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Message #29370
[Question #706573]: Troble with porosity calculation
New question #706573 on Yade:
https://answers.launchpad.net/yade/+question/706573
Hello,
I was able to create a sphere packing with gravity deposition and oedometric test. So, I create a calculation to calculate the porosity, but the result that I get is negative which doesn't make sense. The result is around 25.00%
The following is my code:
import random
import math
from yade import geom, pack, utils, plot, ymport
import pandas as pd
# Define material properties
youngModulus = 1e7
poissonRatio = 0.25
density = 2000
# Create material
material = O.materials.append(FrictMat(young=youngModulus, poisson=poissonRatio, density=density))
# Define cylinder with funnel parameters
center = (0, 0, 0)
diameter = 0.102
height = 0.18
# create cylindrical body with radius 0.102 m and height 0.064 m
cylinder = geom.facetCylinder(center=center, radius=diameter/2, height=height, segmentsNumber=200, wallMask=6)
# assign material to each body in the cylinder
for body in cylinder:
body.bodyMat = material
# add cylinder to simulation
O.bodies.append(cylinder)
# Define cylinder with funnel parameters
center1 = (0,0,height/2)
dBunker = 0.4
dOutput = 0.102
hBunker = 0
hOutput = 0.15
hPipe = 0
# create funnel as a bunker with diameter 0.102 m, height 0.064 m
funnel = geom.facetBunker(center=center1, dBunker=dBunker, dOutput=dOutput, hBunker=hBunker,hOutput=hOutput, hPipe=hPipe, segmentsNumber=200, wallMask=4)
# assign material to each body in the funnel
for body in funnel:
body.bodyMat = material
# add funnel to simulation
O.bodies.append(funnel)
# define sphere parameters and number of spheres
rMean1 = (0.0125+0.019)/4
rRelFuzz1 = ((0.019-0.0125)/4)/rMean1
num1 = 17
rMean2 = (0.0095+0.0125)/4
rRelFuzz2 = ((0.0125-0.0095)/4)/rMean2
num2 = 53
rMean3 = (0.00475+0.0095)/4
rRelFuzz3 = ((0.0095-0.00475)/4)/rMean3
num3 = 1267
rMean4 = (0.00236+0.00475)/4
rRelFuzz4 = ((0.00475-0.00236)/4)/rMean4
num4 = 11624
#create empty sphere packing
sp = pack.SpherePack()
# generate randomly sphere
sp.makeCloud((-dBunker/4,-dBunker/4,1.3*height),(dBunker/4,dBunker/4,2*height), rMean = rMean1, rRelFuzz = rRelFuzz1, num = num1)
sp.makeCloud((-dBunker/4,-dBunker/4,1.3*height),(dBunker/4,dBunker/4,2*height), rMean = rMean2, rRelFuzz = rRelFuzz2, num = num2)
sp.makeCloud((-dBunker/4,-dBunker/4,1.3*height),(dBunker/4,dBunker/4,2*height), rMean = rMean3, rRelFuzz = rRelFuzz3, num = num3)
sp.makeCloud((-dBunker/4,-dBunker/4,1.3*height),(dBunker/4,dBunker/4,2*height), rMean = rMean4, rRelFuzz = rRelFuzz4, num = num4)
# add the sphere pack to the simulation
sp.toSimulation(material = material)
for body in O.bodies:
if not isinstance(body.shape, Sphere):
continue
if body.shape.radius >= rMean1 :
body.shape.color = (0,0,1) #blue
if body.shape.radius <= rMean1 and body.shape.radius > rMean2:
body.shape.color = (0,0,1) #blue
if body.shape.radius <= rMean2 and body.shape.radius > rMean3:
body.shape.color = (1,0,0) #red
if body.shape.radius <= rMean3 and body.shape.radius > rMean4:
body.shape.color = (0,1,0) #green
if body.shape.radius <= rMean4 :
body.shape.color = (1,1,0) #yellow
O.engines = [
ForceResetter(),
# sphere, facet, wall
InsertionSortCollider([Bo1_Sphere_Aabb(), Bo1_Facet_Aabb(), Bo1_Wall_Aabb()]),
InteractionLoop(
# the loading plate is a wall, we need to handle sphere+sphere, sphere+facet, sphere+wall
[Ig2_Sphere_Sphere_ScGeom(), Ig2_Facet_Sphere_ScGeom(), Ig2_Wall_Sphere_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]
),
NewtonIntegrator(gravity=(0, 0, -1000), damping=0.3),
# the label creates an automatic variable referring to this engine
# we use it below to change its attributes from the functions called
PyRunner(command='checkUnbalanced()', realPeriod=2, label='checker'),
]
O.dt = PWaveTimeStep()
for body in O.bodies:
if not isinstance(body.shape, Sphere):
continue
if body.shape.radius == 0.0125/2: #SP
body.shape.color = (0,0,1) #blue
if body.shape.radius == 0.0095/2: #SP1
body.shape.color = (1,0,0) #red
if body.shape.radius == 0.00475/2: #SP2
body.shape.color = (0,1,0) #green
if body.shape.radius == 0.00236/2: #SP3
body.shape.color = (1,1,1) #white
# the following checkUnbalanced, unloadPlate and stopUnloading functions are all called by the 'checker'
# (the last engine) one after another; this sequence defines progression of different stages of the
# simulation, as each of the functions, when the condition is satisfied, updates 'checker' to call
# the next function when it is run from within the simulation next time
# check whether the gravity deposition has already finished
# if so, add wall on the top of the packing and start the oedometric test
def checkUnbalanced():
# at the very start, unbalanced force can be low as there is only few contacts, but it does not mean the packing is stable
if O.iter < 15000:
return
# add plate at the position on the top of the packing
# the maximum finds the z-coordinate of the top of the topmost particle
O.bodies.append(wall(max([b.state.pos[2] + b.shape.radius for b in O.bodies if isinstance(b.shape, Sphere)]), axis=2, sense=-1))
global plate # without this line, the plate variable would only exist inside this function
plate = O.bodies[-1] # the last particles is the plate
# Wall objects are "fixed" by default, i.e. not subject to forces
# prescribing a velocity will therefore make it move at constant velocity (downwards)
plate.state.vel = (0, 0, -.8)
# start plotting the data now, it was not interesting before
O.engines = O.engines + [PyRunner(command='addPlotData()', iterPeriod=200)]
# next time, do not call this function anymore, but the next one (unloadPlate) instead
checker.command = 'unloadPlate()'
def unloadPlate():
# if the force on plate exceeds maximum load, start unloading
if abs(O.forces.f(plate.id)[2]) > 1e4:
plate.state.vel *= -1
# next time, do not call this function anymore, but the next one (stopUnloading) instead
checker.command = 'stopUnloading()'
def stopUnloading():
if abs(O.forces.f(plate.id)[2]) < 1e3:
# calculate the volume of the packing
volume_packing = 0
num_spheres = 0
for b in O.bodies:
if isinstance(b.shape, yade.wrapper.Sphere):
volume_packing += 4/3 * math.pi * b.shape.radius**3
num_spheres += 1
# print the number of spheres and volume of packking
print("Number of spheres:", "{:d}".format(num_spheres))
print("V Packing:", "{:e}".format(volume_packing))
# print the height of the plate
top = abs(plate.state.pos[2] - height/2)
print("Plate height:", top)
# calculate the volume of the cylinder
new_volume_cylinder = math.pi * (0.051)**2 * top
# calculate the porosity and porosity percentage
new_porosity = (new_volume_cylinder - volume_packing) / new_volume_cylinder
new_porosity_percent = new_porosity * 100
print("V Cylinder:", "{:e}".format(new_volume_cylinder))
print("Porosity:", "{:.2f}".format(new_porosity))
print("Porosity:", "{:.2f}%".format(new_porosity_percent))
# O.tags can be used to retrieve unique identifiers of the simulation
# if running in batch, subsequent simulation would overwrite each other's output files otherwise
# d (or description) is simulation description (composed of parameter values)
# while the id is composed of time and process number
plot.saveDataTxt(O.tags['d.id'] + '.txt')
O.pause()
def addPlotData():
if not isinstance(O.bodies[-1].shape, Wall):
plot.addData()
return
Fz = O.forces.f(plate.id)[2]
plot.addData(Fz=Fz, w=plate.state.pos[2] - plate.state.refPos[2], unbalanced=unbalancedForce(), i=O.iter)
# besides unbalanced force evolution, also plot the displacement-force diagram
plot.plots = {'i': ('unbalanced',), 'w': ('Fz',)}
plot.plot()
Is there any mistake is the porosity calculation process?
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