Bernd 



faster or slower dissolving than the "prototype" norm, and largely duplicate the 

 action of various natural waters. 



The body of this paper reports upon the basic investigations of surfaces, 

 water, and surface films of gas nuclei. 



CONCLUSIONS 



It was found that usable tensile strength can exist in water in nature; labo- 

 ratory conditions and extreme purity of water are not prerequisites. However, 

 this tensile strength may not be realized because of the nature of the solid ma- 

 terials in contact with the water. Also the maximum tensile strength obtainable 

 may be limited by surface films retarding or preventing the dissolving of gas 

 nuclei entrained in the water. 



On the other hand, fast dissolving water with little film formation can also 

 exist, and should be a partial explanation of the occurrence of tensile strength 

 in water tunnels. 



Surface films about gas nuclei are produced by trace organic materials 

 possessing solubilities in the order of 100 to 10 parts per million. These ma- 

 terials are surfactant; i.e., they are able to migrate to the surface of the nucleus 

 and form a monolayer. Thus a low concentration in solution is brought to a high 

 concentration at the surface. A monolayer is a layer one molecule thick. The 

 monolayer may be surrounded by additional structure -building materials. 



Continued cavitation can remove film-forming materials from action. Un- 

 less they are replenished, a slow dissolving water will ultimately become a fast 

 dissolving water. 



As a result of these investigations, it was found possible to achieve high or 

 negligible tensile strength at will in a small test system. This required the use 

 of suitable solid materials in contact with the water and control of the formation 

 of surface films about gas nuclei. One can therefore forsee the possibilities of 

 the use of such techniques in water tunnel operation or in obtaining higher out- 

 puts from devices normally limited by cavitation. 



WATER/SOLID INTERFACE 



A container, pipe, or some form of solid surface is usually to be fovmd in 

 contact with water. Solids are often present as debris. Therefore the inception 

 of cavitation was measured for different solid materials immersed in "strong" 

 water possessing tensile strength. Thus, the water/solid interface was made 

 the weak link under test. Materials were cemented to the face of a glass-housed 

 acoustic transducer used to produce cavitation. Glass is a "high strength," 

 noncavitating material. Rough screening tests were also performed, using 

 supersaturated carbon dioxide water solutions in contact with the material to 

 stress the water/solid bond. 



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