# yade-users team mailing list archive

## [Question #235628]: Trace a force under the capillary stress

```New question #235628 on Yade:

Hello all,

I am trying to trace a capillary force between two particles under the capillary stress.
However, I have got a zero force between two particles even though the particles are pulling each other.
So, I am wondering whether the force I am using in the script does not include the capillary force.
If not, is there other function I can use to trace a capillary force?
In addition, I would like to compare the capillary force from my hand calculation in order to ensure that the module is working.

h = 0.0001 #praticle distance

#create two sphere paticles#
O.bodies.append([
utils.sphere((0,0,2*r+h),r)
])

#define engines#
O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=2)]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=2)],
[Ip2_FrictMat_FrictMat_MindlinCapillaryPhys()],
[Law2_ScGeom_MindlinPhys_Mindlin(neverErase=True)]
),
Law2_ScGeom_CapillaryPhys_Capillarity(capillaryPressure=10000,label='Cap'),
NewtonIntegrator(damping=0.4,gravity=(0,0,0)),
]

Cap.createDistantMeniscii=True
O.run(1,True)
Cap.createDistantMeniscii=False

#d0 = O.bodies[0].state.displ()
#d1 = O.bodies[1].state.displ()

f0 = O.forces.f(0)
f1 = O.forces.f(1)

#plot.plots={'i':('b0displ')}
plot.plots={'i':('f0forces')}
plot.plot()
plot.live=True
plot.autozoom=True
O.dt=0.5*PWaveTimeStep()
qt.View()
O.saveTmp()

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