# confinement condition

18 views
Hi Vaclav,

Happy new year!!!

I would like to ask about the methods of confinement. I have concrete packing in cylindrical shape and I would like to block outer particles at outer layer not to move in x and y direction (meanwhile I applied the force on the top in z- direction). Would it be sufficient if I just block them as :

for s in outerLayer: s.blocked = 'xy'

or shall I introduce a frictionless cyclindrical wall with very high stiffness surrounding the specimen? I personally think the first approach is simpler,

Best,

Giao

answered Jan 23 by (49,030 points)
selected Jan 24

Hi Giao, sorry for late response (again ;)) ). The first approach is simpler but it might prevent localization (crack development -- particles would like to move the x-y plane there), if you go that far with the load. Frictionless wall is good, though don't overshoot it with the density, it would reduce critical timestep; usually if you consider the same stiffness as the sample itself, it should be sufficient. Best regards, Vaclav
commented Jan 24 by (500 points)

Thank you Vaclav,

your support helps, as always! For the Frictionless wall, I use the following codes:

wallMat= FrictMat(young=20e8,ktDivKn=.0)
wall = woo.utils.wallBox(sp.aabb(),mat=wallMat,which=(1,1,1,1,1,0))

S.engines= [
#ForceResetter(),
Leapfrog(damping=DAMP_,reset=True,kinSplit=True),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Wall_Aabb(),Bo1_Facet_Aabb()]),
ContactLoop([Cg2_Sphere_Sphere_L6Geom(),Cg2_InfCylinder_Sphere_L6Geom(),Cg2_Facet_Sphere_L6Geom(),Cg2_Wall_Sphere_L6Geom()],
[Cp2_ConcreteMat_ConcretePhys(),Cp2_FrictMat_FrictPhys()
#Law2_L6Geom_FrictPhys_IdealElPl#noSlip=true
],
[Law2_L6Geom_ConcretePhys(yieldSurfType='lin',omegaThreshold = 0.999,epsSoft=ComPlas['Eps_pl'],relKnSoft=ComPlas['K_s']

)#,Law2_L6Geom_FrictPhys_IdealElPl(label='law')
]
),


I still dont understand the difference between wall and facet, is it important to set Density value for wall?

Regards,
Giao

commented Jan 24 by (49,030 points)

Walls are always global-axes-aligned (see Wall.axis parameter, and Wall.sense) and infinite, whereas facets are triangles (with arbitrary orientation, with active boundary). So use Walls if you can (all computations easier). Density does not matter for Walls, it is used for mass computation, and Walls cannot be integrated as a normal solid (being infinite, inertia being ill-defined). HTH, Vaclav

commented Jan 24 by (500 points)
reshown Feb 18 by eudoxos

Hi Vaclav,
Now that I tried the second approach, from the force flow it seems to me that the wall did nothing to prevent lateral expansion of my model, at later stage, the particle penetrate the wall and 'flying' away'. I did some inspect and it seem like the engine kinda ignoring them.

Could you help me to make the wall works properly?

Giao

commented Feb 18 by (49,030 points)

Giao, sorry for overlooking this post. Did you manage to make it work in the end? v.