yade-dev team mailing list archive

[Luc Scholtès <lscholtes63@xxxxxxxxx>]

I believe we are somehow converging.

Just a couple of additional remarks.

1 - Regarding the area associated to the broken edges:

If you look at the attached drawing, you'll see that we have actually 2 cases:
1) the 2 broken edges are associated to 2 individual cracks
2) the 2 broken edges are associated to the same fracture plane
In 1), I agree with you and the triangular surfaces are not coplanar
In 2), the triangular surfaces should be coplanar to account for the fact the the broken edges belong to the same fracture plane.
If we are concerned with the calculation of Vo, case 2) should prevail since we are dealing with pre-existing fracture planes rather than individual cracks but it would probably be easier (and more consistent?) to use the same logic for fracture planes and cracks so we should probably go for case 1). What do you guys think about that?

2 - Regarding the cubic law for computing the conductivity:

The cubic law is based on the concept of rectangular parallel plates of
length L and width W (cf. drawing) and I don't know how we could adapt
it to the case of triangular plates. Considering rectangular plates
instead of triangular ones seems like something reasonable in our case.
If you agree on this assumption, then we need to decide how to compute
W. As a first guess, I would go for W equal to the distance between the
middle of the broken edge (location of the crack) and the barycentre of
the facet. What do you guys think about that?

Luc


** Attachment added: "facetCrackLogic.jpg"
   https://bugs.launchpad.net/yade/+bug/1734653/+attachment/5020309/+files/facetCrackLogic.jpg

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https://bugs.launchpad.net/bugs/1734653

Title:
  DFN+fluid compressibility not using the correct reference volume

Status in Yade:
  New

Bug description:
  In the basic PFV scheme the incremental change of density of a pore
  fluid after a change of pore volume is dependent on dV/Vo where Vo is
  the reference pore space within a tetrahedral cell [1], i.e.
  V(tetrahedron)-V(spheres).

  In DFNFlow "V" should reflect the fact that porosity is mainly due to cracks, i.e. it is much smaller than the numerical porosity calculated between spheres.
  Typically V=opening*area+matrixPorosity*cellVolume
  Currently it is using the same formula, hence overestimating the compressibility effect (because the DEM porosity is larger than a typical rock porosity). What should be the reference "opening" in above formula is to be clarified though, it has physical as well as numerical implications. Maybe slotInitialAperture is a candidate? Let you DFN people tell what it should be.

  Note that the "dV" is less a problem because it is a difference
  (independent on the choice of the reference volume), so the
  incompressible scheme is not affected.

  Bruno

  [1]
  https://github.com/yade/trunk/blob/master/pkg/pfv/FlowEngine.ipp.in#L439

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