Step-26 3D calculation got errors after changing simulation size

[JT Hu]

Hi there,

I am playing with the heat equation model in Step 26. I first made the
changes below:
1. Changed the dimension to 3, and used a hyper-ball with energy input
at the core.
2. Decreased the initial global refinement and n_refinement to 1 and 3.
And the result looked fine (though boring).

Then I changed the size of the hyperball to 1e-6 since the real
system I am looking at is below micron scale. I decreased the size of
heated region to 1e-7 and decreased the time step to around 1 ns. Now
the result is strange: the temperature cross section shows alternating
strong and weak temperature at different time steps. The pattern also
became strange at time step 4. Any suggestion on why this is
happening? I tried different time step and refinement order but got
similar results. I attached the images and my code.

Best,
Jingtian

[Andrew McBride]

what happens if you choose your spatial units to be in microns and your time units to be be in ns? Adjust all constitutive parameters accordingly. My guess is that it’s a problem with scaling.

A

> --
> The deal.II project is located at http://www.dealii.org/
> For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en
> ---
> You received this message because you are subscribed to the Google Groups "deal.II User Group" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to dealii+un...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
> <step-26.cc><timeStep1.png><timeStep2.png><timeStep3.png><timeStep4.png><timeStep5.png><timeStep6.png><timeStep7.png><timeStep8.png><timeStep9.png><timeStep10.png>

[jingt...@gmail.com]

You are definitely right.. The problem was solved when I entered all physical parameters of just water.

Thanks!

—
Jingtian