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[Bruno Chareyre <question429604@xxxxxxxxxxxxxxxxxxxxx>]

Question #429604 on Yade changed:
https://answers.launchpad.net/yade/+question/429604

    Status: Open => Answered

Bruno Chareyre proposed the following answer:
>  I also want the normal one

Very easy to find. Will you really waste cpu time in calculating the
incident shear twice when you actually only need the normal one (you
already have the shear one with my suggestion).

>contact point is always considered to be situated at the middle of the
penetration depth. While this is ok for particles of the >same size,
this to my opinion does not apply when considering the interaction of a
particle with a wall. My question was (and >still is): why is it
necessary to use this trick/approximation to avoid the bug ?

I'm not following you fully. 1/ I don't see a trick/approximation, to me
it is just ordinary code. So when you ask "why" I tend to just think
"why not?".  2/ why do you think it is irrelevant to include the 0.5*un
term in the branch between e.g. sphere and box or spheres of different
sizes? How would you like it? Did you realize that the same 0.5 is also
used between facets and spheres whatever the law functor?

> I believe it is not a good idea to leave this contact law with a
mistake

You are right there is nothing wrong in fixing existing code and you are very welcome to do it.
However, guess why ViscElPhys_Basic has a bug that CundallStrack does not have? Because they are two different functors instead of one, i.e. more lines of code with less eyes/fingers for each of them. Hence if someone wants to do something very useful for the years to come he could merge some of the existing functors. That was my point.
Cheers
Bruno

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