about measure seepage discharge in triaxial test

Hello,

Please do not ask 4 separate questions in one thread. Please read our forum guidelines [1].

>but I found that these two values remained constant throughout the process (about - 1.02 and 1.02 in my simulation).It puzzles me.

Well ya, you are setting the permeability constant. Please review the command you are using for permeability [2].

>2. I also want to know what is the unit of the value measured by flow.getBoundaryFlux.(I checked the help document of Yade and couldn't find the relevant results)

Yade is generally unit-less. You decide the units based on your input parameters. Yade is just a calculator. Generally it is recommended to stick to SI input units so that your results are in SI units. i.e. this flux would be m^3/s in SI units.

>By the way,is this function(flow.getBoundaryFlux) used to measure permeability in flowengine.

I dont quite understand, that is the function used to measure fluid fluxes. You need fluid fluxes to compute permeability.

Cheers,

Robert

[1]https://www.yade-dem.org/wiki/Howtoask
[2]https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngine.permeabilityFactor

> the unit of the value measured by flow.getBoundaryFlux

It is in velocity * area.
B

Hello,
First of all, I would like to express my sincere apologies. What I'm worried about is that it will be complicated to divide into several questions.I will try to avoid this situation in my subsequent questions

>Well ya, you are setting the permeability constant. Please review the command you are using for permeability [2].

>>I checked [2] and seemed to understand something.The problem is that I set this value to negative, so the permeability is constant, right?(In other words, it should be positive to change the Seepage?)

>I dont quite understand, that is the function used to measure fluid fluxes. You need fluid fluxes to compute permeability.

I see,I will use this value to calculate permeability.

Thanks Robert and Bruno,I understand the problem of the unit.

Best wishes!

Hello,everyone.

I tried changing flow.permeabilityFactor to a positive value and other values.However,It seems that the data I record is always constant( flow.getBoundaryFlux(4) and (5) ).
In my understanding, with the increase of axial pressure in the process of triaxial compression, the permeability will change, which should not be a constant value.
How to deal with it?

Thanks.

> I tried changing flow.permeabilityFactor to a positive value and other values.However,It seems that the data I record is always constant

Please post a script showing what you say.
You "tried changing" or you "changed"?
It "seems" it is the same or it "is" the same?
Etc.

Bruno

Hello,I'm sorry I didn't make it clear,I will post my MWE in the end(The model is a cube generated by RandomDensePack,composed of 5000 particles with a side length of 0.05m )

Yes,I changed the value of flow.permeabilityFactor to 1,2,3,5,0.01,etc..
In fact, the point of my question is that the flow.getboundaryflux(4) and (5) recorded by plot.addData() has not changed in the whole process of triaxial compression failure (that is, it has always been a constant value). For example,When I set flow.permeabilityFactor to 5, the measured values(flow.getboundaryflux(4) and (5)) are always about - 73 and 73 throughout the triaxial compression process. However, as far as I know, the permeability should be a variable value in the process of triaxial compression failure

-----------------script----------------------
from yade import pack, ymport, plot, utils, export, timing
Wy=-10e6
Sy=-2e6
rate=-0.1
damp=0.4
stabilityThreshold=0.001
key='_triax_base_'
young=3000e9
name='JCFPM_triax'
compFricDegree=30
poisson=0.4

mn,mx=Vector3(0,0,0),Vector3(0.05,0.05,0.05)
O.materials.append(JCFpmMat(type=1,density=2640,young=young,poisson=poisson,tensileStrength=160e6,cohesion=1600e6,frictionAngle=radians(10),label='sphere'))
O.materials.append(JCFpmMat(type=1,frictionAngle=0,density=0,label='wall'))

walls=aabbWalls([mn,mx],thickness=0,material='wall')
wallIds=O.bodies.append(walls)
O.bodies.append(ymport.text('packing-JCFPM.spheres',scale=1,shift=Vector3(0,0,0),material='sphere',color=(0.6,0.5,0.15)))

triax=TriaxialStressController(
 maxMultiplier=1.+4e8/young,
 finalMaxMultiplier=1.+4e7/young,
 thickness = 0,
 stressMask = 7,
 internalCompaction=True,
)
newton=NewtonIntegrator(damping=damp)
O.timingEnabled=True

def recorder():
 yade.plot.addData(
 i=O.iter,
 e11=-triax.strain[0],#e22=-triax.strain[1],
 e33=-triax.strain[2],
 s11=-triax.stress(triax.wall_right_id)[0],#0+边界id为right
 s33=-triax.stress(triax.wall_front_id)[2],#2+边界id为front
 numberTc=interactionLaw.nbTensCracks,
 numberSc=interactionLaw.nbShearCracks,
 unb=unbalancedForce(),
 flux1=flow.getBoundaryFlux(4),
 flux2=flow.getBoundaryFlux(5)
)
 plot.saveDataTxt('triax_JCFPM_HM_Wy=10.0Mpa,Sy=2.0MPa')

def stop_condition():
 extremum=max(abs(s) for s in plot.data['s33'])
 s=abs(plot.data['s33'][-1])
 e=abs(plot.data['e33'][-1])
 if e < 0.001:
  return
 if abs(s)/abs(extremum) < 0.9 :
  print('Max stress and strain:',extremum,e)
  presentcohesive_count = 0
  for i in O.interactions:
          if hasattr(i.phys, 'isCohesive'):
               if i.phys.isCohesive == 1:
                   presentcohesive_count+=1
  print('the number of cohesive bond now is:',presentcohesive_count)
  O.pause()

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.5,label='is2aabb'),Bo1_Box_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=1.5,label='ss2sc'),Ig2_Box_Sphere_ScGeom()],
  [Ip2_JCFpmMat_JCFpmMat_JCFpmPhys()],
  [Law2_ScGeom_JCFpmPhys_JointedCohesiveFrictionalPM(recordCracks=True,Key='triax_JCFPM_HM',label='interactionLaw')]
 ),
 GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.7),
 triax,
 FlowEngine(dead=1,label='flow'),
 PyRunner(iterPeriod=int(1000),initRun=True,command='recorder()',label='data',dead=0),
 PyRunner(iterPeriod=1000,command='stop_condition()',dead=0),
 VTKRecorder(iterPeriod=500,initRun=True,fileName='triax/JFFPM-',recorders=['spheres','jcfpm','cracks'],Key='triax',label='vtk',dead=1),
 newton,
]

O.step()
ss2sc.interactionDetectionFactor=-1
is2aabb.aabbEnlargeFactor=-1
cohesiveCount = 0
for i in O.interactions:
 if hasattr(i.phys, 'isCohesive'):
              if i.phys.isCohesive == True:
                     cohesiveCount+=1
print('the origin total number of cohesive bond is:',cohesiveCount)
triax.goal1=triax.goal2=triax.goal3=Wy

while 1:
 O.run(1000,1)
 unb=unbalancedForce()
 print('unbalanced force:',unb,'mean stres:',triax.meanStress)
 if unb<stabilityThreshold and abs(Wy-triax.meanStress)/abs(Wy)<0.001:
  break

yade.timing.reset()
flow.dead=0
flow.debug=False
flow.fluidBulkModulus=2.2e9
flow.permeabilityFactor=5
flow.decoupleForces = False
flow.meshUpdateInterval=-1
flow.useSolver=4
flow.viscosity=0.001
flow.bndCondIsPressure=[0,0,0,0,1,1]
flow.bndCondValue=[0,0,0,0,0,Sy]

triax.internalCompaction=False
flow.emulateAction()
triax.stressMask=3
triax.goal1=Wy
triax.goal2=Wy
triax.goal3=rate

plot.plots={'e33':(('s33','g'),None,('unb','b')),'i':(('numberTc','b'),('numberSc','r'),None,('s33','y'))}
plot.plot(subPlots=False)
O.run()
-------------------------------------------------------

Sorry..Can anyone provide some ideas.. Thanks a lot!

Thanks Robert Caulk, that solved my question.