Well, how I can determine the drop pressure in a duct? If, at inlet I have a Mass Flow of 1 kg/s and a gauge pressure of 200 kPa. But at outlet I do not know the gauge pressure and I want to hold the same mass flow.

How I could Initialize the case??

Hello,

You'll have the same mass flow at outlet as a result of the continuity equations - in fact you'll have a result slightly different because your numerical error.

And the variation of pression you'll have as the result of solution of momentum and mass continuity together.

So, for you to do it with Fluent, you just set a inlet of "mass flow inlet", and a outlet of "outflow".

You don't have to worry about setting the 200kPa at the inlet, because what matters is just the variation in the duct, and not the absolut value - i.e. 200kPa at the inlet and 100kPa at the outlet is the same thing* as 500kPa in the inlet and 400kPa at the outlet.

I'd initialize all the domain with 200kPa.

My best regards, Victor

*I suppose you're not dealing with a compressible flow.

If I am correct you dont have to do anything! Just application of Inlet mass flow rate of 1kg/s and Gauge pressure of 0 (pressure outlet) at outlet would do for you. Measure the Pressure at the inlet after the solution and thats your drop in pressure! Again Incompressible flow only!

Jha