Issue of normal recognition in STL files

MFiX
1

Hello developer, after importing the external STL file, I found that there was an error in normal recognition. This geometric model is a quasi-two-dimensional bed with a gas nozzle in the middle. The normal direction of the nozzle should be inward. Currently, an outward normal direction will cause an error in the calculation domain. The case and the geometric model file are here. I would like to ask if you have any good solutions?

78d220dacab7fefc894eddb7424585f
78d220dacab7fefc894eddb7424585f615×725 80.6 KB

0.48_nozzle.mfx (14.9 KB)
geometry.stl (39.4 KB)

2

shot-2025-07-23_10-28-49
shot-2025-07-23_10-28-49963×671 133 KB

3

The problem is that the normal direction of the quasi two-dimensional bed and the nozzle is opposite, and I cannot solve the problem by flipping the normal direction. What should I do when modeling geometry with the nozzle inside the fluidized bed?

4

Can you split the STL file into two components?

5

There are several issues here:

  1. Please use the “Submit bug report” in the main menu to bundle all files, and attach the zip file. Here we need 2-1.1_0.1.STL to open the project, not geometry.stl. When files are missing, it is either impossible to open the project, or it takes extra steps and guesses that will slow down the response you get.
  2. You should not include the MFiX rectangular box in the STL file. Boundary Conditions that are applied along the MFiX box are handled as plane BCs.
  3. You only have one cell in the z-direction and the mesh size is larger than the cylinder diameter, so you won’t be able to resolve the geometry anyway.

If you want to setup a quasi 2D simulation, just use the regular BCs, no STL file. To represent the nozzle, set a rectangular region for the blocked volume (nozzle), apply a NSW BC to it, and set a plane region where the inlet is (around y=0.05m) and apply a Mass Inlet BC to it.