Ask A Scientist© Engineering Archive

Index Key:   ENG026
Author:      pi
Subject:     Cavitation
Text:        What is Cavitation?

Response #:  1 of 1
Author:      dipper
Text:        I assume that you mean "cavitation" as used in fluid dynamics.  
Cavitation is defined as the process of formation of local cavities is a 
liquid, as a result of the reduction of pressure below a critical value, 
called "vapor pressure."  The most common occurrence of cavitation is in 
propellers, both in water and air.  In the case of a ship propeller, it 
reduces the propulsive force quite a bit.  It also can cause severe damage to 
the propeller itself.  On cavitation, bubbles of vapor start to appear in the 
water.  This  creates an area of extreme low pressure on the propulsion side 
of the propeller.  As the pressure of the surrounding water rises again, the 
vapor bubbles implode, and the water rushes in toward the propeller very fast.  
Because the forces are very high and very concentrated, damage to the 
propeller is likely.  This same principal is true for pumps, hydraulic 
turbines, or anything that is used to create pressure differences in a fluid.  
The results of cavitation are less severe in some fluids than others, 
depending upon the value of its vapor pressure.