Why do particle jump during CFD-DEM simulation?

Updated Jun 16, 2023 by Fatemeh Hosseini_22198

Hello, everybody,

I noticed particles jumping from the bottom of the tube during the CFD-DEM simulation (in a horizontal tube with gravity in the Z direction).
Since I have gravity in my system, they should move on the lower part of the tube. (Please refer to the attached)
I ran this simulation in a larger tube, and I didn't observe any strange behavior. Do you believe dp/D may be causing the problem? (D is the tube diameter, and dp is the particle diameter).
Currently, the D/dp is 200, whereas it was 1000 in the previous instance.
Or do you think the P-W surface energy is the cause of it?

I appreciate your assistance in advance.

Regards,
Fatemeh

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PrasadAvilala

Altair Employee

Updated Jun 12, 2023 by PrasadAvilala

Hi Fatemeh,

The only reason I feel is the time step either in EDEM or CFD is larger.

You can try to reduce the time step in EDEM to lower until you get stable behavior or you can retain the current time step as it is in EDEM and reduce in CFD.

either way, it works.

Thanks,

Prasad A

Altair Community Member

Updated Jun 12, 2023 by Fatemeh Hosseini_22198

Hi Fatemeh,

The only reason I feel is the time step either in EDEM or CFD is larger.

You can try to reduce the time step in EDEM to lower until you get stable behavior or you can retain the current time step as it is in EDEM and reduce in CFD.

either way, it works.

Thanks,

Prasad A

Thanks for your answer, Prasad.

In the last simulation CFD/DEM time step =50 and now it is 20.
EDEM timestep is 20% Rayleigh too.

Particles velocity is in the range of Fluid velocity and I think now it is stable.

Regards,
Fatemeh

PrasadAvilala

Altair Employee

Updated Jun 12, 2023 by PrasadAvilala

yes, hopefully, but you have to check and reduce until stable flow occurs.

Thanks,

Prasad A

Altair Community Member

Updated Jun 13, 2023 by Fatemeh Hosseini_22198

yes, hopefully, but you have to check and reduce until stable flow occurs.

Thanks,

Prasad A

Dear Prasad,
I reduced the time step in the DEM section from 20% of Reyleigh to 15%, but nothing changed.
I also lowered the CFD time step, but the procedure wasn't made better. I still have the particles that jump.
I think it might be due to the D/dp or p-w surface energy.

Regards,
Fatemeh

PrasadAvilala

Altair Employee

Updated Jun 13, 2023 by PrasadAvilala

Dear Prasad,
I reduced the time step in the DEM section from 20% of Reyleigh to 15%, but nothing changed.
I also lowered the CFD time step, but the procedure wasn't made better. I still have the particles that jump.
I think it might be due to the D/dp or p-w surface energy.

Regards,
Fatemeh

Hi Fatemeh,

are you using HWCFD (Acusolve)?

if yes, you can share the files let me take about the factory definition along with time step.

Thanks,

Prasad A

Altair Community Member

Updated Jun 13, 2023 by Fatemeh Hosseini_22198

Hi Fatemeh,

are you using HWCFD (Acusolve)?

if yes, you can share the files let me take about the factory definition along with time step.

Thanks,

Prasad A

Thanks a lot
The file has been sent to your email.

Regards,
Fatemeh

Altair Community Member

Updated Jun 13, 2023 by Fatemeh Hosseini_22198

@Stephen Cole, May I have your opinion too?

Thanks in advance.

Regards,
Fatemeh

Mahdi_22303

Altair Community Member

Jun 15, 2023

Updated Jun 15, 2023 by Mahdi_22303

Is it possible that although you have reduced the size of the tube, you have increased the flow velocity to maintain a fixed discharge in the tube? Then, it is possible that sediment particles settle and then entrain into the flow by some sweeping and ejection motions. It might be a hydrodynamic reason.