[PATCH] Fix up SAC calculations for ATM/bar confusion

[Chris Lewis]

. ]
>>
> I have noticed something which surely distords SAC-calculation when using
300 bar tanks. Subsurface is not taking into account the air unlinear
compressibility above 270 bar.
>
> Function bar_comp = -0.0007*bar*bar + 1.109*bar + 0.8
> would work from 250 to 300 bar very well (= close to wikipedia's table at
temp 27 C)
> where bar == pressure in bar  and  bar_comp == the pressure which will
give correct air surface volume when multiplied with tank volume and
divided with SURFACE_PRESSURE.
>
> Should the compressibility factor be counted in to_ATM (and not in
calculate_airuse or calculate_sac) ? To me the excessive calculation
between cuft, bar, L, atm, mbar seems confusing. Is it really necessary ?
If we put the factor to to_ATM shall we fix or break everything ?
>
> Jukka
> (I know it's easy for me to tell other how to do it and NOT SENDING ANY
PATCH..)

I suppose if accuracy in this calculation is important we should use a full
Van dear Waals method.  However this might be more hassle than its worth,
I'm afraid I'm no programmer so am completely unable to even try to help
:-(

Chris
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.hohndel.org/pipermail/subsurface/attachments/20130224/6b74cd16/attachment.html>