Weird behavior of particles.

Fatemeh Hosseini_22198
Fatemeh Hosseini_22198 Altair Community Member
edited November 2022 in Community Q&A

Hello every body,
I am simulating Fluent-EDEM coupling.(Particles flow in a turbulent flow with HM-JKR contact model between particles and tube)
I saw weird movement in the particles.
There is a horizontal tube with gravity . In some specific part of the tube particles escape from the wall!
Logically they should settle down a bit, based on the gravity but they don't.
I choose all the parameter from literature.
Could you please guide me what may cause this problem?
(The flow direction is y and gravity is on the -Z direction).
Please see the screen shot of the particles (which is the inlet of the tube).

Regards,
Fatemeh

 

 

image

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Answers

  • Stephen Cole
    Stephen Cole
    Altair Employee
    edited November 2022

    Hi Fatemeh,

     

    I would first recommend checking if the simulation is stable with EDEM alone with the set parameters and time-step  The material should settle if there are no external forces and you can plot the kinetic energy over time to confirm this.

    Otherwise I'd check the time-step in Fluent and the time-step Ratio.  With regard to the ratio between EDEM and Fluent this is typically in the range of 10:1 or 100:1 (EDEM time-step lower) however reducing the ratio improves stability.  

    On a separate note the time-step in your image does look very low, we do typically run around 20% of Rayleigh time-step however the value of 3e-10 s is low. This maybe OK depending on the case however i'd expect it takes a long time to run.  There are ways of improving simulation speed for example - https://community.altair.com/community?id=community_blog&sys_id=593445c11b2f6810c4dfdbd9dc4bcb06

     

    Regards
    Stephen

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