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  4. Results: Analyzing and Visualizing

Results: Analyzing and Visualizing

Finally start Gmsh with:

gmsh t3ad.msh

and

gmsh t3bd.msh

The results then are displayed:

Results after simulation of the mesh containing only prism elements – t3ad

Results after simulation of the mesh containing only tetrahedral elements – t3bd

What can be seen here, is that the even though the t3bd case has a finer mesh, with more elements, the results seem worse.

What could be seen in the command prompt, though, reveals what’s going on:

t3ad:

 m  :   147:  3.15E-05  ...


 *** CONVERGENCE ***   7.71197723E-04

This in contrast to t3bd:

  m  :   200:  1.60E-04  ...


 Number of requested steps done.          200

Simply put, this is caused by the latter mesh containing almost triple the amount of elements in comparison to the first. This requires more iterations to come to a proper solution.

In other words, the second simulation has not yet found a final solution.

Increasing Iterations

Now, let’s try to run the simulation some bit longer. Don’t forget to backup the files you want to keep, as a new simulation will overwrite the current output files.

Change line 2 in t3ad.din and t3bd.din to for example the following:

steps 1000 1.e-5

which makes sure the simulation will continue for a maximum of 1000 iterations, or until the final residu is lower than 1e-5. This will result in way longer simulation times, but in smoother results in both cases:

After 1000 steps – t3a

After 1000 steps – t3b

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