Hi Bruno, I was reading code of GSTS trying to write down what it computes. Do you have some paper for reference?
1. Concerning per-body stiffness, we have diagonal terms of the stiffness matrix Kii=(kn-kt)*ni²+kt. If I understand right, the "rotational stiffness matrix" are non-diagonal terms of K, i.e. Kij=(ni² +nj²)kt*r for i≠j. Summing rigidities of all contacts gives per-body rigidity, that's clear. Now, e.g. in http://www.fisica.ufc.br/hans/p/256.pdf (please swallow the fact that they use (1), that is not important now) eq. (16) gives local rigidity proportional to (Kn N ⊗ N)+(Kt T^T T) where N and T are projection tensors defined in (5). Now, I am not able to make up my mind whether these two definitions are equivalent (neglecting the difference kn vs. Kn). Can you enlighten me on that? 2. If I see correctly, computation of timestep from rotational stiffness is mathematically incorrect; e.g. line 39: dtx = sdec->inertia.X()/Rstiffness.X(); as it mixes up inertia.X() in local frame and Rstiffness.X() in global frame. For spherical particles, that makes no difference, of course. Cheers, v. _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
