[PATCH] Re: New Bug Reports/Feature Requests

[Linus Torvalds]

On Wed, Mar 2, 2016 at 9:25 AM, Dirk Hohndel <dirk at hohndel.org> wrote:
>
> So since Robert's formula /should/ be the right way to calculate the
> compensation factors, let's figure out what about it is broken and use
> "matches the wikipedia data" as a measuring stick for that.

Well, the thing is, Robert's formula isn't actually physical, it's
fundamentally an approximation too.

In fact, it's arguably much less physical than the van der Waals
equation, that at least tries to model the physical behavior, while
afaik the Redlich–Kwong equation is _purely_ an empirical
approximation.

The first paragraph in the wikipedia page really does sum it up:

  https://en.wikipedia.org/wiki/Redlich%E2%80%93Kwong_equation_of_state

so to some degree, Lubomirs least-square polynomial would actually be
superior: it is the same kind of approximation, but it's an
approximation that has been specialized for one particular gas and
pressure/temperature range we happen to care about.

The Redlich–Kwong equation is intended to be much more general, but
exactly because of that it's much less accurate at least for one case
we care about.

Side note: according to Wikipedia there are various newer refined
versions with more complexity (and some with more per-gas constants).
So it's possible that we could still get it all - both the "multiple
gases" _and_ "sufficient accuracy".

                        Linus