# yade-users team mailing list archive

## Porosity

```Hi Bruno,

I would need your help concerning the Triaxial. Since I need a
specific value of final porosity, I am trying to do something in your code but
without success (BTW, I DON'T want to modify your code, if it will work I will
manage to add a flag or something like that).
Let's I am using the expansion
method, I have tried to do what it has been done in terms of stresses to get
the final packing in terms of porosity as:

else //if internal compaction
{

if (porosity>0.60)
previousMultiplier = maxMultiplier;
else{

previousMultiplier = 1. + fabs(n_fin - porosity)
/n_fin*(maxMultiplier-1.);
}
if
(porosity<=n_fin) {
Unb = ComputeUnbalancedForce(ncb);
(1)				if (Unb >
0.1) previousMultiplier = 1.0;}

previousStress = meanStress;

controlInternalStress(ncb, previousMultiplier);
}
}

so basically in the line
(1) it is like saying "cycle" without expanding if the value of Unb force is
too high. Unfortunately "cycling" doesn't help (why? Should it?), the computed
unbalanced force is always very high and around 1.
Could you give me any
suggestions or directions how to do that? I mean, how to fix the value of final
porosity..
Actually I remember you suggested me to play with the friction angle
but I don't remember exactly..
I have got that having a specific PSD and a
friction angle we can get only one possible value of final porosity (or a very
small range of it) and that's true with the DEM (cause we are dealing with
spheres and not irregular shapes) but to me it is always possible to say that
for the same PSD I would like to run the Triaxial with an higher porosity
(higher than that maximum dense packing I get with this method either with
compaction or expansion).

Merci beaucoup.

Chiara

guess around the visualization of the force network, I remember Vaclav answered
something like:

type in Dem3DofGeom_SphereSphere,cpp
bool
Gl1_Dem3DofGeom_SphereSphere::normal=true

then in the mask the combination of
Interaction_Geometry and intrAllWire should give the network (not sure, I have
to try it again)

```