bendudson
`neutral_mixed` docs and spurious (?) mass factor
In the present docs https://hermes3.readthedocs.io/en/latest/equations.html#d-3d-neutral-mixed we have the following equations.
There are some errors here:
- missing factors of mass in the momentum equation breaking dimensional consistency,
- extra factors of mass multiplying $
\eta_n$ which seem to break dimensional consistency, - $
D = v_{th}^2 \nu$ instead of $D = v_{th}^2/\nu$ - Lack of parenthesis around viscous terms in pressure equation, so that the parallel viscous term has the wrong sign.
From my own notes (with u instead of v for velocity), the corrected equations could look as follows.
These equations can be seen symbolically in https://github.com/boutproject/hermes-3/blob/f841004fab190f5b652928f1e075ff64c8c0ade7/tests/mms/neutral_mixed_ddt_test.py#L29-L99. Note that the dimensionally inconsistent mass in or multiplying $\eta_n$ (etan) is actually present in the source.
Thank you so much for finding the errors in the docs @mrhardman! And the erroneous factor of mass as well - will correct it asap. Thankfully it's not as serious as it would appear - neutral viscosity should be off by "only" a factor of 2 for deuterium due to normalisation.
