Václav Šmilauer a écrit :
Just to say to be carefull with formula in Hentz's thesis: the idea
was to use as inputs for contact properties the Young modulus and
Poisson ratio that we want to obtain macroscopically for the granular
assembly. The "funny term" are use to compute kn and ks with respect to
these macroscopic Young modulus and Poisson ratio
Yes, I know. I disregarded that funny term, it is close to 1.0 and
doesn't play any role.
What struct me, though, was that we deviate from any obvious definition
of contact stiffness. Its dimensionality is correct, but it is scaled by
some dimensionless constant (π/2 in our case) away from the "intuitive"
definition (which is the base of what Hentz uses): stiffness of cylinder
with radius min(r₁,r₂) between spheres' centers, with some average
Young's modulus.
I say nothing if such constant is properly documented and supported by
some reasoning, but for me now, even though it works, it is just garbage
code.
In my opinion, the only important point is to compute kn and ks such as
scale effects are avoided, and I think it is well done in the current
formula (*) in Yade.
I disagree with the premise that the only important point is to avoid
scale effects. I like quantities to have physical meaning, as much as it
is meaningful with discrete models; the argument (Bruno ;-) ) that
discrete solution doesn't converge (and doesn't approach continuous
solution) if you refine "mesh" (packing) does not justify, in my eyes,
gratuitously introducing random constants to the code.
Besides that, imagine Chiara reading that code (in a few days)... guess
what happens? ;-)
v
Well, I understand your point of view Vaclav. I just know that the
parameter kn/Ds (where Ds is the sphere diameter) is a well admitted
parameter in the DEM community to evaluate the contact stiffness of a
granular assembly, especially to compare this stiffness with respect to
the mean pressure applied to the assembly through the dimensionless
parameter Kappa = kn / (Ds p), where p is the mean pressure.
Nevertheless, I imagine, you will tell me that is not a good argument ;-)
Best,
Luc
_______________________________________________
Mailing list: https://launchpad.net/~yade-dev
Post to : [email protected]
Unsubscribe : https://launchpad.net/~yade-dev
More help : https://help.launchpad.net/ListHelp
--
Luc Sibille
Université de Nantes - Laboratoire GeM UMR CNRS
IUT de Saint Nazaire
58, rue Michel-Ange - BP 420
44606 Saint-Nazaire Cedex, France
Tel: +33 (0)2 40 17 81 78
_______________________________________________
Mailing list: https://launchpad.net/~yade-dev
Post to : [email protected]
Unsubscribe : https://launchpad.net/~yade-dev
More help : https://help.launchpad.net/ListHelp
