*Hello,I'm assuming that your flow is incompressible. Is that the case?To set-up the problem, you can use pressure inlet and pressure outlet conditions. You might need to fix the pressure outlet and the parameter of interest will be the overall mass flow rate at the exit. You will need to keep changing the outlet pressure until you obtain the correct mass flow rate. I think you might want to define your problem a bit more. Minimum diameter can be any value. As you shrink your diameter, your overall pressure drop will keep rising and you will need a larger driving pressure. Depending on the Reynolds number and the overall geometry of your distributor, you might have to make some assumptions if you are looking for a hand calculator. However, if your geometry is complex, these hand calculations could be way off. I hope these comments provide some help.Karthik*https://forum.ansys.com/discussion/comment/101322#Comment_101322