[mechem]

Hi Foamers,

Which collision model is used in MPPICFoam that is introduced in the new version of OpenFOAM? http://www.openfoam.org/version2.3.0/dpm.php

Is it soft sphere model or hard sphere model?

Regards,

[maysmech]

Originally Posted by mechem

Hi Foamers,

Which collision model is used in MPPICFoam that is introduced in the new version of OpenFOAM? http://www.openfoam.org/version2.3.0/dpm.php

Is it soft sphere model or hard sphere model?

Regards,

Good question!
It seems a good solver in Lagrangian modeling of dense systems.
I searched about this solver but didn't found any references about it.
I will try to read and understand source files.

If anyone knows about MPPICFoam please share here.

[wyldckat]

Greetings to all!

I was curious and managed to look into this sooner. Here are the following reasons why I think that OpenFOAM only has hard sphere models:

1. Search for "variable hard sphere collision model" in the release notes for OpenFOAM 1.6: http://www.openfoam.org/archive/1.6/...ease-notes.php
2. If you search in the OpenFOAM source code for "softImpact":
   

   find $FOAM_SRC -name "*.H" -type f | xargs grep "softImpact"

   You'll find only one file, namely "src/lagrangian/basic/particle/particle.H", where it shows this:
   

               //- Return the impact model to be used, soft or hard (default).            inline bool softImpact() const;

   It's not a virtual method and it's hard-coded in the file "src/lagrangian/basic/particle/particleI.H" to be "false".
   This means that there is no particle model implemented in OpenFOAM for soft impact.

Best regards,
Bruno

[mechem]

Thanks a lot Bruno and Maysam,
If it is hard sphere model, Is it same as conventional hard sphere model with parameters like normal restitution (e_n), Tangential restitution (Beta_0) and dynamic friction (miu_f)?
Using particles "cloud" is vague. What is the function of cloud in this new solver, I didn't understand the text in the release note:

The functionality is implemented into a new MPPIC particle cloud which is used in the new MPPICFoam solver (which is identical to DPMFoam, except it used a colliding particle cloud). Particle-particle interactions are represented by models which utilise mean values calculated on the Eulerian mesh.

Does this solver use cloud or solve each particle collision? and If it uses cloud how is the mechanism of collision? If it doesn't use cloud why is it use cloud solvers?

Regards,

[Cyp]

Dear all,

I glad you speak up about this DEM feature of OpenFOAM.

I am still very confused about the difference between DPMFoam and MPPICFoam...

Let's say I want to simulate the dynamic of a granular medium which of the two solvers should I use?

[wyldckat]

Greetings to all!

Answering in order of the questions made... and please keep in mind that I'm not an authority on this topic, I just know a few details in OpenFOAM that might help you get a better grasp to what things mean and how I interpreted them.

Originally Posted by mechem

If it is hard sphere model, Is it same as conventional hard sphere model with parameters like normal restitution (e_n), Tangential restitution (Beta_0) and dynamic friction (miu_f)?

I don't know. All I know is that they specifically state:

Originally Posted by http://www.openfoam.org/version2.3.0/dpm.php

This version includes an implementation of the Multiphase Particle-in-Cell (MP-PIC) method for collisional exchange, according to P. J. O’Rourke et al., Chemical Engineering Science 64:1784-1797, 2009.

If you carefully read the features page and what I've written below, you might also reach the conclusion that it's more likely that DPMFoam is the one that more strictly abides to those parameters, but on the other hand it seems that MPPICFoam has options for also taking those details into account or to model those details in another form.

Originally Posted by mechem

Using particles "cloud" is vague.

It's how the particles are managed. AFAIK, "Cloud" in OpenFOAM is analogous to the mesh:

• The fluid/energy flows inside the mesh. It's as the mesh is what helps us manage the simulation of the fluid flow.
• The "cloud" is the overall presence of all particles, whether they're active or not. It's what helps us manage the simulation of the particle flow.

The last few questions relate essentially to the same question. Let's see if I'm able to break down what's explained in the official page and from the source code descriptions: http://www.openfoam.org/version2.3.0/dpm.php

• DPMFoam will calculate particle-particle interactions, using the existing cloud management system. Then it passes the information into the fluid as if it were oil on water. Quoting from the description at "$FOAM_SOLVERS/lagrangian/DPMFoam":
  

  Transient solver for the coupled transport of a single kinematic particle cloud including the effect of the volume fraction of particles on the continuous phase.

• MPPICFoam ... uhm, I had to look into the comment section of the file "$FOAM_SOLVERS/lagrangian/DPMFoam/MPPICFoam/MPPICFoam.C", which has an almost identical description, except it also states this afterwards:
  

  Multi-Phase Particle In Cell (MPPIC) modeling is used to represent collisions without resolving particle-particle interactions.

  In other words, acts almost like DPMFoam, but it uses another methodology for how the particles interact in the cloud of particles, with additional options, as described in the feature page.

Originally Posted by Cyp

Let's say I want to simulate the dynamic of a granular medium which of the two solvers should I use?

Uhm... same as with any other solver? Find one or more validation cases that is/are similar to your case and simulate with both solvers, to see which one gives a better result for your specific simulation!?
Or simply compare the two solvers with the "Goldschmidt" case, which seems to be the validation case used.

Best regards,
Bruno

[maysmech]

DPM handles particle-particle collision in a very distinctive manner. It uses the projection of the volume fraction unto the Eulerian mesh to calculate a "granular pressure" that is used as an isotropic stress tensor. The gradient of this granular pressure is then used as a source term in the motion of the particle. It usually leads to a stiff pressure and etc., so it's not as trivial as it sounds.
There is a very good article (Snider-2001) on that method in 3d : http://www.sciencedirect.com/science...21999101967476
Cheers,
Bruno

Based on this comment which I copied from another forum (Bruno is name similaity with our Bruno, I think) I have some problems with dpm in OpenFOAM:
If I understand correctly from paper of (Sinder,2001), DPM in OpenFOAM doesn't use hard sphere or soft sphere models and defines granular pressure and temperature like TFM. Isn't it?
If yes, is it an euler-euler or euler-lagrange approach? As I know DPM or DEM should solve Newton's law for discrete phase but why didn't it any Newton's law in this paper?
Are DPMFoam an MPPICFoam use same routine? The paper talks about MP-PIC in whole of its text. In OpenFOAM 2.3.0 release note, it is stated that both of them are same except colliding. I didn't find any reference about dpmFOAM collision manner.

This version includes an implementation of the Multiphase Particle-in-Cell (MP-PIC) method for collisional exchange, according to P. J. O’Rourke et al., Chemical Engineering Science 64:1784-1797, 2009. The functionality is implemented into a new MPPIC particle cloud which is used in the new MPPICFoam solver (which is identical to DPMFoam, except it used a colliding particle cloud). Particle-particle interactions are represented by models which utilise mean values calculated on the Eulerian mesh.

Thanks

[Fransje]

Hello Maysmech,

I was wondering if you had made any progress in your investigation of DPMFoam and MPPICFoam.

Kind regards,

Francois.

[sophie_l]

Hey guys,

I'm curious about MPPICFoam as well. Just wondering do you know how to implement periodic boundary conditions for the particles please? Is there patch functions available currently or do I have to write my own code to realize it? Could you have a look at my post here for more details of my question please?http://www.cfd-online.com/Forums/ope...particles.html Thank you.

Sophie

[ali_atrian]

thanx for the reference

[minzhang]

Originally Posted by maysmech

Good question!
It seems a good solver in Lagrangian modeling of dense systems.
I searched about this solver but didn't found any references about it.
I will try to read and understand source files.

If anyone knows about MPPICFoam please share here.

Hello maysmech,

I am wondering how is your exploration of MPPICFoam/DPMFoam going?

I am a Ph.D. student in Petroleum Engineering.
I have been working on MPPICFoam during the past 3 months.
My focus is to apply MPPICFoam to simulate proppant/particle transport in the wellbore (a cylinder), through a perforation (it is a constricted geometry compared with a wellbore), and fractures.

Now, I have a tough problem.
Our simulation case has a wide solid volume fraction range (from assumed even spatial distribution near the inlet, which can be 0-20%, to dense flow near the perforation (the constricted area), which can be 40-60+%).
Then, I find that it is very difficult for MPPICFoam to handle this situation.
The error message is, the max. particle volume fraction is larger than 1 and then it crashes.

Any comments and suggestions would be very very appreciated!

Thanks and best regards,
Min

[minzhang]

Originally Posted by Cyp

Dear all,

I glad you speak up about this DEM feature of OpenFOAM.

I am still very confused about the difference between DPMFoam and MPPICFoam...

Let's say I want to simulate the dynamic of a granular medium which of the two solvers should I use?

Hello,

I am wondering whether you have a better understanding of MPPICFoam and DPMFoam now.

If we set nParticle=1 for DPMFoam, what is the difference between unresolved CFD-DEM and DPMFoam?

If we set nParticle>1 for DPMFoam, what is the difference between coarse-grained CFD-DEM and DPMFoam?

Thank you so much!

[minzhang]

Originally Posted by wyldckat

It's how the particles are managed. AFAIK, "Cloud" in OpenFOAM is analogous to the mesh:

• The fluid/energy flows inside the mesh. It's as the mesh is what helps us manage the simulation of the fluid flow.
• The "cloud" is the overall presence of all particles, whether they're active or not. It's what helps us manage the simulation of the particle flow.

I still cannot understand the concept of cloud very well. All the particles belong to a cloud, yes? What is the function of Cloud?

[minzhang]

Hello All,

Could you have a look at my post?
Simulate particle/liquid flow in a converging geometry with MPPICFoam

Thanks and best regards,
Min