Generation of Computational Mesh for CFPD Simulations - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 97

4.6 Summary

The importance of generating a quality mesh in order to obtain reliable computational
solutions has been discussed. Also discussed was the hierarchy for a mesh element:
placing points, lines, faces, and then volumes, respectively, from the lowest to highest
topology. The type of mesh element used (or combination of elements) 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 solution 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 to
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. This includes the impor-
tance 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.
The mesh represents nodal points that are used to apply the set of fundamental
mathematical equations that represent the flow physics. These equations are referred
to as the governing equations of fluid flow or the Navier-Stokes equations. In the next
chapter, we present the governing equations and how they are derived to represent
the conservation principles related to fluid flow.

4.7 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
problems for an unstructured mesh?
6. What conditions and constraints apply if you had to use a structured mesh for
the outer wall geometry below? What about for an unstructured mesh? Discuss
the advantages and disadvantages for these cases.

inlet

outlet

surface wall