Instability of Ventilated Cavities
1959-11
Loading...
View/Download File
Persistent link to this item
Statistics
View StatisticsJournal Title
Journal ISSN
Volume Title
Title
Instability of Ventilated Cavities
Authors
Published Date
1959-11
Publisher
St. Anthony Falls Hydraulic Laboratory
Type
Working Paper
Abstract
Cavitation number σ is defined by σ = (P_o - P_k)/q. It can be controlled by controlling the dynamic pressure q, the ambient pressure P_o, or the internal cavity pressure P_k. The present investigation was undertaken
to study methods of controlling P_k by adding air to the wakes of fully submerged
bodies. This process has been called ventilation.
It was found that with P_o and q fixed, P_k increases, and hence σ decreases, nearly linearly with the rate of air supply. Numerical values are given in the paper for the normal flat plate, circular cylinder, and various hydrofoils, and these values may be extrapolated to other sizes of bodies
than those tested.
It was also found that once σ was decreased to a certain critical value, further increase in the air supply rate would not produce a continuing linear decrease in σ. Rather, σ remained nearly constant and the cavities began to vibrate. Vibration occurred with one, two, or more waves on
the cavity surface. Only by going from a one-wave to a two-wave cavity could
σ be reduced further, and the reduction was discontinuous . A detailed description
of the vibrating cavities is given.
Both two-dimensional and finite aspect-ratio bodies were tested. The tests were conducted in the two-dimensional, vertical, free-jet water tunnel at the St. Anthony Falls Hydraulic Laboratory. All bodies tested, regardless of aspect ratio and whether lifting or nonlifting, behaved quite
similarly within both the vibrating and nonvibrating regimes. That the vibration
was not peculiar to the vertical free-jet tunnel was demonstrated by comparison with results from a hydrofoil towed in a tank. In the case of lifting bodies of finite span operating near a free surface, air was found to enter, rather than leave, the cavities through the trailing vortexes.
Keywords
Description
Contract Nonr 710(24), Task NR 062-052
Related to
Replaces
License
Collections
Series/Report Number
Funding information
Office of Naval Research Department of the Navy
Isbn identifier
Doi identifier
Previously Published Citation
Suggested citation
Sliberman, E.; Song, C. S.. (1959). Instability of Ventilated Cavities. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/108041.
Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.