How to integrate motion in only one direction?

I guess maybe I can set the dynamic of this clump is false and write a one-dimensional newton-integrator for the clump.

Hi Guo,

You can block all degrees of freedom, except for 'z'. Let's say 'b' is your body, so:

b.state.blockedDOFs='xyXYZ'

the above code constrains body, and allows only for vertical movement (capital letters control rotation).

Best wishes,
Karol

Hi Karol,
Thank you very much for your reply.
I've tried to use this function to block DoFs. But it didn't work.

This is part of my code. The clump's DoFs weren't blocked.

OutDiameter=0.1143

PipeRoughR=0.01

SectionNum=20

LongNum=15

WidthX=0.6

HeightZ=3

HeightZ0=0.3

thickness=0.01

gravity=(0,0,-10)

densityPipe=7850

InputR=OutDiameter/2-PipeRoughR

Gap=sin(pi/SectionNum)*2*InputR

LengthY=Gap*(LongNum-1)+PipeRoughR

PipeParticleNum=0

PP=[]

for j in range(LongNum):

    for i in range(SectionNum):

        PipeParticleNum += 1

        PP.append(sphere([InputR*sin(i*2*pi/SectionNum)+0.3,j*Gap,InputR*cos(i*2*pi/SectionNum)+0.3],radius=PipeRoughR,,color=(1,1,0)))

PPID=O.bodies.appendClumped(PP)

PPClump=O.bodies[PPID[0]]

PPClump.dynamic=1

PPClump.state.blockDOFs='xyXYZ'

PPClump.state.vel = (0, 1,0)

PPClump.state.angVel = (0,0,0)

h=0.4

sp=pack.SpherePack()

sp.makeCloud((thickness*5,0.001,h),(WidthX-thickness*5,LengthY-0.001,h+.2),rMean=0.02)

#

sp.toSimulation(material=O.materials[SphereMID])

newton=NewtonIntegrator(damping=0.4,gravity=gravity,dampGravity=0)

O.engines=[

 ForceResetter(),

 #(1) This is where we allow big bodies, else it would crash due to the very large bottom box:

 InsertionSortCollider([Bo1_Box_Aabb(),Bo1_Sphere_Aabb()],allowBiggerThanPeriod=True),

 InteractionLoop(

  [Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],

  [Ip2_FrictMat_FrictMat_FrictPhys()],

  [Law2_ScGeom_FrictPhys_CundallStrack()]

 ),

 GlobalStiffnessTimeStepper(),

    newton,

]

for b in O.bodies:

    if isinstance(b.shape,Sphere):

        b.state.vel[2]=-1

Thank you.

Yours sincerely,
GUO

OK. Thank you very much.
One more small question: why is there no warning when I write a wrong code?

It is because you can give a new attribute to the body this way. For example, if you want to discriminate between groups of bodies, you can do something like this.

###
if b.state.pos[2]<z1:
    b.shape.belongsTo = 'bottom'
###

belongsTo is an attribute that I have just made up.

Cheers,
Karol

OK. I get it.
Thank you very much.

Yours sincerely,
GUO

Thanks Karol Brzezinski, that solved my question.