"Error 1000: Cannot locate flow plane for boundary condition" Boundary Condition Error On Imported STL

[kevan]

Hello. I have a fairly basic geometry that I imported into MFiX as STL files, but when I go to run the simulation there seems to be an error associated with the definition of the top outlet boundary condition. When importing the individual STLs I made sure to flip the normals such that they are pointing inwards. In the past I have solved this issue by adjusting the background mesh resolution along the z axis, but I don’t understand why this fixed this issue and I do not want to relay on this as the only solution going forward. I have also defined the outlet below the z_max value so that STL files extends past the geometry I am trying to mesh, in order to hopefully get a higher quality mesh. I am wondering if the issue is perhaps with the resolution and intersection of the STL files with the background mesh or outlet plane? Any help or guidance in understanding this error message and how to fix it would be very beneficial. Thank you for your help.
DEMIndividualSTL.zip (1.1 MB)
MeshTestingBasedOnTutorial.mfx (12.4 KB)

Attached is a compressed folder of the entire case, the .mfx file and a screenshot of the exact error message.

[jeff.dietiker]

I don’t really understand your Boundary Conditions, but your stl geometry is completely closed up. Even what you call inlet.stl and outlet.stl are used as no-slip wall.

The zmax boundary is located at z=0.401 m but you apply an outlet BC at z=0.4m. This is OK for a coarse mesh, because the BC plane coordinate snaps to the closest grid point. This doesn’t work with fine mesh (DZ=0.5mm, smaller than the difference between zmax=0.401m and z=0.4m) because now the z=0.4m plane is located inside the domain and is not a boundary anymore.

There is also a conflict since you define both an outlet and a wall at z=0.4m