# Hydrodynamics velocity and speed

1. May 2, 2012

### eagles12

For fluids in motion, how do I find speed using velocity and diameter or velocity and pressure? Like in a pipe or other cyllinder type thing

2. May 2, 2012

### DragonPetter

The relationship between velocity of sound propagation in a liquid medium and the pressure applied on the medium is defined as:

$c = \frac{P}{v*\rho}$

c is speed of sound
P is pressure from sound source
v is particle velocity (not the fluid in motion, as flowing through a pipe, but rather the speed that the particles move from pressure source).
rho is the density of the fluid