Re: Material Sand for well logging problems

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Mon, 25 Jun 2012 12:21:05 -0700 (PDT)

Dear Carolin,

to define a mixture of sand (actually quartz) and air you need first to
define a compound Sand. I suggest a quartz density 2.32:
MATERIAL 0.0 0.0 2.32 0.0 0.0 0.0 Sand
COMPOUND 1.0 SILICON 2.0 OXYGEN 0.0 0.0 Sand
(note that the relative fraction is given in number of atoms in a molecule)
and a compound for air:
MATERIAL 0.0 0.0 0.0012048 0.0 0.0 0.0 AIR
COMPOUND -1.24E-4 CARBON -0.755267 NITROGEN -0.231781 OXYGEN AIR
COMPOUND -0.012827 ARGON 0.0 0.0 0.0 0.0 AIR
(relative fractions in volume)
and then a compound of sand and air:
MATERIAL 0.0 0.0 1.6 0.0 0.0 0.0 AIRSand
COMPOUND -0.6 Sand -0.4 AIR 0.0 0.0 AIRSand
(relative fractions in volume)

The above gives you a homogeneous mixture of the right average density, but not
with the right porosity.
You can use instead just a material Sand as described above, with a density
equal to the local density of a sand grain:
MATERIAL 0.0 0.0 2.32 0.0 0.0 0.0 Sand
COMPOUND 1.0 SILICON 2.0 OXYGEN 0.0 0.0 Sand
and then command MAT-PROP to define a factor RHOR indicating the ratio between
the average and the local density:
MAT-PROP 0.0 0.69 0.0 Sand 0.0 0.0
You can look up command MAT-PROP in the manual, especially Example 2.
This will give you a material with the right density for tracking
(2.32*0.69 = 1.6 g/cm3) but with a higher local density (2.32) for the
particle interactions. But there is no air, just a difference in density.
I don't know which of the two solutions you will prefer. I would prefer the
second one, because I think interactions with air are negligible.


On Fri, 22 Jun 2012, Carolin Pezenka wrote:

> Dear FLUKA and FLAIR experts,
> I want to model the behavior of low energy neutrons in a matrix of
> Sand with different porosity for calibration of a neutron logging
> tool. In previous discussions I couldn't find any help for this. My
> idea was to define the material similar to concrete. The following
> cards are suggested for pure quartzsand (SiO2) with air filled
> porespace of 40 %:
> MATERIAL 1.6 Sand
> I am not sure, that I really understood the background, how Fluka
> build the material from this input. Is this really a good
> approximation for sand? I mean, does the structure and spatial
> distribution of the SiO2 and the air doesn't care? Which type of
> fraction (atom/mass/volume) is to use? Are there other or better
> possibilities to get a sand matrix?
> Furthermore, is there anybody dealing with geophysical well logging
> problems to get in contact and discussion with?
> Best regards
> Carolin
Received on Tue Jun 26 2012 - 12:44:10 CEST

This archive was generated by hypermail 2.2.0 : Tue Jun 26 2012 - 12:44:10 CEST