I have reactor that looks as follows :
In the first part, my reactants flow in. The reaction is started and generates heat as a result.
It then expands slightly into the second part where after it is forced through a smaller opening, compressing the gases. The compressed gas then once again expands.
The reactor kinetics are not that important for now, I can do that. However, I do not know how to use NS-equations where the fluid expands, compresses and then expands.
I only ask that someone throws me in the right direction so that I may further research this.