WIP: Neutral model improvements #165
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Trying to get model closer to Horsten thesis (2019). The net effect of these changes is to: - Increase heat conduction by 5/3 - Increase heat advection by 5/3 - Increase viscosity by 5/2 - Add viscous heating The atomic rates used in diffusion, viscosity, and heat conduction coefficients are still different from Horsten 2019.
Convert from viscous heating power to rate of change of pressure.
Intended to be similar to Wim Van Uytven et al "Assessment of advanced fluid neutral models for the neutral atoms in the plasma edge and application in ITER geometry" Nucl. Fusion 62 (2022) 086023 Significantly slows convergence; may be something wrong in implementation.
Previous commit accidentally reversed the sign of the cross-field particle flow, resulting in very poor convergence. Flux limits are now enabled by default.
- This is for testing and the Rnn term may be removed permanently later - The AFN limiters don't have this.
- For testing
Check if float option is < 0 rather than equal to -1. Remove some unused and commented-out code.
Flux limited particle flux is used in momentum flux before the momentum flux is limited. Particle flux limiter applied to advection of momentum and pressure.
Applies a time-averaging to the flux limit factors, with a given timescale. Doesn't appear to have much benefit in quick tests, but left in and turned off by default. May be removed if it really doesn't do anything useful.
The linear flag is set when the time integrator is in a linear solve. Components can disable nonlinear updates to (sometimes) improve convergence.
- Add a relaxation timescale to the coefficients. Damps oscillations and improves convergence. - Calculate fluxes at cell edges, and use maximum local flux to calculate flux limit factors - Near boundaries use the minimum of the flux limit factor in the last two cells. This is because fluxes in the last cell may not be calculated correctly in the flux limit calculation. - Don't update coefficients in a linear solve (this seems to be a small effect)
- Disable maximum_mfp by default - Use a timescale of 1e-6 for the flux limit factor relaxation (`flux_factor_timescale` option).
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Development has been split off into other PRs. Limiter development: mikekryjak#6 |
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Trying to get model closer to Horsten thesis (2019).
The net effect of the changes so far is to:
The atomic rates used in diffusion, viscosity, and heat conduction coefficients are still different from Horsten 2019.