I am trying to set up a counter flow of particles and air and I imported an stl file with the required geometry. I get an error saying BC No 2 is not a plane. I am quite new to MFix and I am not quite sure what the error means, and hence how to fix it. I have attached the case and the stl file. Since this is just a dummy case to ensure I can set up the full-scale case, the mesh is quite coarse to speed up the simulation.
Any help will be greatly appreciated. Thank you so much.
There are several issues with your stl file and regions:
The stl geometry has zero thickness wall for the air inlet tubes, where they go inside the vessel. This is not allowed because MFiX cannot have a fluid region on both sides on the wall. This means you have to add thickness to those tubes and you will need a fairly fine mesh to resolve them.
The error message you see is because the y-extents of the Particle Inlet region are flipped. It should go from y=ymin+0.01 to y=ymax-0.01. In the x-direction it should be from x=xmin to x=xmin so it is along the MFiX box.
The top outlet is located above the opening of the stl file. You need to either extend the stl file past z=0.025 or move the top plane below the opening, say at z=0.0249.
The bottom outlet is located in the fluid region. You need to add a rectangular region directly below the MO plane and set this to no-slip wall. Alternatively, you could extend the stl geometry so it goes all the way to the bottom and set the MO at the bottom.