106 



TABLE IV COMPARISON OF NUCLEI MEASUREMENTS 



Investigator 



Measuring 

 Technique 



Facility 



Conditions at time 

 of Measurement 



Gavrilov (1970) 

 Peterson et al (1975) 



Acoustic 



Light Scattering 



Holography 



Microscopy 



Water Tunnel 

 at TDF 



Standing tap water 



At inception on 50 mm diameter 

 NSRDC body o = 0.49 



Arndt & Keller (1976) 



Light Scattering 



Water Tunnel Cavitation tests on a sharp edged 

 at NSMB disc. Air contents: 6.3 and 



12.5 ppm 



Keller & Weitendorf (1976) Light Scattering 



Water Tunnel 

 at Hamburg 

 Model Basin 



Propeller test, gassed water, 

 Air content: ~30 ppm 



Medwin (1977) 



Acoustic 



Monterey Bay, Various depths and seasons 

 California 



Peterson (1974) 



Coulter Counter 



Santa Catalina Various depths 



Channel 



California 



U.S. Navy (Naval Ocean Coulter Counter 



System Center, San Diego, 

 California. Courtesy 

 Dr. T. Lang) 



San Diego Bay Various depths 

 and offshore 



Present Tests 



Holography 



LTWT 



Air content-^ 7 ppm, = 0.44 



E 



2 

 O 



a. 



PETERSON elal 

 ■il975)(cr = 0.49. 

 SCATTERING 



PETERSON elol 

 (I975)((T = 0.49. 

 HOLOGRAPHY) 



GAVRILOV 



(1970) 



(FRESH WATER) 



5 10'° 



O 



cr 



LlJ 

 CO 



3 



10" 



' PRESENT TESTS LTWT 

 AIR C0NTENT~7ppm . 

 tr = 0.44 



GAVRILOV (1970) 

 (AFTER STANDING 

 5 HOURS 



MEDWIN (1977) 

 (OCEAN, FEBRUARY) 



ARNDT a KELLER 



(1976) 



AIR CONTENT- 



12.5 ppm 



KELLER a 

 WEITENDORF 

 (1976) 



GASSED WATER 

 AIR CONTENT- 

 SO ppm 



ARNDT a 

 KELLER (I976T 

 AIR CONTENT- 

 6.3 ppm 



MEDWIN (1977) 

 (OCEAN. AUGUST) 



10 100 



RADIUS R (micrometers) 



FIGURE 43. Nuclei distributions from various sources. 



micrometers. Further, in the winter the measured 

 bubble population in the ocean is one order of 

 magnitude less than in the summer. We see then it 

 is actually possible for laboratory facilities to 

 have much higher nuclei populations than actually 

 occur in the ocean. Medwin concludes interestingly 

 that the microbubbles had a biological as well as 

 physical origin because the concentration of bubbles 

 increased with depth. This observation is perhaps 

 of importance for the Coulter Counter measurements 

 of Peterson (1974) and Lang (1977) . The particulates 

 measured there, although thought to be of organic 

 material, may actually also contain some gas. 

 Finally, it is amazing to observe the wide range 

 of applicability of fairly simple power laws for 

 particulate and microbubble populations. 



9. CONCLUSIONS 



It is clear that the onset of cavitation and its 

 physical appearance at this onset can be greatly 

 affected by freestream turbulence and the presence 

 of minute amounts of long chain polymer solutes. 

 The present results support the conclusion that 

 these effects are indirect insofar as cavitation 

 goes and that the primary effect is on the viscous 

 flow past the test body. The polymer solutions in 

 particular promote an early boundary layer transi- 

 tion which forestalls the presence of laminar separa- 

 tion much as does boundary layer stimulation by 

 freestream turbulence or trips. It follows that 

 cavitation on bodies not having laminar separation 



