Page 148 - Process Modelling and Simulation With Finite Element Methods

Multiphysics 135

Now pull down the Mesh menu and select the Parameters option. We will
need to pack elements near the pellet for best resolution.

Mesh Parameters
Select more>>
Max element size near vertices: 6 le-4 7 5e-5 8 5e-5
Remesh
0 OK
There should be 1727 triangles yet again. Click the Re-Solve toolbar button.
Then refine the mesh to 6908 triangles. Again Re-Solve. The final solution
should look like Figure 3.13 below (cf. [9], p. 2-83):
lo3 Concentrat ion contours

Figure 3.13 Contours of concentration (reduced by disappearance in pellet phase)

3.5 Discussion

This chapter introduced the concept of multiphysics and then ran away from it.
One of the key messages from 53.3 and $3.4 should be to simplify the analysis of
your PDE system. For instance, in $3.3, multiphysics was not necessary due to a
change of variable to eliminate one PDE equation. Similarly, in $3.4,
multiphysics could be dealt with by sequential treatment of single physics. This
has the virtue of separating the work. It should be clear that the major difficulty
in solving the pellet reactioddiffusiodconvection problem was resolving the