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R: Re: R: Re: Contact detection


Hi Luc,

I will deal with a dynamic problem and the global geometry is expected 
to change a lot during the simulation. 
Could you suggest me some papers where 
I can find an example in which the SPA was used? Or a reference where it is 
said that this contact detection method is fast or that it is fast according to 
a specific kind of problem? Do you know other DEM softwares that are using the 

Many thanks,


>----Messaggio originale----
>Da: luc.sibille@univ-
>Data: 16/11/2009 17.58
>A: <yade-users@xxxxxxxxxxxxxxxxxxx>
Re: [Yade-users] R: Re:  Contact detection
>   I coming back again 
about the contact detection, actually in SDEC 
>there was the choice between a 
contact detection by grid and the 
>simplest method  were "every particles was 
checked with every particles" 
>because detection by grid is not always the 
fastest method, that depends 
>on what you are simulating:
>1/ When the 
global geometry of your problem is more or less constant 
>during the whole 
simulation (for instance: simulation of a triaxial 
>compression on a dense 
granular assembly) the detection by grid is quite 
>good, because you build the 
grid once at the beginning of the simulation 
>and you use the same grid during 
the whole simulation. In addition you 
>don't have to update the list of the 
neighbouring particles too often.
>2/ When the global geometry of your 
problem is not really fixed (for 
>instance an avalanche of particles in a very 
open space: you don't know 
>a priori were the avalanche will propagate) it is 
not sure if the 
>detection by grid will be good, because you will have to 
update often 
>the grid to follow the particles or you will have to make an 
inital very 
>large grid, whereas only few cells of the grid will be used at a 
>time step for the detection.
>Chiara, I read your mails quite quickly 
so I don't remember if you have 
>specified the kind of simulation you want to 
do, but in my opinion 
>contact detection is good, but not always ;-)

>   Luc
>Janek Kozicki a écrit :
>> Václav Šmilauer said:     (by the date 
of Mon, 16 Nov 2009 09:46:52 +0100)
>>>>>> In another words, Olivier (and 
you) didn't bother to google out articles
>>>>>> on that and thought he was the 
smartest guy.
>>>>> yeah. That time there was a LOT of other stuff to bother 
about, than
>>>>> colliders :) Paint me ashamed ;>
>>> I am not saying you are 
to be blamed, but Frederic, as supervisor of the
>>> project, should have 
managed that.
>> I recall his point of view: SDEC has a lot slower collider 
>> it was "check everything with everything"?. Some SDEC user could tell

>> us). And so Frederic was very happy to see how much faster SAP is :)

>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

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