yade-users team mailing list archive

[Jan Stránský <question214773@xxxxxxxxxxxxxxxxxxxxx>]

Question #214773 on Yade changed:
https://answers.launchpad.net/yade/+question/214773

Jan Stránský proposed the following answer:
Hello guys,

thanks to Eugen for summary. Based on his answer (I did not checked the
scripts in detail myself):

the free falling is the same for both contact laws (besause there is no
contact :-).

Then there is a short contact impulse causing force acting on particles
causing their acceleration. The contact laws / parameters may be (and
according to the results they are) different, resulting in different
forces. With different forces the acceleration is also different. But under
assumption of low energy dissipation, the velocity before and after the
contact is the same for any contact law. The difference is the time of
actual contact (for stiffer law it is shorter). But in your simulation this
time is negligible compared to the total time of simulation, therefore you
do not see differences in velocities / positions (at least in the
beginning), although they are there. And also there may be some energy
dissipation in MindlinPhys, I don't know.

Hope it helps you.
Jan


2012/11/21 Eugen Kubowsky <question214773@xxxxxxxxxxxxxxxxxxxxx>

> Question #214773 on Yade changed:
> https://answers.launchpad.net/yade/+question/214773
>
>     Status: Open => Answered
>
> Eugen Kubowsky proposed the following answer:
> Hi Guys,
> I think I know what confuses you.  If I take a look at your python script,
> your simulation is a rather simple experiment. One sphere drops from a
> given height without any initial velocity to ground. Reaching ground it
> jumps up again but with less altitude - drops again and so on and so on.
> Looking at your graphs, we see, that positions as well as velocities are
> roughly the same for Cundall and Hertz at least for t <=0,45.
> But the graphs of forces are completely different. You have about 400N at
> Cundall and about 70N at Hertz.
>
> Thats why you're confused I guess: how can velocities and positions be
> roughly the same for that different forces.
>
> I'm sorry, but I cant help you with that. But maybe it helps someone to
> understand your problem.
>
> Greetings, kubeu
>
> --
> You received this question notification because you are a member of
> yade-users, which is an answer contact for Yade.
>
> _______________________________________________
> Mailing list: https://launchpad.net/~yade-users
> Post to     : yade-users@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~yade-users
> More help   : https://help.launchpad.net/ListHelp
>

-- 
You received this question notification because you are a member of
yade-users, which is an answer contact for Yade.