Implement 2D neutral equation fixes originally part of AFN flux limiter branch #231
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Apply limiter/upwinding to both X and Y advection
Seems to work better for neutral perpendicular diffusion than MC.
Take field (Nn, Pn, NVn) and Dnn separately; only upwind the field, and use cell face average values for Dnn. Also add neutral_conduction switch.
target settings used in SOL and PFR regions, rather than SOL and PFR settings.
Seems to help with smoothness of profiles
Same as anomalous_diffusion, obtain flows in X and Y for output when diagnose = true. Note: Only saves perpendicular flux, not parallel flux.
- For debugging purposes
- added setting for pressure floor. Added temporary debug flags for using floored Nn and Pn in DnnNn and DnnPn calculation (otherwise they could unbalance and lead to density loss - need more testing). There is a secondary floor which kicks in at zero gradient, this is now linked to the primary floor (but 2 orders of magnitude below).
- Kappa and eta factors - Perpendicular advection and conduction factors - Add viscous heating Comes from the E AFN version on my fork
- Seems to make energy imbalance less imbalanced, but I haven't gone through the maths yet
This was referenced Oct 4, 2024
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There is an outstanding PR which has fixes for neutral equations as well as the new limiter scheme. It lives on my fork at mikekryjak#5.
The flux limiter scheme has caused us lots of inexplicable slowdowns, and we were waiting with the merge until we resolved that along with the X-point temperature spike bug. With those two problems having turned out to be challenging, I think we should fix the equations in a separate PR as they are simply not correct. We can then tackle the limiter scheme methodically bit by bit.
I had to merge the other 2D neutral fixes PR into this as both are required for the tests. That other PR is causing checkerboarding in the neutral_mixed integrated test.
To do:
Original work from @bendudson:
Impact on results is not insubstantial, especially at the target. Performance is the same or slightly faster - probably dependent on the change in conditions rather than being more difficult numerically.
OMP
Target
Poloidal slice
