Biomedical Engineering Reference
In-Depth Information
schemes were described. The different type of mesh element used (or its combination
of) determines whether the mesh can be set up as a structured or unstructured mesh.
Structured mesh has the advantage of smaller computational memory, and better so-
lution convergence, however it can be difficult to apply to complex geometries such
as the respiratory organs. An unstructured mesh on the other hand, has the ability to
conform onto complex geometries but requires more computational memory because
of the need to connect up an arbitrary number of neighbouring nodes.
Generating a quality mesh requires as much creativity as it does technical knowl-
edge. Therefore different techniques and strategies are presented for both structured
and unstructured mesh to provide the reader with some ideas that can be applied
to generating a quality mesh for different flow problems. Practical guidelines are
given which includes the importance of developing a coarse mesh to begin with for
initial flow field testing, and implementing a mesh independence test to ensure an
optimum mesh has been used.
Examples specifically related to haemodynamic flows were given in detail to accel-
erate the reader's understanding and experience into meshing. The next chapter pres-
ents case studies that wrap together all the theory presented in these first six chapters.
6.7
Review Questions
1. What are some of the benefits of a well designed grid?
2. What are some of the advantages of a structured mesh?
3. Why is it difficult to write CFD programs that involve a structured mesh for
complex geometries?
4. Discuss some of the advantages of an unstructured grid.
5. What are some of the difficulties that arise regarding programming of CFD prob-
lems for an unstructured mesh?
6. For the geometry below discuss how using a block-structured mesh has advan-
tages over a single structured or unstructured mesh.
7. Why is it better to start off with a coarse mesh when you first begin to solve a
CFD problem?
8. The stretched grid technique is an example of a local refinement technique that is
applied before a solution is obtained. What is one problem associated with this?
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