2. Concepts of wave propagation in a fluid medium

2.1 Mechanism of wave propagation

If, in a continuous medium at rest, we cause the rapid displacement of an element, we find that the neighboring elements move and act in turn on the particles in contact; thus, the displacement propagates, from close to close, with a finite speed throughout the medium.

If the shaking is of low amplitude (which will be the case in the study of water hammer), the speed of propagation is called the celerity of sound and is usually denoted by a.

In a fluid, this propagation takes place in the same direction as the shaking. At the same speed, it is accompanied by a variation in pressure, density and temperature. This moving domain, relative to the fluid, constitutes a wave. For example, in an indefinite fluid...