what causes an agglomerate to fragment?

Fatemeh Hosseini_22198
Fatemeh Hosseini_22198 Altair Community Member
edited October 2023 in Community Q&A

Hello everyone,
In the CFD-DEM simulation, I had a big agglomerate containing 900 primary particles.
During the simulation, it breaks into two different agglomerates with 400 and 500 primary particles.
I know turbulence shear or colliding with other agglomerates/geometry may cause this fragmentation but I couldn't find any criteria in EDEM documents or help.
Does it depend on impact velocity or kinetic energy of collision?
if yes, where can I find these equations or formulas in EDEM documents?

Regards,
Fatemeh



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Answers

  • Stefan Pantaleev_21979
    Stefan Pantaleev_21979
    Altair Employee
    edited September 2023

    Hi Fatemeh,

    Particles in the agglomerate will separate if the forces trying to separate them are greater than the forces keeping them together.

    The forces that separate particles could result from collisions and fluid drag forces among others.

    The forces keeping particles together depend on the contact model and could be van der Waals type forces (JKR model, EEPA model) and solid bridge forces (bond model) among others.The magnitude of these forces depends on the respective model parameters (surface energy for JKR model, surface energy and pull-off force for EEPA model and bond critical shear and normal stress for the bond model). You could generally have anything from weak and brittle agglomerates to complete;y unbreakable agglomerates depending on the contact model and its parameters.

    JKR model: https://help.altair.com/edem/Creator/Physics/Base_Models/Hertz-Mindlin_with_JKR.htm

    EEPA model: https://help.altair.com/edem/Creator/Physics/Base_Models/Edinburgh_Elasto-Plastic_Adhesion_Model_(EEPA).htm

    Bond model: https://help.altair.com/edem/Creator/Physics/Additional_Models/Bonding_V2.htm

    Best regards,

    Stefan

     

  • Fatemeh Hosseini_22198
    Fatemeh Hosseini_22198 Altair Community Member
    edited October 2023
    Stefan Pantaleev_21979 said:

    Hi Fatemeh,

    Particles in the agglomerate will separate if the forces trying to separate them are greater than the forces keeping them together.

    The forces that separate particles could result from collisions and fluid drag forces among others.

    The forces keeping particles together depend on the contact model and could be van der Waals type forces (JKR model, EEPA model) and solid bridge forces (bond model) among others.The magnitude of these forces depends on the respective model parameters (surface energy for JKR model, surface energy and pull-off force for EEPA model and bond critical shear and normal stress for the bond model). You could generally have anything from weak and brittle agglomerates to complete;y unbreakable agglomerates depending on the contact model and its parameters.

    JKR model: https://help.altair.com/edem/Creator/Physics/Base_Models/Hertz-Mindlin_with_JKR.htm

    EEPA model: https://help.altair.com/edem/Creator/Physics/Base_Models/Edinburgh_Elasto-Plastic_Adhesion_Model_(EEPA).htm

    Bond model: https://help.altair.com/edem/Creator/Physics/Additional_Models/Bonding_V2.htm

    Best regards,

    Stefan

     

    Hi Stefan,
    Many thanks for your answer. 
    I used JKR for the contact model and I see breakage of large agglomerates in the simulation. 
    I need equations about this process(sth like the balance between forces that you mentioned) for my article but I couldn't find anything in EDEM help.
    Is there any section about agglomeration and fragmentation in EDEM documents?


    Regards,
    Fatemeh

  • Stefan Pantaleev_21979
    Stefan Pantaleev_21979
    Altair Employee
    edited October 2023
    Fatemeh Hosseini_22198 said:

    Hi Stefan,
    Many thanks for your answer. 
    I used JKR for the contact model and I see breakage of large agglomerates in the simulation. 
    I need equations about this process(sth like the balance between forces that you mentioned) for my article but I couldn't find anything in EDEM help.
    Is there any section about agglomeration and fragmentation in EDEM documents?


    Regards,
    Fatemeh

    Hi Fatemeh,

    Please see the equations for JKR v2 model in the EDEM documentation:

    JKR v2 documentation

    The particles will separate when the forces pulling the particles apart exceed F_nc

    For further details please see:

    Thornton C. (2015) Granular Dynamics, Contact Mechanics and Particle System Simulations: A DEM Study. Vol. 24. Springer.

    Best regards,

    Stefan

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