What is Cavitation?

Cavitation is the formation of cavities, or bubbles, in a liquid.

Typical Examples of Cavitation

  • a reduction of the ambient pressure (for example, bubbles behind a boat propeller.)
  • an increase in the temperature (for example, bubbles formed in common boiling.)

    • What did my group do in this subject?

    Because liquids can sustain certain tension like solids before they break apart, there must be a upper limit of this tension. This limit is called the tensile strength of the liquid. In the past ten years, my group has been working on the tensile strength of liquid helium at the temperature range from 0.7 K to 5 K. (Our fellow group in Paris has been working on this similar problem at sub-Kelvin temperature range.)
    Helium is the simplest and most understandable material, and the fundamental properties of liquid helium has been studied very well over wide temperature and pressure ranges. But helium has so many unique characters that helium is still one of the materials which is still being studied a lot all over the world. Liquid helium can be prepared extremely pure (all other materials can be frozen out) and it wetts almost any kind of material (no trapped vapor pockets would be attached on the container wall) so that it is a perfect object for studying cavitation. In additions, helium has two different stable isotopes, helium-3 and helium-4. They are completely different from the point of view of statistical mechanics. One obeys Fermi statistics, and the other obeys Bose statistics. And because liquid helium stays liquid state under its own vapor pressure even the temperature is as close to absolute zero as possible, quantum phenomena can be observed macroscopically.
    We have reported cavitation in bulk liquid helium-4, cavitation associated with electron bubbles in liquid helium-4 and helium-3, and cavitation possibly associated with electron bubbles trapped on quantized vortices in superfluid liquid helium-4. We have also proposed a theory about how the bubble chamber works in the view of cavitation and examined the possibilities to see quantum tunneling from an electron bubble.

    Typical experimental setup

    Here I am only going to describe one of our experimental setup which is used in the helium-3 experiment with electron bubbles. The cell is designed so that only small amount of liquid helium-3 is used. The electronics setup is used for all our recent works with only minor modification for different applications.

    Sample signal recorded by the oscilloscope

    Current work

  • measurement on cavitation associated with electron bubbles trapped on quantized vortices in superfluid helium-4
  • more calculation on cavitation associated with electron bubbles trapped on quantized vortices in superfluid helium-4
  • acoustic measurement about our bubble chamber theory
  • acoustic measurement of solid nucleation in liquid helium-4
  • homogeneous cavitation in liquid helium-3
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