Fix NS-VOF stong residual formulation #1180

hepap · 2024-06-26T20:24:49Z

Description

The term associated with the viscosity jump in the strong residual for the NS-VOF assembler added in PR Add missing VOF term in the strong form of the residual #1149 led to a ill-posed formulation in phase change cases where the solid is represented by a highly viscous fluid. Hence, we don't consider this term in the current formulation.
There was no appropriate application test for lpbf/phase change with vof cases that could have allowed us to identify this ill-posed formulation prior to the merge of PR Add missing VOF term in the strong form of the residual #1149.
The LPBF benchmark example prm files were almost up to date, but did not exactly matched the one we used to generate the benchmark results. The mesh files were missing from the repo.

Solution

This PR removes the term associated with the viscosity jump.
A new test is now included to avoid future mistake in lpbf/phase change with vof cases.
LPBF benchmark example prm files were modified and are now up to date with the current working version. The mesh files are now available in the repo.

Testing

The new test simulate the lpbf benchmark case using the extra-extra-coarse mesh. Temperature statistics and mass conservation monitoring are the outputted metrics (to track both the change in HT and NS-VOF solvers).
Other NS-VOF tests were updated, and results for those tests returned to their previous values (or almost with small differences).

Documentation

No modification in the documentation.

Miscellaneous (will be removed when merged)

I guess the tests will fail because of the CI issue. I have still opened the PR since the formulation won't change and I will update the restart of the new test when I have updated my P4est version :)

Checklist (will be removed when merged)

Code related list:

All in-code documentation related to this PR is up to date (Doxygen format)
Lethe documentation is up to date
Fix has unit test(s) (preferred) or application test(s)
The branch is rebased onto master
Changelog (CHANGELOG.md) is up to date
Code is indented with indent-all and .prm files (examples and tests) with prm-indent

Pull request related list:

Labels are applied
There are at least 2 reviewers (or 1 if small feature) excluding the responsible for the merge
If this PR closes an issue or is related to a project, it is linked in the "Projects" or "Development" section
If the fix is temporary, an issue is opened
The PR description is cleaned and ready for merge

blaisb · 2024-07-01T23:16:12Z

The debug test still seems to crash?

AmishgaAlphonius · 2024-07-01T23:31:27Z

The debug test still seems to crash?

It's a bit weird, the load from a checkpoint function for the triangulation has an assertion that checks if all cells are at the same level of refinement. In Release there is no issue, but in Debug, it crashes because of this. I tried it locally also and I had the same issue. Is it that assertions are only checked on Debug?

source/solvers/navier_stokes_vof_assemblers.cc

CHANGELOG.md

blaisb · 2024-07-02T07:48:33Z

The debug test still seems to crash?

It's a bit weird, the load from a checkpoint function for the triangulation has an assertion that checks if all cells are at the same level of refinement. In Release there is no issue, but in Debug, it crashes because of this. I tried it locally also and I had the same issue. Is it that assertions are only checked on Debug?

You need to make sure the restart files does NOT refine the triangulation. Generally this is the case for all the solvers (we do not do mesh refinement when we are reading a restart file), however we don't have any restart tests for VOF I guess,so maybe this issue was there all along. You can check a restart with any VOF cse in the debug to see if that's the issue.
But otherwise, the triangulation/ mesh must have the same properties as the one used in the restart (aka the coarse grid has to be the same)

Assertions are not run in DEBUG mode, so that it works in release does not mean anything.

blaisb · 2024-07-02T07:50:09Z

applications_tests/lethe-fluid/heat_transfer_vof_lpbf_benchmark.mpirun=1.output

+Running on 1 MPI rank(s)...
+   Number of active cells:       16
+   Number of degrees of freedom: 75
+   Volume of triangulation:      0.36
+   Number of thermal degrees of freedom: 25
+   Number of VOF degrees of freedom: 25
+Initial refinement in box - Step  1 of 3
+   Number of active cells:       40
+   Number of degrees of freedom: 165
+   Volume of triangulation:      0.36
+   Number of thermal degrees of freedom: 55
+   Number of VOF degrees of freedom: 55
+Initial refinement in box - Step  2 of 3
+   Number of active cells:       88
+   Number of degrees of freedom: 339
+   Volume of triangulation:      0.36
+   Number of thermal degrees of freedom: 113
+   Number of VOF degrees of freedom: 113
+Initial refinement in box - Step  3 of 3
+   Number of active cells:       268
+   Number of degrees of freedom: 942
+   Volume of triangulation:      0.36
+   Number of thermal degrees of freedom: 314
+   Number of VOF degrees of freedom: 314


This part should not be happening in a restart file. Maybe this option just has neverbeen tested with a restart. IF we are restarting, we should not do any mesh adaptation :)

hepap · 2024-07-02T13:08:02Z

I will fix the restart with the box refinement feature on another branch, and I will come back to this PR so that it stays a coherent PR.

hepap · 2024-07-02T16:07:42Z

So I removed the box refinement for the new test in this PR, and I fixed the restart problem with box ref in PR #1184.

This PR (#1180) can be merge before PR #1184 (I added a test in PR #1184 to verify restart with box ref).

blaisb · 2024-07-02T20:35:49Z

@hepap can you rebase? Then this will be ready to go :)

AmishgaAlphonius

Great work Hepap! Everything looks good to me! Thanks for the fix! :)

blaisb

two minor things after rebase and this is ready to merge :)

applications_tests/lethe-fluid/CMakeLists.txt

hepap requested review from blaisb and AmishgaAlphonius June 26, 2024 20:30

hepap added the Ready for review label Jun 26, 2024

PierreLaurentinCS self-requested a review June 26, 2024 20:32

hepap added WIP When a PR is open but not ready for review and removed Ready for review labels Jun 26, 2024

AmishgaAlphonius force-pushed the fix_NS-VOF_strong_res branch from ca84a0b to f2c8ea2 Compare July 1, 2024 16:35

AmishgaAlphonius reviewed Jul 1, 2024

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blaisb reviewed Jul 2, 2024

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hepap added Ready for review and removed WIP When a PR is open but not ready for review labels Jul 2, 2024

AmishgaAlphonius approved these changes Jul 2, 2024

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blaisb approved these changes Jul 2, 2024

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hepap and others added 11 commits July 3, 2024 14:36

Remove viscosity jump term from NS-VOF strong res

8cc8e17

Update application test

14ff213

Add prm file for new lpbf test

ca78ac9

Remove term from rhs and non-newtonian assemblers

cf3bd12

Remove unused variables

f358aff

Add restart for lpbf application test

2b3355e

Update test

70877e2

Update change log

9ea4ecb

Add restart generator

4c08b95

Update restart with p4est 2.3.6

aaaac40

Update benchmark example prm files

3543f0d

hepap added 7 commits July 3, 2024 14:40

Update change log

f6f85b0

Add restart for lpbf application test

e35f7fc

Remove box refinement for the new test

ace253b

Apply comments from code review

209d547

Update changelog date

7b54bee

Apply comments for code review

ded6484

Update test after rebase

f30ab60

hepap force-pushed the fix_NS-VOF_strong_res branch from 56bbb85 to f30ab60 Compare July 3, 2024 19:10

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Fix NS-VOF stong residual formulation #1180

Fix NS-VOF stong residual formulation #1180

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Fix NS-VOF stong residual formulation #1180

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Fix NS-VOF stong residual formulation #1180

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hepap commented Jun 26, 2024 • edited Loading

Description

Solution

Testing

Documentation

Miscellaneous (will be removed when merged)

Checklist (will be removed when merged)

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hepap commented Jun 26, 2024 •

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blaisb commented Jul 2, 2024 •

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