Hello all,
I am trying to grow particles in a certain region upto a certain size in liggghts with CFDEM coupling. I want to try this because inserting particles as a stream with their final diameter seems to cause spikes in the CFD calculations.
I can do this easily with only liggghts. However in CFDEM, I am having the problem of reassigning the group everytime new particles are inserted in the region or stop growing once the particles have reached their final diameter.
group new_insert region insert
Is there a way make an if statement or this group statement be evaluated every N time steps? Any help will be very useful. I have attached my liggghts code if anyone would like to take a look.
Cheers
Som
P.S.: Also, I have noticed that inserting a stream of particles in the unresolved case works, but the resolved cases always crash as soon as the new particles are created (both with static or dynamic meshes). Has anyone had any experiences with that?
| Attachment | Size |
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 in.liggghts_resume_coupled_grow.txt | 4.12 KB |
cgoniva | Thu, 02/07/2013 - 17:37
Hi,
Hi,
the problem stems from the volume, which you generate when inserting the particles (acts like an explosion ;)
can you insert the particles outside the CFD domain ans they move into it with time?
otherwise you will have to make sure that d(voidfraction)/dt is ignored whenever you insert particles - (coding necessary).
Cheers,
Chris
Maryam | Sat, 04/13/2013 - 03:58
Where to change the code?
Hi Chris,
Could you kindly let us know where to change the code to ignore the sudden change in the void fraction? I tried inserting particles out of the CFD domain and let them move into the domain, but it did not help.
Thank you
cgoniva | Wed, 04/17/2013 - 15:01
Hi,
Hi,
did you already update to the latest version - there was an issue with exactly that topic (ddt(voidfraction)) ?
Cheers,
Chris
Maryam | Wed, 04/17/2013 - 22:29
Thanks, I had narrowly missed
Thanks, I had narrowly missed that last version.
I tested it. Although the domain of fluctuations is much smaller in this version, it still gives non-physical values such as negative values. For instance, in the case that I am running right now, inlet pressure varies between -600 and 600!
Somnath | Tue, 02/12/2013 - 04:34
Hi,
Hi,
Yes, that is exactly what I ended up doing: creating the particles outside and then flowing them in to the domain (btw, insert/rate/region seems to work best for this as compared to insert/pack or insert/stream).
I had realised that the sudden creation of particles was causing the simulation to explode :) That is why, I was trying to grow the particles from very small volumes. However, I am still curious to know if it is possible to grow or shrink the particles in a certain region in cfdem? As I said before, the problem seems to be that I am not being able to update the particles present in a region to a group every N steps (through a loop or something).
Thanks
Som
cgoniva | Thu, 02/21/2013 - 09:16
Hi Som,
Hi Som,
for executing LIGGGHTS commands during a coupled run, I generated the liggghtsCommand models. The "execute" command model can be used in a modular way to run certain commands during run time.
Cheers,
Chris