I have a question: the situation is as follows: There is an open pool (in blue) to which a pipe is connected. The pressure above the pool is equal to the air pressure = 1 bar. In normal configuration the valve from the pipe is closed and thus the pressure in point B is equal to the air pressure + ρgH (hydrostatic pressure). There is no flow through the pipe.
In case there is a rupture of the pipe at the height of the valve, water will siphon from the pool via the pipe at a velocity v. My question is how can you calculate the pressure in point A?
I think the pressure in point A is calculated as follows:
Pa+ $\frac{1}{2}$ρva²+ρgL=Pb+$\frac{1}{2}$ρvb²+ΔPfriction where va=vb and thus:
Pa+ρgL=Pb+ΔPfriction where Pb is equal to the air pressure (1 bar) due to the break.
PA=PB+ΔPfriction - ρgL
ΔPfriction=fD$\frac{L}{D}$$\frac{ρv²}{2}$
However, my friend does not agree with me and says that Pa is equal to Pb. So who is right?