yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Hi

I'm trying to adapt the capillary law to the current contact logic. I'm 
explaining the problem below in case somebody has suggestion (and this 
may serve as an exemple for similar situations with multiple interactions).

Currently, solid contacts + capillary forces are handled using one 
unique interraction physics in which we have data for both elastic law 
and capillary law. Then, ElasticContactLaw and CapillaryLaw are applied 
sequentially at each iteration.

The problem :
ElasticContactLaw is "requestingDeletion" as soon as there is no 
contact, when CapillaryLaw should still do something on the same 
interaction.

Old solution :
- ElasticLaw was applied first, and could set "isReal=false" when no 
contact exist
- After that, in the same cycle, capillary law could revert this flag, 
so that the interaction geometry was still computed in the next time step.

Now this solution is not possible because requestDeletion() cannot be 
reverted.

I see different alternatives, but all of them need to disable, or 
modify, the code in which the command "requestDeletion()" appears.
The problem is this happens in functors, like 
ef2_Spheres_Elastic_ElasticLaw. So, it is impossible to change this in 
only one place for all.

What I have in mind now is to add a bool to the parameters of functors 
(the one I use), and a flag in ElasticContactLaw that would be passed to 
functors :

- ef2_Spheres_Elastic_ElasticLaw(..., bool allowDelete=true)

By setting this flag false, ElasticLaw will stop deleting anything. Only 
CapillaryLaw would delete interactions.
This is for a quick solution.

For a more general solution with N interaction laws (*), we could just 
decide that colliders will erase interractions only if no constitutive 
law need it.
For this purpose, the function "requestDeletion" could be replaced by 
"requestKeep", and all interactions would be deleted unless *at least 
one* constitutive law decides otherwise. In this case, the "allowDelete" 
flag is not needed any more.

What do you think of this?

Bruno


(*) I recall all laws must use the same unique type of interactions, 
since Yade does not handle multiple interactions between two bodies. 
This is not a big problem with multiple inheritance. If I want 
electric(**), elastic, and capillary interactions between bodies, I can 
simply define a IPhysics class like this :

class ElectroElasticCapillaryInteraction: public 
ElasticContactInteraction, public ElectricInteraction, public 
CappilaryInteraction
{ ...

A unique constitutive law inheriting from the "N" individual 
constitutive laws is possible as well (it doesn't solve the initial 
problem, since "requestDeletion" is inside functors).

(**) No... I did not implement any electric law yet...




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Chareyre Bruno
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