We conclude here, our discussion of cavitating internal flows; the 

 field remains extremely active because of the thermo-hydraulic problems 

 associated with nuclear power plants. We have stressed application of 

 these internal flows to pumps because of the relative simplicity of the 

 representation and because of the inherent importance of the subject. As 

 we have seen there are somewhat analogous problems in naval hydrodynamics. 

 Some of these are due to geometric confinement, such as in the testing of 

 unsteady cavitating flows in water tunnels, and others have their common 

 origin in the liquid environment itself. 



SUMMARY 

 It has been nearly ten years since "Cavitation State of Knowledge" 

 has appeared. Since then, many new lines of research have appeared and 

 some older ones refined. There is now a much clearer understanding, than 

 formerly, of the role of the viscous boundary- layer flow on smooth bodies 

 in cavitation inception. Similarly, the necessity of carefully describing 

 the form and extent of cavitation, both at its onset and developed states 

 for the formulation of realistic physical models, seems well appreciated. 

 New experimental techniques, including the measurement of freestream cavi- 

 tation "nuclei," have appeared; these promise to put laboratory and field 

 studies of cavitation on a new quantitative level. The presently 

 available cavitation- inception scaling concepts are considerably improved 

 and more physically based than formerly. With all these new advances it is 

 still not possible to predict with certainty the location, form, and onset 

 conditions required for cavitation in an arbitrary flow. This is 

 particularly so for unsteady cavitating flows. These flows, in addition, 

 because of the volume change of the cavitation itself, may experience large 

 unsteady interactions with neighboring surfaces or flow fields. Initial 

 attempts at sorting out these mutual effects for certain well-defined 

 hydraulic systems have met with some success. As our observational and 

 methodological techniques improve, there is every reason to believe that 

 our understanding of unsteady cavitation phenomena will continue to im- 

 prove, just as it has for cavitation- inception processes. 



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