Implicit Functions vs. Primitives

I want to model a right circular frustum fluidized bed. I have two questions.
First, what is the difference between the shape that is generated using implicit functions and primitives?
Second, the reference article that I am re-simulating used an axisymmetric 2D right circular frustum, but as I know, we cannot create the 3D frustum and make it 2D in MFiX (I have used primitives to model 3D frustum). Is there any method to do that?
I have attached the axisymmetric shapes of the FB that I want to model.

The GUI uses VTK to construct STL files that the solver can use (mesh intersection, DEM and PIC collisions). VTK provides two options for constructing geometry:

  1. implicit functions - are functions, the booleans of these functions are robust and don’t fail (segfault)
  2. primitives - are objects represented by triangles. The booleans of these objects can fail (segfault) and cause the GUI to crash.

You could. Create the 3D object and change the boundary extents so that it is a slice of the 3D object (one cell thick). Is this the same as the article’s model? No.

I would also argue that a “axisymmetric 2D” is not accurate, so just run 3D.

1 Like

To check if I have created the geometry correctly, I used the primitives to create a 3D frustum, and I simulated a single phase flow in a nozzle. It worked!! After that, I used the implicit functions to create my frustum (nozzle) to simulate the same single phase flow in a nozzle. It did not converge at all.
Would you please check the file, to see what is the problem?(Uni-directional air flow in a nozzle!)

arastoopour-30July.mfx (10.4 KB)