Corrections on the N-S code

[QLRO]

Dear Dokken,

Thank you for writing this excellent tutorial!

I would like to point out a few minor mistakes in your implementation. In particular, density rho is missing in several places. While this does not affect the results in your example since you have set rho=1, it may cause problems in general case.

I made the quick edits using github web interface. The same issue exists in the other N-S example too (also the theory part and the py files). I apologize for not having enough time to change them all locally.

P. S. For the DFG 2D-3 benchmark, I have not been not able to reproduce the entire 8s results by either simply increasing to 12800 steps over 8s or with lower dt (currently trying 1/3200). Have you been able to reproduce the entire 8s results? If yes, what settings did you use?

Best,

[QLRO]

I have some free time this weekend. I am happy to help you make the edits if it is ok.

[jorgensd]

@QLRO I observe that there are some stability issues after ~3.7 seconds. This is probably down to the mesh being to coarse (as the mesh depends on gmsh and its version, it might have slightly changed in the last two years). I will push a fix for this.

Some general comments to your PR:

1. Make sure that it is consistent everywhere.
2. Use jupytext to also update the .py file in the repo (this should happen automatically).

[QLRO]

I think that's everything I can find. Please have a look at the changes and let me know if I missed anything. Thanks!

[jorgensd]

Stability of the method has been improved in: https://github.com/jorgensd/dolfinx-tutorial/pull/99

[QLRO]

Dear Dokken,

Great! Thank you for your hard work!

I have updated both the notebook and the py file of the benchmark example to your improved code. Please see if there are any issues.

Best,