CAVITATION

This is a tutorial discussion of the present understanding of cavitation phenomena. Fundamentally, cavitation is the boiling of a liquid due to low pressure rather than raised temperature. However, as most liquids contain dissolved gas in solution, which a drop in pressure will release, cavitation may be due (a) to gas release or (b) to low pressure boiling, or in most cases, a mixture of both. If there is gas in the bubble during the first collapse, there is a weak emission of light called sonoluminescence. This may be caused by incandescence of the gas due to the high pressures and temperatures during collapse. The process of cavity collapse is so rapid that very high temperatures and pressures are created. Temperatures as high as 10,000 K have been suggested which may cause rises of 500 degrees to 800 degrees C in the material next to the bubble. Shock waves having a pressure difference of 4000 aim have been demonstrated in the liquid following a buble collapse. The effect of these thermal and pressure shocks on the material, causes mechanical failure, and the erosion, damage. Noise is one of the most characteristic signs of cavitation. Its typical crackling sound covers a wide frequency range up to possibly 1 MHz. The higher frequency noise represents the collapse of small bubbles, whilst large cavities cause low-frequency noise and vibration, which in extreme cases can shake a power station or a ship. Ultrasonic transducers can be used to create cavitation and this is utilized for cleaning purposes. Erosion is caused by thermal and pressure shock waves produced by cavity collapse, and this causes material to disintegrate probably by a fatigue process. Cavitation causes loss of lift and increased drag on the hydrofoils used in high-speed craft, as ship stabilizers, and for a simple representation of pump, turbine and propeller blading. The matter of terminology of pump cavitation is discussed, and from this base pump and impeller design for avoiding cavitation is considered.

  • Corporate Authors:

    Institution of Mechanical Engineers

    1 Birdcage Walk
    London SW1H 9JJ,   England 
  • Authors:
    • Pearsall, I S
  • Publication Date: 1974-7

Media Info

  • Features: References;
  • Pagination: p. 70-85
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00072612
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Dec 31 1974 12:00AM