The Pulsation of Ventilated Supercavities
Open Access
- Author:
- Skidmore, Grant Marston
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 08, 2012
- Committee Members:
- Jules Washington Lindau V, Thesis Advisor/Co-Advisor
Timothy A Brungart, Thesis Advisor/Co-Advisor
Robert Francis Kunz, Thesis Advisor/Co-Advisor - Keywords:
- Supercavitation
Pulsation
Cavitation
Oscillation
Resonance
Ventilated Supercavities
Two Phase Flow - Abstract:
- Supercavity pulsation is a self-excited resonance phenomenon that destabilizes a supercavity and leads to the periodic release of gas pockets at the tail of the cavity. Previous literature suggests that this phenomenon requires a free surface to occur and that the blockage from a narrow, rigid wall tunnel would not allow for the cavitation number, σ, to be sufficiently low for pulsation to be initiated. Utilizing the 0.305 m and 1.212 m diameter water tunnels at ARL Penn State, an experimental study on both the pulsation phenomenon and the effects of tunnel blockage has been conducted. In parallel to this study, a computational study on the same topics has been conducted using the CFD code, UNCLE-M. This thesis presents a summary of the investigation performed on pulsating ventilated supercavities and the effects of blockage on their formation. Pulsating supercavities were generated in the 0.305 m water tunnel in both a fully filled and a partially filled condition. It was found that the rigid walls of the tunnel served to shrink the envelope of conditions over which pulsation could occur, but they did not inhibit pulsation entirely. The effects of blockage were examined and distinct differences in closure regimes were observed at identical test conditions depending on whether the experiments were performed in the 0.305 m or 1.212 m water tunnel. The twin vortex closure regime was found to be dominant in the 0.305 m water tunnel, whereas the re- entrant jet closure regime was found to exist over a much wider range of conditions in the 1.212 m water tunnel compared to the 0.305 m water tunnel. Finally, a previously undocumented hybrid closure regime was discovered; a stable, hybrid twin vortex and pulsating cavity closure regime characterized by traveling surface waves propagating down the hollow vortex tubes of the twin vortex closure.