'flux registers' for edge-centered EMFs?

[WeiqunZhang]

Discussed in #2511

^{Originally posted by BenWibking December 2, 2021}
Hi,

We are planning to implement face-centered MHD in Quokka. Is there a 'flux register' to do the correction at coarse-fine interfaces of edge-centered EMFs in AMReX? In Chombo, this can be accomplished with LevelFluxRegisterEdge, which has a similar API to YAFluxRegister.

Example:

There are a number of corner cases (see panels a-d copied below). (In Athena++, this step is also done at all shared edges between grids on the same resolution level in order to avoid roundoff errors, but it's not currently clear whether this will be necessary.)

[BenWibking]

Is this something that is likely to be available on a ~few months timescale? The reason I ask is because Mark (@markkrumholz) and I are advising a PhD student on implementing method-of-lines MHD in Quokka and whether this will be available in AMReX would significantly affect the direction we go.

I see that there is now a CTU+MHD implementation in Castro. This could be useful for Castro if subcycling AMR is desired for that. In principle, FLASH could also use this, although they might instead average down the edges before doing the update.

[WeiqunZhang]

We will give this a push in the next few weeks.

[BenWibking]

Ok, thanks for the update!

[BenWibking]

@WeiqunZhang Just wanted to follow up on this.

[WeiqunZhang]

@BenWibking Thanks for reminder!