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[Soheil Safari <question701670@xxxxxxxxxxxxxxxxxxxxx>]

New question #701670 on Yade:
https://answers.launchpad.net/yade/+question/701670

Hello everyone;

Hope you are doing well.

I am using the PFV model for obtaining the permeability of saturated porous media during compaction.

I add a vertical load after the triaxial compaction for my purpose.

As you know, with decreasing the porosity the permeability should decrease. But I gained weird values for permeability.

# iter		   permeability		               porosity		
9000	  0.0040769404267505	        0.41192028080767573	
14000	  11.74354284652612	        0.4030884727731015	
19000	  13.343426253310719	        0.3923362673334938	
24000	  23.84251322618248	        0.37979613643988935	
29000	  7.022957721808432	        0.3660237961115663	
34000	  7.727306935671516	        0.352379674082547	
39000	  13.325689621243457	        0.3405623832436381	


I do not know what the reason is. Maybe it is because of the wrong wall number. After combining the models, there are more than 6 walls around the sample !!!

Would you please let me know which walls I should select for Qin = flow.getBoundaryFlux() to get proper permeability?

Here is my code:

###
from __future__ import print_function
from builtins import range
from yade import pack, plot
from yade import export

num_spheres=400# number of spheres
young=1e6
compFricDegree = 3 # initial contact friction during the confining phase
finalFricDegree = 30 # contact friction during the deviatoric loading
mn,mx=Vector3(0,0,0),Vector3(1,1,2) # corners of the initial packing

O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=radians(compFricDegree),density=2600,label='spheres'))
O.materials.append(FrictMat(young=young,poisson=0.5,frictionAngle=0,density=0,label='walls'))
walls=aabbWalls([mn,mx],thickness=0,material='walls')
wallIds=O.bodies.append(walls)

psdSizes,psdCumm=[.01,0.03,0.04,.05,.06,.08,.12],[0.,0.1,0.3,0.3,.3,.7,1.]
sp=pack.SpherePack()
sp.makeCloud(mn,mx,-1,0.3333,num_spheres,False, 0.95,seed=1) #"seed" make the "random" generation always the same
sp.toSimulation(material='spheres')

triax=TriaxialStressController(
	maxMultiplier=1.+2e4/young, # spheres growing factor (fast growth)
	finalMaxMultiplier=1.+2e3/young, # spheres growing factor (slow growth)
	thickness = 0,
	stressMask = 7,
	max_vel = 0.005,
	internalCompaction=False, # If true the confining pressure is generated by growing particles
)

newton=NewtonIntegrator(damping=0.2)

O.engines=[
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
		[Ip2_FrictMat_FrictMat_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()],label="iloop"
	),
	FlowEngine(dead=1, label="flow"),  #introduced as a dead engine for the moment, see 2nd section
	GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
	triax,
	newton
]

triax.goal1=triax.goal2=triax.goal3=-10000

while 1:
  O.run(1000, True)
  unb=unbalancedForce()
  if unb<0.001 and abs(-10000-triax.meanStress)/10000<0.001:
    break
    
setContactFriction(radians(finalFricDegree))


#B. Activate flow engine and set boundary conditions in order to get permeability
flow.dead = 0
flow.defTolerance = 0.3
flow.meshUpdateInterval = 200
flow.useSolver = 3
flow.permeabilityFactor = 1
flow.viscosity = 10
flow.bndCondIsPressure = [0, 0, 1, 1, 0, 0]
flow.bndCondValue = [0, 0, 1, 0, 0, 0]
flow.boundaryUseMaxMin = [0, 0, 0, 0, 0, 0]
O.dt = 0.1e-3
O.dynDt = False

def get_permeability():
    Qin = flow.getBoundaryFlux(2)
    Qout = flow.getBoundaryFlux(3)
    permeability = abs(Qin) / 1.e-4  #size is one, we compute K=V/∇H
    print("Qin=", Qin, " Qout=", Qout, " permeability=", permeability)
    return permeability

# walls
walls = aabbWalls()
top = walls[5]
O.bodies.append(walls)

# apply oedometric compression
top.state.vel = (0, 0, -0.06)

# porosity
O.engines += [PyRunner(iterPeriod=5000,command="plotAddData()",initRun=True)]  # runs  every 5000 iterations

def plotAddData():
    porosity = utils.porosity() 
    perm = get_permeability()
    plot.addData(iter=O.iter, time=O.time, porosity=porosity, perm=perm)
    plot.saveDataTxt("porosity.txt") #

# run
O.stopAtIter = 40100
O.run()
##

Many thanks in advance.

Best regards,
Soheil

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