When it comes to documentation, for me it’s: never remove anything, always improve :)
On 21 Feb 2018, 22:25 +0100, Robert Caulk <rca...@eng.ucsd.edu>, wrote: > Hello Jérôme, > > I support clarifying the meaning of particle young in the class reference as > you suggest. There is no doubt that newcomers to DEM and Yade confuse micro > young's modulus with macro young's modulus all the time. > > I would vote for clarifying the general doc instead of full removal of > stiffness and normal stiffness section in general doc, I think they provide > good examples of how Yade treats micro stiffness. If we decide to keep the > sections I can look into improving their clarity. But if others think removal > is best, I am not against it :-) > > Best, > > Robert > > > On Wed, Feb 21, 2018 at 8:59 AM, Jerome Duriez <jerome.dur...@irstea.fr> > > wrote: > > > Hi, > > > > > > After seeing Yet Another Doubts on "young" meaning / > > > Ip2_FrictMat_FrictMat_FrictPhys contact model (a PhD student in my > > > institute), I'm proposing to explicitly mention the underlying equations > > > in the doc, once for all. > > > The corresponding would-be diff appears at the end of the email, you may > > > also compare the attached screenshot with > > > https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Ip2_FrictMat_FrictMat_FrictPhys. > > > From the diff, you will see I'm also proposing to remove the "harmonic > > > average stiffness" comment, for instance because there actually is a "2" > > > factor missing/extra between the comment and the actual code. > > > > > > > > > In the case of the above-mentioned PhD student, confusion also arose > > > because of https://yade-dem.org/doc/formulation.html#stiffnesses and > > > https://yade-dem.org/doc/formulation.html#normal-stiffness. > > > As such, I would also propose to simply remove these two sections from > > > the doc. > > > From my point of view, they actually are too Ip2-specific to appear in > > > the general doc. > > > > > > > > > If necessary, a reference to the (equivalent) 2.2.1 and 2.2.1.1. sections > > > from Vaclav's thesis ([Smilauer2010b] reference) could be introduced e.g. > > > in Ip2_CpmMat_CpmMat_CpmPhys and Ip2_FrictMat_FrictMat_FrictPhys > > > docstrings, to keep track of these comments that could be made concerning > > > the Ip2 equations. > > > > > > > > > This email probably is Yet Another non-critical one, but since it deals > > > about (the doc of) central pieces of code, and lines probably written by > > > Vaclav, I'm opening a possible discussion here before performing the > > > changes. > > > > > > > > > Jérôme > > > > > > PS: next step would be to move > > > https://yade-dem.org/doc/formulation.html#strain-evaluation to Ig2 > > > docstrings but I'm not planning on it... > > > > > > > > > ****************** Diff herein proposed for commit ************** > > > > > > diff --git a/pkg/dem/FrictPhys.cpp b/pkg/dem/FrictPhys.cpp > > > index cb904da..4f8ffe8 100644 > > > --- a/pkg/dem/FrictPhys.cpp > > > +++ b/pkg/dem/FrictPhys.cpp > > > @@ -26,9 +26,7 @@ void Ip2_FrictMat_FrictMat_FrictPhys::go( const > > > shared_ptr<Material>& b1 > > > Real Va = mat1->poisson; > > > Real Vb = mat2->poisson; > > > > > > - //harmonic average of the two stiffnesses when (2*Ri*Ei) is the > > > stiffness of a contact point on sphere "i" > > > Real Kn = 2*Ea*Ra*Eb*Rb/(Ea*Ra+Eb*Rb); > > > - //same for shear stiffness > > > Real Ks = 2*Ea*Ra*Va*Eb*Rb*Vb/(Ea*Ra*Va+Eb*Rb*Vb); > > > > > > Real frictionAngle = (!frictAngle) ? > > > std::min(mat1->frictionAngle,mat2->frictionAngle) : > > > (*frictAngle)(mat1->id,mat2->id,mat1->frictionAngle,mat2->frictionAngle); > > > > > > diff --git a/pkg/dem/FrictPhys.hpp b/pkg/dem/FrictPhys.hpp > > > index eeb2ef4..12c85ee 100644 > > > --- a/pkg/dem/FrictPhys.hpp > > > +++ b/pkg/dem/FrictPhys.hpp > > > @@ -44,7 +44,7 @@ class Ip2_FrictMat_FrictMat_FrictPhys: public > > > IPhysFunctor{ > > > const shared_ptr<Material>& b2, > > > const shared_ptr<Interaction>& interaction); > > > FUNCTOR2D(FrictMat,FrictMat); > > > - > > > YADE_CLASS_BASE_DOC_ATTRS(Ip2_FrictMat_FrictMat_FrictPhys,IPhysFunctor,"Create > > > a :yref:`FrictPhys` from two :yref:`FrictMats<FrictMat>`. The compliance > > > of one sphere under point load is defined here as $1/(E.D)$, with $E$ the > > > stiffness of the sphere and $D$ its diameter. The compliance of the > > > contact itself will be the sum of compliances from each sphere, i.e. > > > $1/(E_1.D_1)+1/(E_2.D_2)$ in the general case, or $2/(E.D)$ in the > > > special case of equal sizes and equal stiffness. Note that summing > > > compliances corresponds to an harmonic average of stiffnesss (as in e.g. > > > [Scholtes2009a]_), which is how kn is actually computed in the > > > :yref:`Ip2_FrictMat_FrictMat_FrictPhys` functor:\n\n $k_n = > > > \\frac{E_1D_1*E_2D_2}{E_1D_1+E_2D_2}=\\frac{k_1*k_2}{k_1+k_2}$, with > > > $k_i=E_iD_i$.\n\n The shear stiffness ks of one sphere is defined via the > > > material parameter :yref:`ElastMat::poisson`, as ks=poisson*kn, and the > > > resulting shear stiffness of the interaction will be also an harmonic > > > average. In the case of a contact between a :yref:`ViscElMat` and a > > > :yref:`FrictMat`, be sure to set :yref:`FrictMat::young` and > > > :yref:`FrictMat::poisson`, otherwise the default value will be used.", > > > + > > > YADE_CLASS_BASE_DOC_ATTRS(Ip2_FrictMat_FrictMat_FrictPhys,IPhysFunctor,"Create > > > a :yref:`FrictPhys` from two :yref:`FrictMats<FrictMat>` as per the > > > following expressions: \n\n$k_n = \\frac{E_1D_1*E_2D_2}{E_1D_1+E_2D_2}$ > > > where $k_n=$ :yref:`FrictPhys.kn`, the $E_i$ are :yref:`FrictMat.young` > > > for each contacting body $i=1;2$, and the $D_i$ are the bodies' > > > (equivalent) diameters\n\n$k_s = > > > \\frac{E_1D_1P_1*E_2D_2P_2}{E_1D_1P_1+E_2D_2P_2}$ where $k_s=$ > > > :yref:`FrictPhys.ks` and the $P_i$ are the bodies' > > > :yref:`FrictMat.poisson`\n\n$\\mu = \\tan(min(\\phi_1,\\phi_2))$ by > > > default (see :yref:`frictAngle > > > attribute<Ip2_FrictMat_FrictMat_FrictPhys.frictAngle>`), where $\\mu=$ > > > :yref:`FrictPhys.tangensOfFrictionAngle` and the $\\phi_i$ are the > > > bodies' :yref:`FrictMat.frictionAngle`.", > > > > > > ------ > > > Chargé de Recherche / Research Associate > > > Irstea, RECOVER > > > 3275 route de Cézanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE > > > +33 (0)4 42 66 99 21 > > > > > > A free DEM conference in April: https://2ndyadeworkshop.sciencesconf.org/ > > > > > > > > > _______________________________________________ > > > 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 >
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