Text: In a flowing system, the liquid velocity varies locally and at the points of highest velocity, low pressures and cavities occur. Incipient cavitation is the term used to describe the type and stage of cavitation that is just detectable as the cavitation appears. Desinent cavitation is the term used to describe cavitation just before it disappears. The conditions which mark the boundary or threshold between no cavitation and detectable cavitation are not always identical. For example, the pressure of disappearance of cavitation has been generally found to be greater, and less variable, than the pressure of appearance. Three cases of flow cavitation arise: 1. Travelling cavitation occurs when cavities or bubbles form in the liquid, and travel with the liquid as they expand and subsequently collapse. 2. Fixed cavitation occurs when a cavity or pocket attached to the rigid boundary of an immersed body or a flow passage forms, and remains fixed in position in an unsteady state. 3. Vortex cavitation occurs in the cores of vortices which form in regions of high shear, and often occurs on the blade tips of ship's propellers - hence the name "tip" cavitation.

See Also: NEGATIVE ATTRACTION; IMPLOSION; VACUUM; VORTEX; ETHER; SCHAEFFER STEAM MACHINE; SUPERCAVITATION

Source: