Cavitation is the formation and collapse of small vapor cavities or bubbles in a liquid. It usually occurs when a liquid is subjected to changes of pressure such that the static pressure goes lower than the liquid’s vapor pressure which will cause the formation of bubbles in the liquid. When subjected to higher pressure, the bubbles implode. When these implosions happen near a solid material for e.g. pump impeller, the bubbles implode with a microjet hitting the material surface. Repeated bursts of microjets will cause further erosion which spreads and ultimately results in catastrophic equipment failure. Cavitation occurs in pipes and can cause various unpleasant effects such as:
* Material Erosion
* High Vibration
* Decreased flow/pressure
* Equipment Failure
* Increased power consumption for machinery
Studies in cavitation within nozzles have shown that it has a key role in spray dynamics and atomisation efficiency. The geometry, initial conditions and the composition of the mixture are mainly responsible for preserving or damping the transient phenomena. In case of sharp nozzle inlets the fluid flows towards a smaller cross section and accelerates. The fluid reaches its maximum velocity at a short distance from the nozzle inlet. The result is flow separation in the vicinity of the nozzle walls with the stream diameter becoming minimum (vena contracta).