# yade-users team mailing list archive

## [Question #676528]: Experimental behaviour is different from simulated one

```New question #676528 on Yade:

Hi everyone,
I've done some tests in laboratory and I'm trying to reproduce the experimental behaviour using YADE but there is something that I don't understand.
The geometry of the problem is the following:
There is an hollow aluminum cylinder  fixed to the ground and filled with 20000 aluminum alloy spheres (granular material). An object (named "intruder") , almost in contact with the granular material, is let free to fall inside the cylinder with a given initial velocity ( lets say impact velocity). The objective is to dissipate its kinetic energy by means of the granular material. The problem is that the granular material seems to dissipate the kinetic energy in really more efficient way than what happens in laboratory.
I'm using the following values for the materials:

idIntruder  = O.materials.append(FrictMat(young=80e9,poisson=.33,frictionAngle=.3,density = 2700,label="intruder"))
idCylinder  = O.materials.append(FrictMat(young=80e9,poisson=.33,frictionAngle=.3,density = 2700,label="cylinder"))
idSphere    = O.materials.append(FrictMat(young=72e9,poisson=.33,frictionAngle=.3,density = 2690,label="sphere"))

and the engine is like this:

O.engines=[ForceResetter(),InsertionSortCollider([Bo1_Sphere_Aabb(),
Bo1_Box_Aabb(),
Bo1_Polyhedra_Aabb()]),
InteractionLoop([Ig2_Sphere_Sphere_ScGeom(),
Ig2_Box_Sphere_ScGeom(),
Ig2_Facet_Polyhedra_PolyhedraGeom(),
Ig2_Wall_Polyhedra_PolyhedraGeom(),
Ig2_Sphere_Polyhedra_ScGeom()],
[Ip2_FrictMat_FrictMat_FrictPhys()],
[Law2_ScGeom_FrictPhys_CundallStrack()]),
NewtonIntegrator(gravity=(0,0,-9.81)),
VTKRecorder(iterPeriod=37000,recorders=['spheres','boxes','force','stress'],fileName=O.tags['id']+'/'+'vtk'),
PyRunner(command="vtkExporter.exportSpheres(ids='all',what=['Sphere_forces','abs(O.forces.f(b.id))'])",iterPeriod=1000),
PyRunner(command="vtkExporter.exportPolyhedra(ids='all')",iterPeriod=37000),
PyRunner(command='stopper()',iterPeriod=1000),