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[Bruno Chareyre <1362090@xxxxxxxxxxxxxxxxxx>]

Didn't try the script yet, but one problem is that the boundaries of
your system are defined using min/max coordinates of the spheres, it
does not reflect the movement of the walls at all. Thus the total volume
change is wrong.

You need to assign the walls as boundary conditions, just like in the oedometer example:
flow.boundaryUseMaxMin=[0,0,0,0,0,0]

And if the numbering of the walls is not the same as in triaxial scripts (0 to 5), you need to list them explicitely:
flow.wallIds=[x-,x+,y-,y+,z-,z+]

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https://bugs.launchpad.net/bugs/1362090

Title:
  problem with pressure calculation in PFV cells

Status in Yet Another Dynamic Engine:
  New

Bug description:
  Hi,

  I want to get the pore pressure of a saturated soil sample in an
  undrained triaxial test when the sample volume is decreasing.

  ...
  TriaxialStressController(thickness=0,stressMask=7,internalCompaction=False,label='triax')
  ...

  	triax.goal1 = 35000
  	triax.goal2 = 35000
  	triax.goal3 = 70000
  	triax.wall_back_activated = False
  ...
  	flow.viscosity = 1.3e-3
  	flow.fluidBulkModulus = 2e9
  	flow.bndCondValue=[0,0,0,0,0,0]
  	flow.bndCondIsPressure=[0,0,0,0,0,0]
  ...

  For one of my simulations a decrease of ca. 1,8 % in porosity (=-dV/V)
  is obtained. When I calculate corresponding pressure increase I get

  dp = K*(-dV/V) = 2e9*0.018 = 36000000 Pa

  But the output from PFV shows maximum average pressures around of 16
  Pa (not MPa!). As long as I use SI units the output of
  flow.averagePressure() should be Pa, right?

  So is there a problem in the code or did I miss something in the
  compressibility option of PFV?

  regards,

  christian

  
  ###additional info:

  I double-checked my script and did not see anything wrong. So I think
  it is on C++ side. So I was going on testing PFV method:

  I also tested a drained situation with incompressible fluid. The porosity is decreasing due to a triggered collapse of the grain structure, but the pore pressure gets negative (see attachment).
  So I think it is a bug in pressure calculation of PFV method.

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