Outlet vents to atmosphere
 

I have an outlet that vents to the atmosphere. My reference pressure is 1 atm. So would my outlet have a relativve pressure of 0 or 1 atm?

Re: Outlet vents to atmosphere
 

I struggled with the same problem. I tried to do an analysis with high velocity jet. The orifice is obviously very small in diameter. The length of the orifice is about 10 times the diameter. But, I don't think the flow is anywhere close to "fully developed". Due to the high pressure drop, I think there's got to be a large difference in pressure between the two side of the exit. I don't really know whether I should use 0 as the outlet pressure.

Looking forward to hearing your advices.

Re: Outlet vents to atmosphere
 

Think of the relative pressure as a gauge pressure. If the reference pressure is 1 [atm] and your outlet pressure is 1 [atm], then the gauge pressure is 0 [atm].

Prel = Pabs - Pref

-CycLone

Re: Outlet vents to atmosphere
 

That's what I thought, thanks CycLone