Interaction between the particles in a clump

Asked by Yuxuan Wen on 2020-11-20

Hello,

I am interested at whether there is interaction between the particles in a clump. So I searched the questions and found one with the clarification that there is no interaction between the particles in a clump, see below:
https://answers.launchpad.net/yade/+question/403339

In this question, Mr. Jérôme Duriez answered with a example code:
******** Example **********
O.bodies.append(sphere(Vector3(0,0,0),1,fixed='True'))
O.bodies.append(sphere(Vector3(0,0,1.99),1,fixed='True'))
O.bodies.clump([0,1])
O.step()
O.interactions.has(0,1) # returns false here (true without O.bodies.clump() line)
***************************

He said that the example code will give a "False" at the end. However, I tried his example code and found that the result is "True". I tried many other times and found that there is interaction between the particles in a clump.

I am thinking that, if the bodies are generated by "O.bodies.append()" and are in contact with each other, even we clump them in the next step, the interactions between these bodies will not be removed, instead, these interactions will be in a constant state. Am I thinking correctly? I will be much appreciated if anyone could help me, thank you!

Regards,
Yuxuan Wen

Question information

Language:
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Status:
Solved
For:
Yade Edit question
Assignee:
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Solved by:
Jan Stránský
Solved:
2020-11-21
Last query:
2020-11-21
Last reply:
2020-11-20

This question was reopened

Jan Stránský (honzik) said : #1

Hello,

> I tried his example
> the interactions between these bodies will not be removed

what is "his example"? The code in OP? If yes, then there are no "interactions between these bodies" (they are clumped before O.step)

cheers
Jan

Yuxuan Wen (wenyuxuan) said : #2

Hello Jan, thank you for your reply!

The example code is in the OP:

******** Example **********
O.bodies.append(sphere(Vector3(0,0,0),1,fixed='True'))
O.bodies.append(sphere(Vector3(0,0,1.99),1,fixed='True'))
O.bodies.clump([0,1])
O.step()
O.interactions.has(0,1) # returns false here (true without O.bodies.clump() line)
***************************

I run this example, If there is no interactions, the result should return "False" for "O.interactions.has(0,1)". However,I run it in YADE and it return "True", which makes me so confused.

As you said, they are clumped before the O.step(), so there should be no interaction. I run the code line by line in the terminal, do you think it affect the result?

Regards,
Yuxuan

Jan Stránský (honzik) said : #3

Thanks for clarification.

Normally it should work like you described:
- new interactions are not created within a clump
- existing interactions are not deleted (if a clump is made of interacting particles)

I am not sure with the second point, but looks like that from quick simple tests (e.g. switching O.bodies.clump and O.step in the example code)

Why it is not like that in your code might have several reasons:
- do you run in "clean" terminal? Can you try using a script file?
- what version of Yade do you use?

cheers
Jan

Yuxuan Wen (wenyuxuan) said : #4

Hello Jan, thank you for your answer!

- do you run in "clean" terminal? Can you try using a script file?

Yes, now I run the code both in the "clean" terminal and through a script file. Both shows "True" for "O.interactions.has(0,1)", which means that there is interaction between the two sphere bodies. In the code, the O.bodies.clump() is run before the O.step(), so according to your clarification there should be no interaction. The contraction makes me so confused, is these results consistent in your computer?

 - what version of Yade do you use?

I use Yade 2018.02b, do you think this version works?

Kind Regards,
Yuxuan Wen

Best Jan Stránský (honzik) said : #5

> I use Yade 2018.02b, do you think this version works?

thanks for information. Definitely it has influence. For me:
Yade 2020-06-23.git-f03a37c: False
Yade 2018.02b: True

cheers
Jan

Yuxuan Wen (wenyuxuan) said : #6

Hello Jan,

Thank you for your answer! It really helps! I think I need to update the YADE to the latest version.

Kind Regards,
Yuxuan

Yuxuan Wen (wenyuxuan) said : #7

Thanks Jan Stránský, that solved my question.

Jan Stránský (honzik) said : #8

Using yadedaily is the easiest way IMO, see https://yade-dem.org/doc/installation.html
cheers
Jan

Yuxuan Wen (wenyuxuan) said : #9

Got it!! Thank you Jan and have a nice weekend!!
Yuxuan Wen