# How can I determinate the air flow coming out of a pressure tank?

I have a trouble with a simple question (I think). Well, if a have a tank full of compressible air at a pressure of for example 6 bar and a valve with a hole of 8 mm diameter, how can I know the volumetric flow coming out of the valve in function of the actual pressure? The temperature of the ambient is 20 °C and a pressure of 1 bar. I had been searching the way to resolve it but I'm confuse because all the problems I find about compressible air are about turbines and others with not straight out pipe. Thanks for your responses.

• Not a simple question. Search "The flow of air through circular orifices with rounded approach" – pentane Nov 2 '16 at 21:25

For this case: $$\frac{v^2}{2}=\frac{p}{\rho(p)}$$ Where $\rho$ is dependent on the pressure. I figured something around 380 meters per second, but at such high speeds, friction might play a non-neglectable role.