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[Bruno Chareyre <1734653@xxxxxxxxxxxxxxxxxx>]

** Description changed:

  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 may be mainly due to a crack an its opening.
- Typically V=V(tetrahedron)-opening*area-matrixPorosity.
+ 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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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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