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[Christian Jakob <question235138@xxxxxxxxxxxxxxxxxxxxx>]

Question #235138 on Yade changed:
https://answers.launchpad.net/yade/+question/235138

Christian Jakob proposed the following answer:
Hi,

> how ever, i have some additional development during the simulation. an error named 
> " FATAL /build/buildd/yade-0.70.0/core/ThreadRunner.cpp:31 run: Exception occured:
> Body #37 has velocity==NaN! "
> occured and this automatically terminates the simulation.
>
> do you know anything that could be the cause of this problem and how to fix it?.

1.) follow statements/remarks of jduriez and do something like:

idSand=O.materials.append(..........,label='sandLabel'))

Then you can do:

sandLabel.young=1e6

or

O.materials[idSand].young=1e6

which is doing the same ...

But changing the property of a material will not change material properties of existing bodies.
Do you want to change material properties during the run?


2.) If your simulation is dynamical, time step could be too high. Decrease it either directly with a fixed O.dt= ...? or decrease timestepSafetyCoefficient in GlobalStiffnessTimeStepper engine.


Additionally I want to say, that GravityEngine is deprecated. You can
set it directly in the NewtonIntegrator

NewtonIntegrator(gravity=(0,0,-9.81),damping=0.7,label='integrator')

and remove this line:

GravityEngine(gravity=(0,0,-9.81)),

Next time please send a short example script, that shows the problem. It
is quite time consuming investigating a 1000-line script including 950
irrelevant lines.

Regards,

Christian

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