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[Jan Stránský <question204014@xxxxxxxxxxxxxxxxxxxxx>]

Question #204014 on Yade changed:
https://answers.launchpad.net/yade/+question/204014

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello Christian,


> i'm not sure if i have to use the utils.PWaveTimeStep() in my case. I want
> to simulate a facetbox which is rotating around the z-axes and enclosed by
> a pack of spheres . Therefore i want to record the force which acts on the
> facetbox.
>

if you use non-dynamic facets, then it is ok to use utils.PWaveTimeStep.
The critical time step is computed for minimal possible (reasonable)
interaction length (i.e. sphere radius), so also interaction sphere-facet
(where the interaction length should equals radius) should behave stable
for such time step.

The requirement of spherical bodies is due to internal implementation..


> The ducumentation says that the utils.PWaveTimeStep() makes some
> simplifications, like
> * all particles are spherical and have the same radius R;
> * the sphere's material has the same E and ρ
>
>
where did you find these information? I was not able to find it :-)


> All of my spheres have the same radius, but i use a facet as well. And i
> have seen that the utils.PWaveTimeStep() in some examples with facets and
> spheres. So i'm still wondering if i can use the utils.PWaveTimeStep() in
> my case? Or should i use GlobalStiffnessTimeStepper because i use a facet?
>

then it depends on the speed of your facets. If for example for the wave
critical time step the facets would move through 3 spheres, then you should
reduce it. But GlobalStiffnessStepper would not help in this case (as from
the stiffness point of view the pwave time step will be ok)

I hope I formulated the answer in understandable way, if not, don't
hesitate to ask again :-)

Jan

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