# How to obtain pressure from flow rate just near the outlet of pipe?

All i found related to this question is Hagen-Poiseuille equation, but it is not suitable for the ending of pipe.

I want to know what is the pressure of the gas after it is expelled from the pipe. I only know flow rate and diameter of pipe.

## 2 Answers

If the gas velocity is subsonic, then the pressure at the outlet of the pipe is the ambient pressure.

• Even if it blows at the plate, located very close to the outlet? Feb 2, 2017 at 8:45
• What plate are you talking about?
– Pirx
Feb 2, 2017 at 12:39
• flat plate, perpendicular to the pipe. About 0.2mm between plate and the pipe's outlet. Feb 2, 2017 at 14:37
• What size pipe, what flow rate, what fluid? That would be the minimum amount of information required to even understand what you are talking about. There's a good chance, however, that the answer to your question will not be easy to obtain from first principles. If this is an engineering problem, you may want to ask in the engineering forum.
– Pirx
Feb 2, 2017 at 14:42

At the outlet the pressure will be the same as ambient (atmospheric?) pressure.

• Even if it blows at the plate, located very close to the outlet? Feb 2, 2017 at 8:46