Peterson 
tion. These particulate are felt to have a major role 
in the cavity nucleation process. 
INTRODUCTION 
Over the years there has been continued discussion about the 
role of the air content in water on the cavitation inception process. 
Typical recent surveys on the subject have been by Eisenberg Big 
Holl [2] , Knapp [3] , Plesset [4] , and vander Walle [5] . 
Much of the discussion has been concerned with the determination of 
the nature of the "nuclei'' that are attributed to the onset of a vapor 
cavity. At the present time, no conclusive results have been reported 
that fully explain the relative importance of the free stream gas 
bubbles, the unwetted (hydrophobic) solid particles and the gas trap- 
ped in crevices on the test body. Presumably, each of these postu- 
lated nuclei sources will contribute to the formation of cavitation, 
with various degrees of relative importance. The actual importance 
of each during any given test will be dependent on the fluid and body 
characteristics and the pressure and velocity fields. 
What is presently needed is a series of definitive tests that 
would elucidate the role of the various types of nuclei as a function 
of the various controlling parameters. Before this series of tests 
can be performed, an adequate physical understanding must be deve- 
loped to recognize and plan a definitive experiment. It is the aim of 
this paper to assist in extending the presently available knowledge 
on the cavity nucleation process in hydrodynamic cavitation. Since 
the available literature on cavity nucleation has been surveyed by 
many writers, the contribution of the present paper will be concer- 
ned principally with the recent work performed at the Naval Ship 
Research and Development Center (NSRDC). The results of other 
investigators will be considered and compared to the extent that their 
work has a bearing on the interpretation of the observed phenomena, 
The recent cavitation research at NSRDC has been concerned 
with developing a better understanding of the role of the free and dis- 
solved gas content on hydrodynamic cavitation. The emphasis of the 
work reported here will be concerned with the importance of gas bub- 
bles in the free stream for the type of cavitation occurring on one 
headform shape at one velocity in a water tunnel. By restricting the 
test conditions in this manner, changes in parameters such as the 
* References are listed on page 1156. 
1 Bs 74 
