Cavitation Inception Scale Effects. 1. Nuclei Distributions in Natural Waters. 2. Cavitation Inception in a Turbulent Shear Flow.
Abstract
Experimental investigations were made into the two major aspects of cavitation scale effects, susceptibility of the water to cavitation and flow field effects. In situ investigations of marine cavitation nuclei populations were made using underwater holography. Relatively high bubble concentrations during calm sea conditions, and their population inversion below the thermocline where organism activity was high, indicate a possible biological source of bubble production. Measured bubble sizes can be used to indicate that the average tensile strength of the ocean waters examined should be on the order of several thousands Pascals, with a minimum expected value of about one hundred Pascals. A concentration of at least 3 bubbles per cu cm in the 5 to 20 micrometers radius range is needed in test facility water to model marine conditions. The inception processes in a turbulent free shear layer were examined at Reynolds numbers up to 2 million. Two distinct types of vortex motion were evident, the primary spanwise and the secondary longitudinal vortices. Cavitation inception occurs in the secondary shear layer vortices and more fully developed cavitation is visible in both structures. A Rankine vortex model indicates that the secondary vortex strength is less than 10% of that of the primary structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1987
- Accession Number
- ADA186553
Entities
People
- Timothy J. O'hern
Organizations
- California Institute of Technology