How to Know Pressure in Outlet

[dwi.tangerang80]

Hi

How I define boundary coundition to know pressure in outlet, I attach a picture to make the question more clear....

Commonly I just input boundary condition in inlet volume flow rate and pressure, and in outlet I also define pressure 0 ( as I read in help it means that area is outlet), then in result of course we get pressure inlet and outlet same like boundary condition

[Jon.Wilde]

Is it incompressible? Need to know this before I can answer.

You need far longer inlet and outlet lengths also, something like 5-10x longer 😉

[dwi.tangerang80]

Thank you for answer Jon,

The fluid is gas, it should be compressible, but what's the different?

is it possible to know the pressure in outlet even the fluid compressible or incompressible?

yes, I can make pipe longer

[Jon.Wilde]

Sorry, I mean do you need to see the density of the gas changing in this analysis? If not, you can run as incompressible and you would need flow one and end and pressure the other. You can't have two on one end.

What is the Mach number if you run it with a flow rate at inlet and P=0 at outlet? If its above about 0.7, you need to run as compressible, which needs a different setup. Here you could have everything set at the inlet, let's see what the Mach No is first.