yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> Hi, all.
> Is anybody uses clumps for now?
>   
I don't, but I would like to soon.
> Seems that clumps incorrectly implemented now.
> For example, in NewtonDampedLaw.cpp line 28:
> 00028         const Vector3r& m=ncb->bex.getTorque(memberId); const
> Vector3r& f=ncb->bex.getForce(memberId);
>
> so m and f in global coord. But line 31:
>
> 00031         Vector3r
> diffClumpAngularAccel=diagDiv(m,clumpRBP->inertia)+diagDiv((rb->se3.position-clumpRBP->se3.position).Cross(f),clumpRBP->inertia);
>
> clumpRBP in local clumps coord.
>   

I would not be surprised to find mistakes or inconsistencies here and 
there as I think Vaclav developped the framework but did not really use 
it for now.

If nothing changed since last time we discussed that in Grenoble, you 
could also find the definition of clumps inertia a bit weird : it is the 
inertia of a sphere of equivalent mass (I suggested that for 
quasi-static problems it would be an acceptable approximation, and it 
was easier to code, so...).

Consequence of that : clumpRBP->inertia is an isotropic matrix, 
independant on the coordinate system, and equations above are correct. :)

If somebody takes time to compute the correct inertia matrix, then 
inertia will have to be rotated, I agree.

Bruno








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Chareyre Bruno
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