You are right, we probably mixed up a few things... Sorry for that. If the main question concerns the reference volume Vo, here is my understanding of your proposals:
1 - Vo=matrixPorosity*cellVolume for a cell in the intact matrix 2 - Vo=aperture*area+matrixPorosity*cellVolume for a cell cut by a pre-existing fracture (DFN). In the latter case, jointInitialAperture and slotInitialAperture (or, more generally, residual aperture) are the right candidates for aperture (as suggested in your first message). There should not be any problem with aperture being equal to zero because of the +matrixPorosity*cellVolume. Q1 - How do we deal with multiple prefractured edges? DFNs usually correspond to individual fracture planes which would respectively cross 1 or 2 edges of the facet. Also, several fracture planes can eventually cross the same facet with different orientations. If we forget the multiple planes configuration for the moment, aperture should be equal to 1*residualAperture even if 2 edges are concerned (no additivity), right? If you agree on this, then, we need to think about the area -> Q2. Q2 - What about the area? Right now, conductivity is computed assuming squared parallel plates with reference length equal to the distance between the connected cells centers. Related to Q1, area should be "weighted" by the number of fractured edges, right? Using triangular surfaces joining the middle of the edge and the cell centers would probably be ideal with respect to the geometry of our problem but then the cubic law used for computing the conductivity would be kind of flawed, right? What about associating rectangular plates of dimensions 0.5*cell1CenterToCell2Center*middleOfBrokenEdge1ToMiddleOfBrokenEdge2 to each edges? The conductivity would then be adapted correspondingly to the number of fractured edges. Q3 - Should we consider cellVolume as V(tetrahedron) or as V(tetrahedron)-V(spheres)? I guess it depends on how we compute dV=V-Vo. If V=V(tetrahedron) then cellVolume=V(tetrahedron), right? Q4 - How do we define matrixPorosity? Any chance that we could relate matrixPorosity to the permeabilityFactor used to scale down the overall permeability or do we simply relate to the porosity of the material? This is probably stupid to relate permeability to porosity but I am asking because it is sometimes difficult to have the data. Q5 - If statement 2 is confirmed, do we need to take into account the induced cracks contribution to V in the calculation of dV=V-Vo? Luc -- You received this bug notification because you are a member of Yade developers, which is subscribed to Yade. 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 To manage notifications about this bug go to: https://bugs.launchpad.net/yade/+bug/1734653/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : yade-dev@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
