# How to calculate the velocity reduction in pipes

I have a big pipe with known diameter, length and velcity at big pipe. There are two pipes dividing form the big pipe with varing diameter and length.
1) How to calculate velocity of water in these two pipes?
2) If I add one more pipe of known length and diameter, what would be the velocity in each of these pipes.

Many Thanks...

## Answers and Replies

mfb
Mentor
You need the pressure at every entry/exit point of your pipe system. Each pipe has a specific relation "flow for specific pressure difference" (where the dependency on the absolute pressure should be small), this depends on the geometry.

Yes, I have pressure value for the pipes. But, it is same for all over the pipe. I won't be able to measure at each entry and exit of the pipes :(

mfb
Mentor
If the pressure is the same everywhere, you cannot get any flow, unless the system has zero friction (in this case, the flow cannot be calculated without knowledge about the remaining system).