On the Flow Structure, Tip Leakage Cavitation Inception and Associated Noise

The objective of this study is to investigate the effect of gap size on the flow structure and on the inception of tip leakage cavitation. Controlled cavitation tests were performed after de-aerating the water in the tunnel and using electrolysis to generate cavitation nuclei. The experiments consisted of simultaneously detecting cavitation inception using a 2000fps digital camera (visual) and two accelerometers (“acoustic”) mounted on the test-section windows. Good agreement between these methods was achieved when the visual observations were performed carefully. Portions of the signal containing cavitation noise were analyzed using Hilbert and Wavelet transforms. In order to obtain the time dependent spectra, rates of cavitation events as a function of the cavitation index (σ) for the 3 gap sizes (0.6, 1.4, 2.6mm) were measured. The observations clearly demonstrate that high amplitude noise spikes are generated when the bubbles are distorted and “shredded”—broken to several bubbles following their growth in the vortex core. Mere changes to bubble size and shape caused significantly lower noise. High resolution Particle Image Velocimetry (PIV) (a vector spacing of 180μm) was used to measure the flow, especially to capture the slender tip vortices where cavitation inception was observed. Seventy instantaneous realizations for the 0.6mm gap and 65 for the 1.4mm gap were analyzed to obtain distributions of circulation of the leakage vortex. PIV experiments for the 2.6mm gap are presently underway and only instantaneous samples are presented. The vortex core diameter was found to be 3–4 vector spacings. Minimum pressure coefficients in the cores of these vortices were estimated using a Rankine model. These coefficients showed a very good agreement with the measured cavitation inception indices.

• Record URL:
  • http://www.nap.edu/catalog.php?record_id=10189
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/9780309254670
• Corporate Authors:

  Office of Naval Research

  Department of the Navy, 800 North Quincy Street
  Arlington, VA  United States  22217

  Bassin d'Essais des Carenes

  Chaussee du Vexin
  Val-de-Reuil,   France  27100

  National Research Council

  Naval Studies Board, 500 5th Street, NW
  Washington, DC  United States  20001
• Authors:
  • Gopalan, Shridhar
  • Liu, Henry L
  • Katz, Joseph
• Discussers:
  • Chahine, Georges L
  • Hsiao, Chao-Tsung
  • Farrell, K J
  • Straka, W A
• Conference:
  • Twenty-Third Symposium on Naval Hydrodynamics
  • Location: Val de Reuil , France
  • Date: 2000-9-17 to 2000-9-22
• Publication Date: 2001

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References;
• Pagination: pp 639-653
• Monograph Title: Twenty-Third Symposium on Naval Hydrodynamics

Subject/Index Terms

• TRT Terms: Acoustics; Bubbles; Cavitation (Mechanics); Experiments; Test facilities; Vortices
• Uncontrolled Terms: Particle image velocimetry
• Subject Areas: Marine Transportation;

Filing Info

• Accession Number: 01369716
• Record Type: Publication
• ISBN: 9780309254670
• Files: TRIS
• Created Date: May 11 2012 9:05AM