When I model the internal flow of the pipe, I set mass flow inlet and pressure outlet, and I can observe the internal flow in the pipe. If I want to know the velocity after 2mm of the pressure outlet, what should I do?

First, set second model. The pressure outlet of first model is set as mass flow inlet of second model and other boundaries as pressure outlet. (For mass conservation, so the two mass flow inlets are the same, right?) And how far should I define the boundary field? (The area of mass flow inlet is 0.08*2660)

Second, extend the pressure outlet of the first model. The model has another walls, and what types of this wall will be define? (symmetry, pressure outlet, or...)

Thanks a lot

sincerely

well , i think your first idea of modellin the outer region beyond the pipe outlet sounds good, basically u got make a far field model like a big box just outside the outlet of the pipe , but now the BC for the pipe shouldnt be named as pressure outlet but name it as interior cause now your pressure outlet BC are the sides of the box which basically acting as a far field .one of the sides of the box will also be symmetry BC

i hope this helps u