Apply force only once

Hi Laura

> My first choice was to put a high period (100000000 for example), but
> this way , the green sphere falls on the surface of spheres before the
> force was applied .

I think that the force was applied correctly. The only problem is that the
force was was applied for one time step (I assume very short time), so it
has almost no effect..

> What I need is to apply a force on green particle
> when it is "in the air " to describe a parabolic movement to fall on the
> surface and stop.
>

From this sentence, I am not sure if applied force is really what you are
looking for.. Wouldn't setting initial velocity in x direction be OK? The
resulting trajectory would be parabola..

cheers
Jan

Hi Jan, thanks for your reply!

Respect "I think that the force was applied correctly. The only problem is that the
force was was applied for one time step (I assume very short time), so it
has almost no effect.." You were right . I've changed the IterPeriod and the value of O.force, and works ok.

PyRunner(command='force()',
  iterPeriod=1000000,initRun=True,label='checker'),

def force():
 piedraensayo=[]
 for i in range(0,len(O.bodies)):
  b=O.bodies[i]
  if O.bodies[i].shape.color==(0,1,0):
   piedraensayo.append([i])
   id_ball=i
   fx=10000
   fy=0
   fz=0
   O.forces.addF(id_ball, (fx, fy, fz))

However, maybe I should apply a velocity in x direction. In this sense, I tried this, and not working. The problem is I don't know how putting the identity of the green sphere to apply the velocity vector only on her.

def force():
 piedraensayo=[]
 for i in range(0,len(O.bodies)):
  b=O.bodies[i]
  if O.bodies[i].shape.color==(0,1,0):
   piedraensayo.append([i])
   id_ball=i
   b.state.vel(id_ball,(1,0,0))

Error: b.state.vel(id_ball, (10,0,0))
TypeError: 'Vector3' object is not callable

Thanks for your help , as always! =)

Hi Laura,

> I've changed the IterPeriod and the value of O.force, and works ok.
>

I believe it works, but I would not use it this way :-)

                        b.state.vel(id_ball,(1,0,0))
> Error: b.state.vel(id_ball, (10,0,0))
> TypeError: 'Vector3' object is not callable

the syntax should be:

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

use this line only once in the beginning of the simulation (preferably do
not use PyRunner). Otherwise it would overwrite the vertical component of
the motion. (To test it, you can use PyRunner as you have it now with
initRun=True and iterPeriod=someVeryBigNumber)

cheers
Jan

Hi Jan, thanks again!

I don't understand what do you say about put the b.state.vel at the begin of the simulation without use PyRunner. What type of function should I write in the script for identify the green sphere and then apply the vector velocity in this sphere? Sorry for question, could be a own mistake in my way of do the script.

cheers,

Laura

Hi Jan,

Solved!!
 I made the identification of waiting in the terminal , apply the rate in the field , and then start the simulation , which saves the position and speed of the stone with the PyRunner for storing data.

Thanks for the help. Regards =)

Laura

Hi Jan,

Solved!!
 I made the identification of waiting in the terminal , apply the rate in the field , and then start the simulation , which saves the position and speed of the stone with the PyRunner for storing data.

Thanks for the help. Regards =)

Laura

Hi Laura

I mean something like this:

#########################################
O.load('/path/spheresurface.yade')

MatBal=O.materials.append(FrictMat(...))

### green sphere
greenSphere = sphere((0.108,0.2289647116,0.7175),0.0199647116,color=(0,1,0),material='mat1')
# no need of utils.sphere
greenSphereId = O.bodies.append(greenSphere)

def guardar():
        ...

O.engines=[
        ForceResetter(),
        InsertionSortCollider(
                [Bo1_Sphere_Aabb(),
                        Bo1_Facet_Aabb(),
                        Bo1_Box_Aabb(),
                        Bo1_Wall_Aabb()]),
        InteractionLoop(
                [Ig2_Sphere_Sphere_ScGeom(),
                        Ig2_Facet_Sphere_ScGeom(),
                        Ig2_Wall_Sphere_ScGeom(),
                        Ig2_Box_Sphere_ScGeom()],
                [Ip2_FrictMat_FrictMat_FrictPhys()],
                [Law2_ScGeom_FrictPhys_CundallStrack()]
        ),
        # PyRunner(command='force()',
        # iterPeriod=1,initRun=True,label='checker'), # this
PyRunner will not be used
        PyRunner(command='guardar()',
                iterPeriod=1,initRun=True,label='checker'),
        NewtonIntegrator(damping=0.5,gravity=(0,-9.81,0),label='newton'),
        yade.qt.SnapshotEngine(fileBase='3d-',iterPeriod=
1000,label='snapshot')
]
O.dt=utils.PWaveTimeStep()

greenSphere.state.vel = (1,0,0) # this :-)
#################################################3

cheers
Jan

2015-06-30 15:31 GMT+02:00 rayolau <email address hidden>:

> Question #268691 on Yade changed:
> https://answers.launchpad.net/yade/+question/268691
>
> rayolau posted a new comment:
> Hi Jan, thanks again!
>
> I don't understand what do you say about put the b.state.vel at the
> begin of the simulation without use PyRunner. What type of function
> should I write in the script for identify the green sphere and then
> apply the vector velocity in this sphere? Sorry for question, could be a
> own mistake in my way of do the script.
>
> cheers,
>
> Laura
>
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I don't understand the details but for the record:

- applying a force for one step is: O.forces.addF(id_ball, f)
- applying a force permanently is: O.forces.addF(id_ball, f,permanent=True)