Hydrodynamic cavitation inception

The effect of polymeric additives on collective phenomena, associated with the dynamics of bubbles, can be illustrated by the example of hydrodynamic cavitation, caused by abrupt decrease in local pressure (in flows around bodies, after stream contraction, in jets). It has been found that the use of polymers permits to decrease the cavitation noise, lower the cavitation erosion, and delay the cavitation inception. For example, adding a small amount of POE to a water jet issuing from the orifice caused the decrease of the critical cavitation number, K , by 35-40%. In experiments with rotating disk flic value of K, was decreased by 65% with addition of 500 ppm POE. Note, however, that these features are linked not only to the changes in individual bubble dynamics, but to the influence of macromolecules on the total flow regime as well. In particular, phenomena listed above are... 

The prediction of the inception of cavitation is, of course, closely related to nucleation theory, but has generally been studied experimentally by modeling with reference to the hydrodynamic flow field (El, L7, S15). The usual criterion is the Prandtl cavitation number (M6),... 

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