Hi all, thanks for the active discussion. So I guess we just leave it as it is and use 2 for boxes and facets if this is the usual assumption. No problem. And introducing r->infinity ignores the material properties of the facet, so I guess my suggestion was not the best one however mathematically correct ;-)
Thanks again! Klaus On Tue, 13 Dec 2011 10:10:08 PM Bruno Chareyre wrote: > I have no explanation for the 2*refR other than that: > - there was 2*refR in box-sphere interactions a while ago (I don't know > why), > - facet-sphere interactions inherited this 2* from box-sphere > interactions (my assumption). > > The thing is I changed that in box-sphere, and now refR of a box is the > radius of the sphere. I can at least invoke symmetry to justify this. > Infinite radius could be justified too, the problem is it would give > contacts twice stiffer than the contacts between spheres, hence smaller > timestep, without clear advantage. > > Bruno > > On 13/12/11 11:35, Klaus Thoeni wrote: > > Everyone on holidays already? > > > > Well I am still wondering why for the calculation of the stiffness of a > > sphere and a facet the radius of the facet is assumed to be twice the > > radius of the sphere. This is basically the value comming from > > GenericSpheresContact. In my opinion it doesn't make sense. The facet > > can be seen as a sphere with radius infinity. So if we take the harmonic > > average (as it is done in > > Ip2_FrictMat_FrictMat_FrictPhys ) considering e.g. rb->infinity the > > stiffnesses become kn = 2*Ea*ra and ks = 2*Ea*ra*Va. > > > > You agree? If so I could commit the changed code. Please let me know. > > > > On Sun, 11 Dec 2011 06:38:35 PM Klaus Thoeni wrote: > >> Hi Guys, > >> > >> what value for refR does the GenericSpheresContact return for a facet? > >> By introducing TRVAR2( Ra, Rb ) e.g. in > >> Ip2_FrictMat_FrictMat_FrictPhys::go it seems if a sphere is > >> intersecting with a facet the refR value for the facet is just 2*refR > >> of the sphere. Is this true? And when yes, what's the reason? It's > >> fundamental for kn and ks, isn't it? > >> > >> Thanks, > >> > >> Klaus > >> > >> _______________________________________________ > >> Mailing list: https://launchpad.net/~yade-dev > >> Post to : yade-dev@lists.launchpad.net > >> Unsubscribe : https://launchpad.net/~yade-dev > >> More help : https://help.launchpad.net/ListHelp > > > > _______________________________________________ > > Mailing list: https://launchpad.net/~yade-dev > > Post to : yade-dev@lists.launchpad.net > > Unsubscribe : https://launchpad.net/~yade-dev > > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : yade-dev@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
