Accession Number : AD0208556

Title :   The Stability of An Air-Maintained Cavity Behind A Stationary Object In Flowing Water.

Descriptive Note : Memorandum rept.,

Corporate Author : CALIFORNIA INST OF TECH PASADENA HYDRODYNAMICS LAB

Personal Author(s) : Swanson, W. W. ; O'Neill, J. P.

Report Date : 05 SEP 1951

Pagination or Media Count : 11

Abstract : Studies of a projectile in an air-maintained cavity were made with supported flat disks in a free-surface water tunnel. Air was injected immediately behind the jet. Curves of entrainment-rate coefficient vs. cavitation number were plotted for a 1-in. disk at 3 stream velocities; each curve shows a minimum. The point of minimum entrainment coincided with a transition from a double vortex to a re-entrant jet configuration. Explanations for the differing slopes on either side of the minimum are given. Using the maximum cavity diameter as a reference length for the Froude number a plot of the entrainment data was made which was independent of nose shape. The extreme slope of the curves at lower cavitation numbers may be due to a double-vortex mechanism which seems to effectively transmit the air downstream. A gravity effect becomes important at low cavitation numbers.

Descriptors :   *CAVITATION, *TRAILING VORTICES, WATER TUNNELS, AIR, ENTRAINMENT, STABILITY, TWO PHASE FLOW, PRESSURE, CAVITIES, FROUDE NUMBER.

Distribution Statement : APPROVED FOR PUBLIC RELEASE