Ffrom: V. Antonuccio-Delogu, INAF-Catania Astrophysical Observatory, ITALY
Code: FLASH
Version: 2.3
Description: I believe that the scalings of the "ideal gas constant" and
Boltzmann" constant in the calls of add_constant_to_db at lines 196 and 199
are wrong. Both constants have dimensions: [energy] [temp]^-1 [mole]^-1 =
[length]^2 [time]^-2 [temp]^-1. Then, the dependence on mass should be
dropped, which means that lines 195-197 should read:
call add_constant_to_db ("Boltzmann", 1.38065812E-16, &
& 2., -2., 0., &
& -1., 0.)
rather than:
call add_constant_to_db ("Boltzmann", 1.38065812E-16, &
& 2., -2., 1., &
& -1., 0.)
and analogously for the ideal gas constant.
Note that in eos.F90, eos1d.F90 they are used to deduce the pressure:
pres = gascon * dens * temp * abarinv
If density has dimensions: [mass] [length]^-3, then, in order that pressure
has the right dimensions ([mass] [length]^-1 [time]^-2) it is necessary that
the dimension of gascon be: [length]^2 [time]^-2 [temp]^-1.
I enclose a version of physical_constants.F90 which includes this correction.
In this new version I also define new units, which I denote as "FLY" (see
lines 169-171), defined in such a way that: length_unit = 1 Mpc, time_unit =
2/(3H_0), mass_unit=5.23e12 M_sol, H_0 = 100 km/sec/Mpc. In these units, the
gas constants has a value: gascon = 3.69 * 10^-7. Using the uncorrected
scaling in the original physical_constants.F90 one gets a value of ~ 10^-59
for gascon in FLY units. After the proposed correction, one recovers the
correct values.
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Vincenzo ANTONUCCIO-DELOGU *
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VISITING COPENHAGEN ASTROPHYSICAL OBSERVATORY *
July 1st - September 8th, 2004 *
Tlf.: +45 - 35 32 59 05 *
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INAF - Catania Astrophysical Observatory *
ITALY *
Citta' Universitaria *
Via Santa Sofia 78 *
I-95125 Catania - ITALY *
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Fax: + 39-095-33 05 92 *
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e-mails: van@ct.astro.it, antonucc@tac.dk *
WWW: http://w3.ct.astro.it/CHEAL/cheal.html *
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