Generation of Computational Mesh for CFPD Simulations - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 92

Surfaces were then created and stitched up to create a computational mesh. An
initial model with 82,000 cells was created and used to solve the air flow field at a
flow rate of 10 L/min. The original model was refined by cell adaptation techniques
that included refining large volume cells, cells that displayed high velocity/pressure
gradients and near-wall refinements. This process was repeated twice, with each
repeat producing a model with a higher cell count than the previous model. Two
models, one containing 82,000 and the other containing 2.5 million cells, are shown
in Fig. 4.20 .
Fig. 4.20 Surface mesh of the first two sections S1 and S2 (anterior nose entrance region) from
Fig. 4.19 of the nasal cavity. a An initial coarse mesh. b After mesh refinement, the mesh count is
increased
Prism meshes are often used to resolve the thin boundary layers that are present in
wall bounded flows. The first mesh element adjacent to the wall is a very thin layer,
and subsequent mesh elements above the first mesh element become progressively
thicker until it the layers cover the distance of the boundary layer. As discussed earlier,
the mesh should change slowly and smoothly away from the domain boundary.
Figure 4.21 shows the application of a hybrid mesh that contains tetrahedral elements
inside the domain and prism layers along the surface or domain boundaries.