Thanks for letting me know about this. I think I have figure it out to an extent. Although, I am making a mistake somewhere, but I am not able to figure it out. When I patch the phase in Setup, even though I see the phase, there is no interface line and I do not think the phase is being initialized properly.

The converging section is the plastic region and the cuboid part is the air region. I am simulating plastic deposition on the bottom moving plate. As seen in the image below there seems to be some region between the two zones. I do not understand why this is happening. The first four images are plastic inlet, air inlet, outlet and symmetry respectively. The last image corresponds to some patches between the two interfaces, that seem to appear for some reason.

And there seems to be something called "periodic" appearing the BC.

Can you please help me out with this ?. Does this have anything to do with the "describe geometry" option?
Thanks for the help.