HYDRODYNAMIC CAVITATION 
AND SOME CONSIDERATIONS 
OF THE INFLUENCE OF FREE GAS CONTENT 
Frank B. Peterson 
Naval Ship Research and Development Center 
Bethesda, Maryland, U.S.A. 
ABSTRACT 
Hydrodynamic cavitation inception on an axisymme- 
tric body with a 5-cm diameter was measured ina 
standard water tunnel. Particulate matter and free- 
gas bubble size distributions were directly measur- 
ed immediately upstream of the bodies with a high- 
speed holographic technique and related to calculat- 
ed bubble trajectories. Discrimination between par- 
ticulate matter andgas bubbles was possible for dia- 
meters larger than 0.0025 cm. Inception was mea- 
sured acoustically and high-speed movies at 10,000 
frames per second were taken to verify the type of 
cavitation present. The influence of headform sur- 
face chemistry was studied using plastic, copper, 
and gold-plated bodies with and without various types 
of colloidal silica coatings. Physical surface charac- 
teristics were checked with scanning electron mi- 
croscopy. 
All cavities observed in the water tunnel tests were 
approximately hemispherical in shapeand translated 
along the headform surface. When the results were 
compared with previously reported tests in a high- 
speed towing basin, it was concluded that the mea- 
suredfree stream gas bubbles in these standardtest 
facilities did not significantly contribute to the nu- 
cleation of cavitation when acoustic detection was 
used, Other recent research is summarized that de- 
scribes the de novo production of stable hydrophobic 
particulate in water through the mechanism of aera- 
HSI 
