Issue with producing output vtk file for gas volume fraction, pressure and velocity vectors

[sayyamchopra]

HI, I AM WORKING ON CHEMICAL LOOPING DESIGN USING DEM MODELLING. I AM TRYING TO GENERATE OUTPUT RESULTS FOR VOLUME FRACTION, PRESSURE AND VELOCITY VECTORS FOR GAS, BUT THE SYSTEM ISN’T GENERATING THE FILES AND THE VTK FILES IS NOT RUNNING FOR THE PARAMETER DEFINED.IT IS STATIONARY. ALSO, THE BED WHICH I HAVE PATCHED FOR THE PARTICLES IN THE SYSTEM ISN’T CLEAR AT ALL. IT HAS FLAKY PATCHES AND IS NOT COVERING THE WHOLE GEOMETRY.

ISSUE WITH THE SYSTEM:

1. NOT GENERATING VELOCITY VECTORS.
2. NOT GENERATING ANMATION FILE AND THE SYSTEM IS NOT RUNNING FOR VOLUME FRACTION OF GAS, GAS PRESSURE AND VELOCITY VECTORS.
3. I NEED THE UNITS OF THE PRESSURE, GAS VELOCITY IN THE SYSTEM RUNNING FILE BUT NOT ON THE SCALE OF (0-1).

stlmainchemloop.mfx (10.1 KB)
geometry.stl (4.4 MB)
geometry_0005.stl (3.7 MB)

[cgw]

@sayyamchopra - this case does not run for me.

I’m getting:

Error: NO CARTESIAN GRID BOUNDARY CONDITION SPECIFIED.

AT LEAST ONE BC_TYPE MUST START WITH CG (FOR EXAMPLE CG_NSW)

RUN ABORTED

Are you sure you attached the right files?

[sayyamchopra]

Hi, thanks a lot for the reply. Yes@cgw , i have attached the right files. Yet, i will again attach the new files with improved geometry. Few days ago, someone from MFIX suggested me to use a different software to design the geometry and i did it.
I am using DEM modelling to simulate chemical looping rector and i am currently using 4mm particles and the mesh i have used is as fine as possible with a condition that the CELL SIZE > particle size with KMAX value being 3 times particle size.
Also, a new highlight is that, i used ANSYS AND AUTOCAD TO DESIGN A NEW GEOMETRY. I was planning to post a new question, but since i got a reply from you, i will post all my queries in the current forum. I will highlight the issues i am facing and the corrective steps i have already tried.

Issues i am facing:

1. Dt< Dt min. I know this error means that there is a convergence problem. I have read several forums considering this issue, and i have tried the following actions:
   a. Reduced DOT PRODUCT TOLERANCE and SMALL CELL TOLERANCE and increased the NO OF FACETS to improve mesh. (NO IMPROVEMENT)
   b. Played with variable values of VOLUME FRACTION OF SOLID from 0.4-0.55. (NO IMPROVEMENT)
   c. Reduced the spatial discretization values for certain parameters from 0.5 to 0.4. (NO IMPROVEMENT)
   d. Improved the value of MAXIMUM TIME STEP and MINIMUM TIME STEP. (NO IMPROVEMENT)

Also i do not understand the meaning of (Number of active facets (BCs not flush with MFiX box)). This is what i see when i apply meshing.

Please help me with this problem. I think i have tried almost everything and i still cannot understand the issue. I need some expert suggestions and advice. I need to understand if there is an issue with my geometry or if there is a bug error in the system that the system does run properly which i highly doubt because the software and the new version seems to be very good.

thanks for the help in advance.

chemlooptry4.mfx (12.9 KB)
CHEMLOOPTRY4.msh (39.0 MB)
CHEMLOOPTRY4_FACETS_IGNORED.stl (27 Bytes)
try4.stl (97.7 MB)

Dropbox - chemlooptry4_2022-08-24T110313.424558.zip - Simplify your lifezip files and bug report

[jeff.dietiker]

Most of your questions have already been answered in previous posts. The most important is the grid spacing relative to the wall thickness, which needs to be addressed (ISSUE WITH USING TWO FLUID MODEL (MFIX-TFM) AND Dt < Dt min ERROR - #4 by jeff.dietiker). You mesh is still too coarse to resolve the vortex finder and loopseal internal wall.

[sayyamchopra]

Hello Jeff, thanks for the reply. I really don’t understand the meaning of grid spacing. According to my understanding, grid spacing is where you define mesh size and define the value of IMAX/JMAX/KMAX. Also, i am not sure, but i hope if you could clarify one of my doubt that is, " Can i set the cell size in meshing to be smaller than the particle size?".

Can you please elaborate what do you mean when you say " Improve meshing" . How do i do it?