Learning Forum

[kiran.purushothamakeshavan]

Hello,

I'm getting this error for a simple case of DDPM injection, the domain is a cube where the particles are just falling on a surface.

Writing to DESKTOP-70DFQ0F:"C:\Users\Naseeb\OneDrive - Ontario Tech University\Desktop\Fluent\Granular accumulation 2\granular_files\dp0\FFF\Fluent\FFF-14-00000.dat.h5" in NODE0 mode and compression level 1 ...

Writing results.

Writing particle data.

Done.

 

 

DPM Iteration ....

 

Updating solution at time levels N and N-1.

done.

Injecting 144 particle parcels with mass 1e-07 at t = 0

number tracked = 144

 

iter continuity u-phase-1 v-phase-1 w-phase-1 energy-p1 time/iter

1 1.0000e+00 0.0000e+00 5.4530e-10 0.0000e+00 0.0000e+00 0:00:12 39

! 1 solution is converged

 

Advancing DPM injections ....

number tracked = 144

Flow time = 0.001s, time step = 1

999 more time steps

 

DPM Iteration ....

 

Updating solution at time levels N and N-1.

done.

Injecting 144 particle parcels with mass 1e-07 at t = 0.001

number tracked = 288

 

iter continuity u-phase-1 v-phase-1 w-phase-1 energy-p1 time/iter

1 1.0000e+00 0.0000e+00 5.4530e-10 0.0000e+00 0.0000e+00 0:00:12 40

Stabilizing mp-x-momentum to enhance linear solver robustness.

Stabilizing mp-x-momentum using GMRES to enhance linear solver robustness.

Stabilizing mp-y-momentum to enhance linear solver robustness.

Stabilizing mp-y-momentum using GMRES to enhance linear solver robustness.

Stabilizing mp-z-momentum to enhance linear solver robustness.

Stabilizing mp-z-momentum using GMRES to enhance linear solver robustness.

Stabilizing pressure correction to enhance linear solver robustness.

Stabilizing pressure correction using GMRES to enhance linear solver robustness.

 

Divergence detected in AMG solver: pressure correction Stabilizing temperature to enhance linear solver robustness.

Stabilizing temperature using GMRES to enhance linear solver robustness.

temperature limited to 1.000000e+00 in 1728 cells on zone 2 in domain 2

temperature limited to 1.000000e+00 in 1728 cells on zone 2 in domain 3

 

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: pressure correction

Error at host: floating point exception

 

===============Message from the Cortex Process================================

 

Compute processes interrupted. Processing can be resumed.

 

==============================================================================

 

Error at Node 7: floating point exception

 

Error at Node 23: floating point exception

 

Error at Node 26: floating point exception

 

Error at Node 28: floating point exception

 

Error at Node 25: floating point exception

 

Error at Node 22: floating point exception

 

Error at Node 13: floating point exception

 

Error at Node 11: floating point exception

 

Error at Node 9: floating point exception

 

Error at Node 24: floating point exception

 

Error at Node 10: floating point exception

 

Error at Node 4: floating point exception

 

Error at Node 16: floating point exception

 

Error at Node 20: floating point exception

 

Error at Node 18: floating point exception

 

Error at Node 15: floating point exception

 

Error at Node 14: floating point exception

 

Error at Node 0: floating point exception

 

Error at Node 29: floating point exception

 

Error at Node 27: floating point exception

 

Error at Node 8: floating point exception

 

Error at Node 19: floating point exception

 

Error at Node 1: floating point exception

 

Error at Node 5: floating point exception

 

Error at Node 12: floating point exception

 

Error at Node 6: floating point exception

 

Error at Node 21: floating point exception

 

Error at Node 17: floating point exception

 

Error at Node 2: floating point exception

 

Error at Node 3: floating point exception

 

Error: floating point exception

Error Object: #f

Writing "| gzip -2cf > SolutionMonitor.gz"...

Writing temporary file C:\Users\Naseeb\AppData\Local\Temp\flntgz-1218017 ...

Done.

 

 

Calculation complete.

 

[Rob]

There's no carrier phase flow by the looks of it so the mass fraction may be a little high. What are you modelling?

[kiran.purushothamakeshavan]

Hi,

I'm just trying to see an accumulation of particles on a flat surface, I changed the mass flow rate and als under relaxed the mass flow rate parameter, still the same results

[Rob]

Accumulation as in height or just a number value of build up? The latter could be done using the DPM accretion model. For a full accumulation including angle of repose you may need to consider Rocky. 

[kiran.purushothamakeshavan]

Using the granular DDPM, I was able to simulate a fluidised bed on fluent, so I tried using injections instead of physically defining the particles in a region.
Here there is a distinction between fluid and granular matter just as seen in a DEM code. Why does injections not seem to work? The particles seem to coincide with each other if we try to do this on DDPM injection.

Also where can I find tutorials which couple fluent and rocky? I understand rocky has been with ansys in recent times but are there resources which specifically talk about CFD-DEM coupling?

[Rob]

There are some materials in Learning on here for Fluent & Rocky. 

DDPM extends DPM into higher volume fractions using the Eulerian model. It's a good model, but I'd not recommend it's use for fluidised beds or where you expect larger regions with higher volume fractions. 

[kiran.purushothamakeshavan]

Also, I do not want to use this for high-volume fractions, I just want to assess the particle accumulation on flat surfaces using a DDPM approach, I know it's possible but I see the same error as shown above when I release particles from an inlet at a height 'h' made to fall on a flat surface.

I followed the method described here 
In a thesis titled 'CFD SIMULATION OF SEDIMENTATION OF SMALL PARTICLES' from Czech Technical University, details how we can get an accumulation of granular particles using DDPM. The problem arises when I change the particle inlet from the frontal 2D mesh surface (surface_body) to the top inlet of the rectangular 2D domain.

I keep getting a similar error as shown above, could you possibly help me understand why this could happen?

 

[kiran.purushothamakeshavan]

Thanks!
Are there tutorials where DDPM particles from injections accumulate on surfaces?

All literature online talk about mesh deformtion to show accumulation, like you mentioned some show particle accumulation as a contour but none as a particle on particle 3D accumulation as seen in ROCKY

[Rob]

I'm not aware of DDPM tutorials for accumulation, the model will try and revert to the granular phase model, rather than build up. Hence suggesting Rocky if there is a lot of deposition. 

The floating point could mean your time step is too high, but may also be linked to the way DDPM tries to maintain the volume fraction. Free falling particles are always problematic when released from rest as the next release invariably overlaps the previous particles whilst the time step is linked to the fastest moving part of the domain. 

[kiran.purushothamakeshavan]

I have run a few cases to observe the accumulation, I see a pattern but I need you to please help me come to a conclusion.
I find that the particle volume fraction contour shows accumulation as a function of time. But when I monitor the particle tracks for particle residence time, the particles seem to overlap. My question is if particle tracks on Fluent has the capability to show layer over layer accumulation similar to the soft-sphere approach in Rocky.

Please comment.

[Rob]

Which comes back to how the DPM model works. There's a reason I mentioned Rocky.