Christian, We better move this discussion back to yade-dev.
> >> The fluid force Ff[i] = p*A[i] is already included if you read >> O.forces.f[wallId]. As soon as PFV comes before TriaxController, you >> don't have to compute it again. > > You mean PFV must be defined before TSC in O.engines to get wall-fluid > interaction automatically? Or do you mean the force is already > calculated, but it does not act on the wall? If PFV is before TSC in engines it is automatic, yes. > >> The problem is in the definition of kn, not in the definition of dF. >> Currently kn is the stiffness of the solid phase. It should be the >> cumulated stiffness of both phases. > > What is the cumulated stiffness of both phases? kn + k_fluid? The stiffness should reflect the stress-strain relation in uniaxial undrained deformation. Should be Young+k_fluid/porosity I think, but it is not required to be absolutely exact (e.g. assuming porosity=0.3 is good enough). > >> If the fluid is incompressible the cumulated stiffness becomes infinite, >> which is consistent since an undrained test with incompressible fluid is >> a ill-posed problem. >> You could test this idea by using a user defined stiffness in order to >> see if you can stabilise the engine by defining a higher stiffness. >> If so, TSC could automatically search a PFV engine in O.engines, and if >> found it would use pfv.bulkModulus to update the stiffness. > > Fine, but I still have a problem in understanding what a fluid > stiffness is. How can I update the stiffness from bulk modulus? Is it > kn += K/A? Then what is A? Fluid stiffness is the inverse of fluid compressibility. ;) PFV.bulkModulus is the stiffness. Maybe not very well named, since bulk is more commonly used for solids or mixtures. Cheers Bruno _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
