Cavitation Bubbles and Shock Waves Inside Water Drops in Microgravity
- Paper number
IAC-06-A2.P.09
- Author
Mr. Danail Obreschkow, European Space Agency/Student Participation Programme, United Kingdom
- Year
2006
- Abstract
The hydrodynamic cavitation phenomenon is a major source of erosion for many industrial systems such as cryogenic pumps for rocket propulsion, fast ship propellers, hydraulic pipelines and turbines. Erosive processes are associated with liquid jets and shockwaves emission following the cavity collapse. Yet, the relative importance of these two processes remains controversial and this issue requires further cavitation studies inside various geometries of liquid volumes. In particular, one might fruitfully consider bubbles inside spherical isolated water volumes, which is hardly achievable on Earth due to the presence of gravity.
We performed an experimental study of single bubble dynamics inside quasi-spherical water drops produced in microgravity (Parabolic Flights, European Space Agency ESA). High-speed imaging revealed the implications of isolated, finite liquid volumes and spherical free surfaces on the bubble collapse and subsequent phenomena. The experimental data allowed to construct and to verify a novel model of cavitation bubbles in isolated spherical volumes. This model gives quantitative insight in the phenomenon of cavitation in isolated and finite volumes.
A peculiar observation was the simultaneous appearance of transient crowds of micro bubbles (d < 1mm) at the instants of shockwaves emission. We could show that these micro bubbles were induced by the interaction of shockwaves with nuclei and impurities present in the liquid, and because of the shockwaves confinement in an isolated finite liquid volume. These micro bubbles are themselves relevant, since they emit potentially erosive liquid jets as well. However, the shockwaves were not directly observable since their characteristic propagation times across the drop were twice as long as our exposure time (10 µs).
A next participation at parabolic flights (Professional Flight Campaign, ESA, March 2006) will serve to focus on the shockwave-nuclei interactions and to obtain direct shockwaves visualizations. More specifically, sharper images will be achieved by the addition of an ultra-short flashlight, and artificial gaseous nuclei will be introduced in the water volumes.
- Abstract document
- Manuscript document
IAC-06-A2.P.09.pdf (🔒 authorized access only).
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