New question #684756 on Yade:
https://answers.launchpad.net/yade/+question/684756
Hi,
I am currently developing a "traceEnergy" feature in the
Law2_SCG_KnKsPBPhys_KnKsPBLaw for the Potential Blocks and I could use some
advice. :) I am trying to make the implementation as close to existing ones for
other constitutive laws, as possible, in order to keep programming similarity
and make future maintenance easier, so I would like to have your opinion.
#Question 1:
To calculate the plastic dissipation due to friction for a sliding contact, I
see in the Law2_ScGeom_FrictViscoPhys_CundallStrackVisco [1]:
Real dissip=((1/phys->ks)*(trialForce-shearForce))/*plastic disp*/
.dot(shearForce)/*active force*/;
if (traceEnergy) plasticDissipation += dissip;
else if(dissip>0)
scene->energy->add(dissip,"plastDissip",plastDissipIx,/*reset*/false);
The same exists in other constitutive laws, e.g. in ElasticContactLaw.cpp and
Polyhedra.cpp.
Why do we only check the sign of "dissip" when we are about to add it in the
O.energy module (i.e. traceEnergy=False), but not when we are about to add it
in the OpenMPAccumulator "plasticDissipation" (i.e. traceEnergy=true)?
#Question 2:
In the Law2_SCG_KnKsPBPhys_KnKsPBLaw, we consider dissipation due to viscous
damping in the normal direction. Would you suggest I create an
OpemMPAccumulator "normDampDissip", like in the HertzMindlin implementation [2]
and use "traceEnergy" to decide where to store this, like above (i.e. either in
the OpemMPAccumulator or in O.energy), or was "traceEnergy" conceived to be
used only to decide where to store the plastic dissipation due to friction?
Also, when I add this dissipation to O.energy, should I check its sign, like we
do for "dissip" above, and do you think it would be more convenient to reset
the value in every timestep, or monitor the cumulative value (i.e.
reset=false), like we do for the dissipation due to friction?
#Question 3:
In the Law2_SCG_KnKsPBPhys_KnKsPBLaw, after we calculate the normalViscous
force, we deduct it from the normal force [3]:
phys->normalForce -= phys->normalViscous;
When I calculate the elastic potential energy, should I consider the reduced
potential energy or the originally elastic one? i.e.
Reduced potential energy:
scene->energy->add(0.5*(phys->normalForce.squaredNorm()/phys->kn+phys->shearForce.squaredNorm()/phys->ks),"elastPotential",elastPotentialIx,/*reset*/true);
Elastic potential energy :
scene->energy->add(0.5*((phys->normalForce+phys->normalViscous).squaredNorm()/phys->kn+(phys->shearForce+phys->shearViscous).squaredNorm()/phys->ks),"elastPotential",elastPotentialIx,/*reset*/true);
Apologies in advance for not opening three different questions; I just feel
these should be in one thread, as they concern a very specific part of the
source code.
Many thanks,
Vasileios
[1]
https://gitlab.com/yade-dev/trunk/blob/master/pkg/dem/FrictViscoPM.cpp#L210-212
[2] https://gitlab.com/yade-dev/trunk/blob/master/pkg/dem/HertzMindlin.cpp#L365
[3] https://gitlab.com/yade-dev/trunk/blob/master/pkg/dem/KnKsPBLaw.cpp#L228
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