How to set the PeriodicFlowEngine

Asked by Zhicheng Gao on 2021-05-22

I build the scene in the periodic boundary, so there are no walls. Does that mean I should use flow.boundaryUseMaxMin= [1,1,1,1,1,1], given that the label of PeriodicFlowEngine is set to flow.
Another question, I have read [1], the total force generated on one particle by the fluid includes the effects of absolute pressure and viscous stress. Thus, should I set flow.pressureForce=True, flow.viscousShear=True, flow.viscousNormalBodyStress=True, flow.viscousShearBodyStress=True, flow.normalLubrication=True, flow.shearLubrication=True?

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Bruno Chareyre
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Zhicheng Gao (zhichenggao) said :
#1
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Bruno Chareyre (bruno-chareyre) said :
#2

Hi,

1/ No, if it is periodic there is just no walls. You simply impose a macroscopic pressure gradient. (well... it really depends what you are trying to achieve, not clear from the question).

2/ As for "should I set", it really depends on what you are trying to simulate, so I cannot answer.

Bruno

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Zhicheng Gao (zhichenggao) said :
#3

Dear Bruno,
Thank you for your response. In my mind, the flow problem is a boundary value problem, so the PeriodicFlowEngine should get the position and value of the boundary. I have read the documentation on PeriodicFlowEngine, I don’t know if my understanding is wrong. In my opinion, boundaryUseMaxMin is used to set the boundary position. The default Boolean vector of boundaryUseMaxMin is true on six faces, which means using the max-min coordinates of X, Y, and Z to add spheres as the boundary. Otherwise, the wall position is used. I saw the related problem in Answer #3 in https://answers.launchpad.net/yade/+question/688195.

another question, I have read your paper 'Pore-Scale Modeling of Viscous Flow and Induced Forces in Dense Sphere Packings', in that paper, the total force generated on one particle by the fluid includes the effects of absolute pressure and viscous stress. So I set flow.pressureForce=True, flow.viscousShear=True, flow.viscousNormalBodyStress=True, flow.viscousShearBodyStress=True, flow.normalLubrication=True, flow.shearLubrication=True. Is that correct? The complete code looks like this:

from yade import pack,qt,utils,ymport
from yade import export
from yade import timing
from yade import plot
from builtins import range
import numpy
import time
from math import *

O.load('prova.xml')

num_spheres=5000
young=750.e6
finalFricDegree = 0.35
graindensity=2600.0
poisson=0.17
en=0.9
sigmaIso=-150.e3
radiusR=0.001/2.
D50=radiusR*2.0

#O.materials.append(FrictViscoMat(young=young,poisson=poisson,frictionAngle=compFricDegree,density=graindensity,betan=0.0336,label='spheres'))

triax=PeriTriaxController(
 dynCell=True,
 mass=0.2,
 goal=[sigmaIso,sigmaIso,sigmaIso],
 stressMask=7,
 maxStrainRate=[0.0001,0.0001,0.0001],
 label='triax')

newton=NewtonIntegrator(damping=0.1)

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb()]),
 InteractionLoop(
         [Ig2_Sphere_Sphere_ScGeom()],
         [Ip2_FrictViscoMat_FrictViscoMat_FrictViscoPhys()],
         [Law2_ScGeom_FrictViscoPhys_CundallStrackVisco(traceEnergy=True)]
 ),
 PeriodicFlowEngine(dead=1,label="flow"),
 GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.5),
 triax,
 newton
]

while 1:
 O.run(1000, True)
 unb=unbalancedForce()
 if unb<0.00001:
  break

triax.dead=0
flow.dead=0

flow.pressureForce=True
flow.viscousShear=True
flow.viscousNormalBodyStress=True
flow.viscousShearBodyStress=True
flow.normalLubrication=True
flow.shearLubrication=True

flow.defTolerance=0.1
flow.meshUpdateInterval=200
flow.useSolver=3
flow.permeabilityFactor=1
flow.viscosity=0.001
flow.bndCondIsPressure=[0,0,0,0,1,1]
flow.bndCondValue=[0,0,0,0,0,0]
GlobalStiffnessTimeStepper.dead=True
O.dt=min(0.5*PWaveTimeStep(),0.5*1./1200.*pi/flow.viscosity*graindensity*(D50/2.)**2)
O.dynDt=False

O.run(10,1)

while 1:
 O.run(5000, True)
 unb=unbalancedForce()
 if unb<0.0001:
  if O.cell.velGrad[0,1]<0.01:
   O.cell.velGrad=O.cell.velGrad+Matrix3(0,0.001,0, 0,0,0, 0,0,0)
   O.dt=min(0.5*PWaveTimeStep(),0.5*1./1200.*pi/flow.viscosity*graindensity*(D50/2.)**2)
  if O.cell.velGrad[0,1]>0.01:
   break

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Best Bruno Chareyre (bruno-chareyre) said :
#4

As the name suggests, PeriodicFlowEngine is for periodic (no-)boundary condition. So no it is not really a "boundary" value problem. It is a periodic field problem.

flow.pressureForce=True will compute the drag forces (from both pressure and viscous stress) resulting from macroscopic sliding velocity between the two phases.

The other flags are related to lubrication forces: short range pair interactions playing against the relative movement of particles. These forces were added on the top of the drag forces _after_ Catalano 2011.
See [2,3]

[2] https://link.springer.com/content/pdf/10.1007/s10035-015-0560-6.pdf
[3] https://www.sciencedirect.com/science/article/pii/S0032591020305064

Bruno

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Zhicheng Gao (zhichenggao) said :
#5

Thanks Bruno Chareyre, that solved my question.