Pressure drop in a valve
 

Goodmorning everybody, I need just a little advice. My simulation involve the charaterization of the pressure drop inside a valve. I use mass flow as inlet and pressure outlte as output and that is not the problem. in order to have stability I put the input and the output far from the valve body (very far away: 300 or more milimiters). My question is this one: I should measure the pressure drop right outside the valve or at the input and the output of the domain? Beacuse I get different results.
In my opinion the measurement should be done right outside the valve, that should be more realistic. Because the rest of the hydraulic circuit which I'm working with it is no an half meter straight pipe like in my simulation domain.

Thank you for your time.

Hello based on your problem setting, the pressure drop right before/after the valve should be more relevant, as you said, because it is independent of the artificial extension of upstream/downstream in your simulation domain.

One reminder is to use the total pressure (dynamic pressure plus static pressure) when calculating pressure drop, instead of static pressure, because the latter depends on local cross area and velocity.