing. While the process of sub dividing the computational model into
smaller regions can be performed within some CFD packages, it is not always an
easy task, and therefore it is recommended to be performed in CAD packages that
have NURBS functionality.
For meshing of an atherosclerotic artery, surfaces were created and stitched to
create a computational mesh. An initial model with 129,182 cells was created and
refined by cell adaptation techniques that included refining large volume cells, cells
that displayed high velocity/pressure gradients and near wall refinements. This pro-
cess was repeated twice, with each repeat producing a model with a higher cell
count than the previous model. A model containing 786,712 mesh cells is shown
in Fig. 7.3 .
Prism meshes were used to resolve the thin boundary layers present. The first
mesh element, adjacent to the wall is a very thin layer and subsequent mesh elements