New question #253399 on Yade:
https://answers.launchpad.net/yade/+question/253399
Hi all,
I am simulating flows of particles due to an external fluid force. Then, the
phenomenon is dynamic, I use periodic boundary condition in the streamwise
direction and I have particles with velocity as high as 0.5m/s.
I noticed a problem of stability when considering small periodic cell. After
some times to isolate the problem, I found out that the problem arises when a
particle travel for more than 10 times the size of the periodic cell. This does
not seem to depend on the contact law, neither on the time step or the velocity
of the particle, but only on the number of time the particle is crossing the
periodic cell. I am not sure but I think this problem was not present some
times ago.
Have you already heard about such a bug ? What can I do to fix that ?
It is a real problem for me as I would be interested to study the effect of the
reduction of the size of the periodic cell and reduce it if possible.
Raphaël
I am using Ubuntu 12.04 and yade daily 1.10.0-72-d9ab58c~precise
Here is a simple script to reproduce the bug :
O.dt = 1e-7
lengthCell = 10 #Streamwise length of the periodic cell in diameter
slope = 0.5 #Angle of the slope in radian
#Particles parameters
diameterPart = 6e-3 #Diameter of the particles, in meter, 6mm here.
densPart = 2500 #density of the particles, in kg/m3
#Contact law
cnPart = 0.0 #Normal viscous damping coefficient.
knPart = 1e4 #Normal stiffness of the particle
partFrictAngle = 0.0 #28 *pi/180 #friction angle of the particles, in radian
csPart = 0 #tangential viscous damping coefficient (=0)
ksPart = 0.5*knPart #tangential stiffness of the contact
##Definition of the materials
O.materials.append(ViscElMat(cn=cnPart, cs=csPart, kn=knPart, ks=ksPart,
density=densPart, frictionAngle=partFrictAngle, label='sphereMat'))
#
#Geometrical configuration
#
length = lengthCell*diameterPart
width = length/2.0
height = length/3.0
g = Vector3(9.81*sin(slope),0,-9.81*cos(slope))
groundPosition = height/3.0
#Definition of the semi-periodic cell
O.periodic = True
O.cell.setBox(length,width,height)
# build the ground
lowPlane = box(center=
(length/2.0,width/2.0,groundPosition),extents=(length*10,width*10,0),fixed=True,wire=False,color
= (0.8,0.8,0.8),material = 'sphereMat')
#Send the ground box and the particle to simulation
O.bodies.append(lowPlane)
O.bodies.append(sphere((length/2.0,width/2.0,groundPosition+diameterPart),radius
= diameterPart*0.5, material = 'sphereMat'))
#########################
#### SIMULATION LOOP#####
#########################
O.engines = [
# Reset the forces
ForceResetter(),
# Detect the potential contacts
InsertionSortCollider([Bo1_Sphere_Aabb(),
Bo1_Wall_Aabb(),Bo1_Facet_Aabb(),Bo1_Box_Aabb()],label='contactDetection',allowBiggerThanPeriod
= True),
# Calculate the different interactions
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(), Ig2_Box_Sphere_ScGeom()],
[Ip2_ViscElMat_ViscElMat_ViscElPhys()],
[Law2_ScGeom_ViscElPhys_Basic()]
),
# Integrate the equation and calculate the new position/velocities...
NewtonIntegrator(damping=0.0, gravity=g, label='newton')
]
O.saveTmp()
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