ON THE MECHANISM AND PREVENTION OP CAVITATION 



j by 



Phillip Eisenberg 



ABSTRACT 



A brief survey of available information on the mechanism of cavitation is pre- 

 sented with the emphasis on those aspects which are not only of theoretical interest but 

 of interest to the design engineer and naval architect for technical applications. 



The "types" of cavitation are distinguished according to their description by the 

 hydrodynamical equations rather than the thermodynamical and physical-chemical process- 

 es involved. This leads to a distinction between small, individual cavities which oscil- 

 late and eventually disappear, and large, steady-state cavities whose average envelope 

 does not vary with time. The inception of cavitation in pure and in contaminated liquids 

 is discussed. For pure liquids, some recent applications of kinetic theory formulations 

 to the prediction of tensile strength of liquids are presented. Factors in inception that 

 are of more immediate engineering interest are then discussed. These include the roles 

 of surface-active materials and other impurities, air content, turbulence, and pressure 

 gradients in laminar and turbulent boundary layers as related to inception of cavitation. 



Results of analytical and experimental studies of the dynamics of transient, os- 

 cillating cavities are discussed. Tentative descriptions of the mechanism of steady-state 

 cavities in real liquids are given. In connection with the analytical description of such 

 cavities, the results of free streamline theory for two-dimensional cavities with finite 

 cavitation members, and the conclusions obtainable for three-dimensional flows are sum- 

 marized. A treatment of cavities in venturi-type nozzles is proposed in which it is as- 

 sumed that the vapor phase plays no significant role. Computations and experimental 

 results are presented for the latter problem. 



The mechanism of cavitation damage is discussed in terms of both mechanical 

 and electrochemical origins. A few remarks are then made on scaling of cavitating sys- 

 tems and designing for cavitation prevention. In connection with design, some methods 

 that have been proposed for reducing the adverse effects of cavitation are discussed, and 

 some methods available for the prediction of low pressure regions are mentioned. Final- 

 ly, it is shown how cavitation itself may be used for certain cases in designing non- 

 cavitating systems. 



