Boundary condition error for DEM simulation

MFiX
#1

Hi,

I’m using the DEM method to model gas-solid flows. My geometry is shown below in the first picture, and I want to set the bottom of the internal as the pressure outlet, which is marked in the circle. In the region section, I used a plane to define this area, which is shown in the second picture. Then, I define this area as the pressure-outlet boundary condition. The running reports some errors shown in the last picture. I don’t find any boundary that overlaps with this one. Can you give me some suggestions about how to solve this problem?

geometry
geometry960×950 51.9 KB
region
region880×334 51.5 KB
error
error647×707 236 KB

#2

Please post your files, thus make it easier for others to test your case.

#3

Thank you for your reply. My case is attached.
geometry.mfx (19.2 KB) geometry.stl (33.3 KB) geometry_0006.stl (33.3 KB) geometry_0007.stl (58 Bytes) geometry_0007.stl (58 Bytes) internal.stl (10.2 KB)

#4

It seems that BC(8) you defined overlaps with BC(6) CG-NSW. I tried to change BC(8) to CG_PO by selecting the two facets.

pressure_outlet
pressure_outlet1865×960 103 KB
.While, no matter how I changed the selecting box (red box in the above figure), 10 facets are chosen(Actually I only want to choose the two facets on the bottom). So I have to manually adjuste the file geometry_0008.stl to keep only two facets.
facets
facets988×398 42.5 KB
. Later, I found that CG_PO is currently not supported yet for DEM solver.
pressure_outlet2
pressure_outlet21649×871 96.2 KB
. If you are satisfy with that only gas leaves at BC(8), the code might work after some modifications. Another option is that you can open one or two small pressure outlets (PO) on the front or/and back (XY)plane.

#5

Thank you so much for helping me test the case. I can accept that only gas leave the reactor from BC(8). Can you tell me how to modify the source programme? Thanks again.

#7

I slightly modified several files, while it always diverged after about 20 time steps because the pressure equation can not converge. Thus try other options such as one or two small pressure outlets (PO) on the front or/and back (XY)plane. Other people may have better ideas to solve your problem.

#8

Thanks so much!! Although it doesn’t work, can you tell me which file is modefied by you in the source programme? So I can know how to solve similar problems when I encounter similar problems in future.