What is the difference between porous jump and porous zone?
 

What is each one meant for?

A porous zone applies to cell zones (actual volumes) when you want to model the flow inside the porous region.


The porous jump is a boundary/interface condition. You apply this to surfaces (i.e. infinitesimally thin porous regions) where you want to model only the pressure drop effect but not the detailed 3D flow inside the porous material.


It's up to you when you want to use each modeling approach.