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setting eb2.small_volfrac can introduce inconsistencies in EB data #1450

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darylbond opened this issue Oct 13, 2020 · 2 comments
Open

setting eb2.small_volfrac can introduce inconsistencies in EB data #1450

darylbond opened this issue Oct 13, 2020 · 2 comments

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@darylbond
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In my implementation, setting eb2.small_volfrac triggered a situation where the boundary normal provided by ebfactory->getBndryNormal() did not correspond with the associated face area fractions given by ebfactory->getAreaFrac(). This lead to non-conservative flux calculation when the area fraction was used to calculate the cell divergence while the boundary flux was calculated using the provided boundary normal. This situation can obviously be avoided by calculating the boundary normal from the area fractions.
@asalmgren asalmgren mentioned this issue Oct 13, 2020
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@asalmgren
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Thank you for pointing this out!

PR #1451 should fix this -- if you have a chance could you check that it fixes the case you have observed?

WeiqunZhang pushed a commit that referenced this issue Oct 14, 2020
@asalmgren
Fix when small_volfrac is used -- we need to adjust the data in cut c… (
5843b83 
#1451)

Fix when small_volfrac is used -- we need to adjust the data in cut cell neighbors as well as regular neighbors

This addresses  issue #1450

## Checklist

The proposed changes:
- [X] fix a bug or incorrect behavior in AMReX
- [ ] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX users
- [ ] are described in the proposed changes to the AMReX documentation, if appropriate
@darylbond
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darylbond commented Oct 26, 2020 •
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I have found another inconsistency, this time between volume fraction and isCovered(). I was able to fix this by performing a check on volfrac after every call to set_eb_data such that the covered status is consistent with whatever was just calculated. However, with further testing, it appears this approach leads to floating-point errors in EB2::coarsen_from_fine() so not such a good idea after all.

Edit: removed a bunch of code that didn't work.

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@darylbond @asalmgren