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[Alexander Smith <question256283@xxxxxxxxxxxxxxxxxxxxx>]

Question #256283 on Yade changed:
https://answers.launchpad.net/yade/+question/256283

    Status: Answered => Solved

Alexander Smith confirmed that the question is solved:
Hi Bruno and Chiara,

Thanks for the heads up about facets. It is easily avoided in most cases
by using a corner. A quick fix for now.

I have found why damping was not present. Non-linear damping uses
instantaneous critical damping where the "equivalent" mass is calculated
as:

Real mbar = (!b1->isDynamic() && b2->isDynamic()) ? de2->mass :
((!b2->isDynamic() && b1->isDynamic()) ? de1->mass :
(de1->mass*de2->mass / (de1->mass + de2->mass)));

In the case of two spheres it works fine if either (or both) are
"fixed". However, if one body is a facet and the contacting sphere is
"Fixed" as was the case in the script above, then the equivalent mass is
zero. Hence the damping coefficients are zero.

I also checked the Hertz Mindlin rolling friction model and I can
confidently say that it behaves on a facet exactly as expected for
suitable model parameters (it matches the results produced by Wensrich
and Katterfeld in "Rolling friction as a technique for modelling
particle shape", 2011). Though I am not suggesting PFC3D is a good
benchmark :-)

Thank you both for your help. It is much appreciated.

Alex

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