Reduction of particle diameter over time ?

Submitted by xinze_l on Sat, 10/23/2010 - 05:39

Hello Christoph,

I wonder which commands can complete the reduction of particle diameter over time in a specified region just as you have gived example lammps_particleReduction_.wmv in this web. I think it is maybe lammps's some command or tips, Could you kindly give me help or instruction?

Thank you.

best regards,

leexz

Forums:

xinze | Sun, 10/24/2010 - 14:46

Thank you, Christoph!
I will try it soon.
best,
xinze

ckloss's picture

ckloss | Sun, 10/24/2010 - 15:23

typo: I meant packing "example", not "command"

Christoph

xinze_l | Tue, 10/26/2010 - 05:54

Hello, Christoph

I understand the means, I read the packing example, but I have two question:

question 1:

region top block -1.8 -1.0 -0.3 0.0 0.75 1.35 units box
group top region top

How can I make particles to move into region "top" belong to group "top" at every timestep with time elapsing. As you known, in liggghts if only using the above command, particles belong to group "top" do not change with run, even if new particle enter into region "top", it not either update the group's information.

question 2:

which commands may carry out deleting particle in specified region if particle radius chang into below some size when simulation are running. The most important thing is how to specify the conditions.

In addition, if you are freedom and kind to me, whether may you share your script of example "Reduction of particle diameter over time" with me. please email to me, Thank you.

best,
xinze

raguelmoon's picture

raguelmoon | Tue, 10/26/2010 - 06:42

Hi xinze,
what do you want to do? your question is not clear. I guess you want to move the cluster of particles in the region. Please use different names for region ID and group ID. If you want to move the particles you have inserted in the region then group the particles by their type, for example:
group topparticles type 1

There is no script "Reduction of particles diameter over time". You have to change the script "packing" in example folder by yourself. Just read carefully about fix adapt command in doc page.

Best,
Ram

Ram

xinze_l | Tue, 10/26/2010 - 10:59

region A
group Ag region A
fix reduce Ag adapt 1 atom diameter size

At beginning of simulation, simulation box was filled by many particles, regrion A inside of the box. and using the above command particles in region A belong to group Ag. But when particles in group Ag was redued at next timestep, particles above region A will flow into region A. while the new particles into region A will be not reduced because they not belong to group A. Do you understand me?

best,
xinze

ckloss's picture

ckloss | Tue, 10/26/2010 - 13:58

you could periodically issue delete group Ag and re-assign it with the every keyword of the runn command

Christoph

xinze_l | Tue, 10/26/2010 - 15:42

Thank you Christoph, it works fine.

Another question:
If diameter of particles reduce < 0.001 in group Ag after some timestep, the particles will remove from the simulation. how achieve this object. what tips, thank you.

best,
xinze

ckloss's picture

ckloss | Tue, 10/26/2010 - 16:09

as written above:

>>which commands may carry out deleting particle in specified region if particle radius chang into below
>> some size when simulation are running
This is not out of the box, you would have to write your own "fix" command for that (which would not be too difficult)

Christoph

xinze_l | Tue, 10/26/2010 - 16:33

Thanks Christoph quickly answer!

Could you give me some advice about reading which some piece codes in LIGGGHT for quickly implementing this fix command.

I really appreciate your help!
thank you!

By the way, I kown you have released the CFD-DEM code through git. Thank you, I will play with it as soon as possible. Thanks for your remarkable contribution to DEM community.

Best regard,
xinze

xinze_l | Tue, 10/26/2010 - 18:16

OK，Thanks Christoph！

I have managed to implement the function I want. Thank you very much.

regard,
xinze

xinze_l | Wed, 10/27/2010 - 17:35

In a simulation, whether "fix adapt" command may use twice? Today I change the script for two group particles using "fix 1 group1 adapt 1 atom diameter size1" then another "fix 2 group2 adapt 1 atom diameter size2", then Liggghts broken. why? please give me some suggestion, thank you.

best,
xinze

ckloss's picture

ckloss | Wed, 10/27/2010 - 18:09

yes, currently it's restricted to one - I would be quite easy to change that, but simple no one has done that yet - feel free to try

Christoph

xinze_l | Wed, 10/27/2010 - 18:27

would you give me some advise? I will try to improve it. which variable control this, or give me some hints. Thanks

best,
xinze

xinze_l | Thu, 10/28/2010 - 13:55

Hello, Christoph
I have manage to implement it in the fix_adapt.h and fix_adapt.cpp.
I have added the a private variable “char *adaptname” into adapt.h and use "adaptname" replace hard-coded string "adaptProp" in adapt.cpp, now it work fine. I wonder whether we employ the same approach for resolving this problem.

best,
xinze

ckloss's picture

ckloss | Thu, 10/28/2010 - 13:58

>>I wonder whether we employ the same approach for resolving this problem.
Which problem? The files i sent you _do_ resolve the problem, dont they?

Anyway, I will leave this specific issue now to you.

Cheers,
Christoph

xinze_l | Thu, 10/28/2010 - 14:59

Sorry, I do not timely catch sight of letter you sent to me with the revised adapt.h(cpp) files, because my gmail made your letter migrate the spam folder. Now i got them.

Because I don't known you have sent a letter to me, today I spent a day for resovling this problem. I will sent my solution to you. Essentially, both of us adapted the same method.

Thank you!

Cheers,
xinze

ckloss's picture

ckloss | Tue, 10/26/2010 - 14:00

>>How can I make particles to move into region "top" belong to group "top" at every timestep with time elapsing.
See below, periodically delete the group and re-define it based on the region would solve the problem

>>which commands may carry out deleting particle in specified region if particle radius chang into below
>> some size when simulation are running
This is not out of the box, you would have to write your own "fix" command for that (which would not be too difficult)

Christoph