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I: Re: Porosity
>thanks for your suggestions, I will try to put them in place.
>Some further considerations/corrections:
>For small range of final
>was meaning having a fixed PSD and a constant friction angle. I
was wrong in my
>previous message, the porosity changes if I change the
>Question: which value of friction angle do you use during
the compaction phase?
>Should be the final one or should be lower than that?
Would it be possible to
>run the analysis with a value equal to zero?
important point regarding
>the unbalanced force. I agree with you that the
value of unbalanced force
>should come down just cycling (the time step is not
zero) but that doesn't
>happen in the way I should expect. For instance in
your code, once you choose
>the expansion method, after each expansion you are
actually cycling without
>expanding for a certain number of iterations (look
at the bool
>isARadiusControlIteration), so I would expect that the unbalanced
>down during this process (of course before I have to get some
stresses at the
>walls) but it remains always around 1 until the stresses on
the walls become
>higher. I would expect that also at a small level of stress
on the walls, this
>value of unbalanced force remains quite low. I suppose
that the reason you (if
>it were you) put the bool isARadiusControlIteration
relays in the concept of
>maintaining a quasi-static equilibrium as much as
possible during the analysis.
>To make a summary I see that the unbalanced
force reaches low values (say 0.07
>or whatever) only after having compressed
the packing. Am I escaping something?
>>Ogg: Re: [Yade-
>>> I would need your help concerning the Triaxial. Since
>I need a
>>> specific value of final porosity, I am trying to do something in
>>> 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).
>problem. Just keep me updated so I know what happens in files.
>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
>it?), the computed
>>> unbalanced force is always very high and
>>There is nothing "bad" in keeping a constant radius until
unbF is small.
>the unbalanced force does not approach 0 with cycles
>nothing else than dynamic integration, there is
>>something wrong. The
>timestep is not 0?
>>The only problem I
see in your approach is you force the
>>want, which will result
in very big overlaps and high stress
>>likely. The porosity should be
the result of a "realistic" packing
>>> Could you give me
>>> suggestions or directions how to do
>that? I mean, how to fix the
value of final
>constant stress and decrease
friction a little bit at each step.
>will self-reorganize, and
porosity will decrease. Save the
>>packing state when
>porosity value cross
the value you want.
>>You can use this function to modify
>>void TriaxialCompressionEngine::setContactProperties(Scene * ncb,
>>frictionDegree)//I really mean "use", not copy ;)
>>All you have to do
>is a loop that will keep assigning frictionDegree
>>each n=~10 steps, with a
>decreased frictionDegree each time.
>>Note that big porosity variations
>occur with small values of
>>friction, in the range 0° < f < 5°.
>>> 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
>shapes) but to me it is always possible to say that
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
>>What is small range? I tried that
after your message and
>I got different
>>poro from different friction.
>>> Merci beaucoup.
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