# Application of Bernoulli's equation between stationary and moving reference points

I'm working on a pipe design problem using Bernoulli's equation, from first principles. The pipe is from a water storage reservoir (point 1) and discharges into a river (point 2). These are my two reference points respectively.

Now I know that the velocity at the reservoir is zero (point 1) as the water level is assumed to be stationary, but is the velocity at point 2 equal to the speed of the river?

This seems to make sense from my understanding as the movement of water in the river would carry some energy which must be considered.

• Is the discharge end immersed in the river? Parallel to flow or perpendicular? Mar 30, 2018 at 15:27
• It would be immersed in the river, and perpendicular to the flow. Mar 31, 2018 at 0:06
• The velocity at P2 is governed by the pipe size and the flow rate in any case. There may be some discharge factor that gets added into the pipe resistance depending on the discharge conditions, but that's how this is accounted for - with a pipe fudge factor, like with elbows and transitions. Aug 17, 2020 at 9:45
• As @PhilSweet hinted, the word "pipe" implies significant viscous forces, and if significant viscous forces are encountered between point 1 and point 2, applying Bernoulli's equation between those points won't work. Apr 15, 2021 at 8:42