Cavitation refers to a physical phenomenon in which gas-phase cavities (tiny bubbles) are generated and collapse in flowing liquid. It is a result of forces acting on the liquid. When the pressure on the liquid changes rapidly, cavities are formed, and the pressure during this time is usually quite low, approaching a vacuum, aside from the vapor pressure of the liquid itself. When the environmental pressure increases, the cavities collapse, producing powerful shock waves.
Cavitation is one of the main causes of wear in engineering environments: cavities formed near metal surfaces repeatedly collapse, causing cyclic stress and surface fatigue in the metal. The most common examples occur in pump impellers and bends, where rapid changes in liquid direction are most likely to occur. Cavitation is typically classified into two types: inertial (or transient) cavitation and non-inertial cavitation.
Reference: https://en.wikipedia.org/wiki/Cavitation
