Cavitation Susceptibility Measurements of Ocean Lake and Laboratory Waters.
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD
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Ocean and lake measurements were carried out in Exuma Sound, the Gulf Stream off the coast of Florida, and Lake Pend Oreille to provide comparative results in different bodies of water. The test program included cavitation susceptibility measurements by a venturi system, nuclei population measurements by a light scattering device, and a series of standard oceanographic measurements. The depths covered ranged from 10 to 200 m, deeper than ever before for these types of measurements. To provide a reference for comparison between laboratory and natural waters, the same measuring devices were used in the DTNSRDC 12-in. variable pressure water tunnel. There was no difficulty inducing cavitation throughout the test matrix. At depths less than 100 m, the water in the Gulf Stream was found to cavitate more easily than the water in Exuma Sound. At deeper depths, the opposite trend was found. Depending on the nuclei populations, variations of the cavitation inception indices with depth took different forms in Exuma Sound, the Gulf Stream, and Lake Pend Oreille waters. Except at the shallow depths, the lake water was found to be less susceptible to cavitation than the ocean waters. Bubble instability theory and the Rayleigh-Plesset dynamic equation provide good explanations of many of the observed phenomena. The postulation of a critical bubble radius is used to explain the unexpected phenomenon that the concentration of unstable bubbles can increase with depth.
- Fluid Mechanics