How to use SHM for this particular case?
 

I have a ventilator fan .stl file. I need to fit this into a rectangular box of particular dimensions. I want this box to be filled with air. I dont have an stl file for this box and hence want to generate this rectangular box in the blockmesh directly.

Here are the following questions I need some help

1) Can i use the required rectangular box dimensions as the base design in the blockMeshDict file or should i define the box and the base design both with their respective dimensions or should i create the box as a .stl file and then use a base design to include both the fan and rectangular stl files? Also can i use the air rectangular box as the refinement region? where should i have the location in mesh? inside ventilator or the air region?

2) for working with MRF we require cellzones, hence howz it possible to obtain the cells for the ventilator and air region seperately? Can i use cylinderToCell in cellSetDict and if i use it does it also include the air regions between the wings of the ventilator?

Can any help me with these issues? :(