Frequently I have to analyse the pressure drop through a piping, and many times I face the same problem: the goals do not converge rightly.
Here is a simple example: a linear pipe with diameter 250mm, and lenght 15m.
Outlet velocity = 30 m/s
Static pressure at the inlet = 101325 Pa
Real wall at pipe faces
The fluid is air
Static pressure at the outlet
So the pressure drop will be (static pressure at the inlet - static pressure at the outlet)
I've set the goals convergence as the unic stop criteria, and changed the delta to 10Pa.
Here are the results:
As you can see, the static pressure at the outlet is varing more than 5000Pa even in the last interactions, what is a hugeness.
Does someone know why is this happening, and how to solve the problem?
It is interesting to note that if I reduce the pipe's lenght, to 5m for example, the goal converge well.
Thanks for your attention!