Direct Effects of Gravity on Cavitation Bubble Collapse
- Paper number
IAC-07-A2.4.04
- Author
Mr. Aurèle de Bosset, Laboratory of Hydraulic Machines, EPFL., Switzerland
- Coauthor
Mr. Danail Obreschkow, European Space Agency/Student Participation Programme, United Kingdom
- Coauthor
Mr. Philippe Kobel, Max-Planck Institute for Solar System Research, Germany
- Coauthor
Mr. Nicolas Dorsaz, EPFL, Switzerland
- Coauthor
Mr. Mohamed Farhat, EPFL, Switzerland
- Year
2007
- Abstract
We propose an experiment for studying the final stages of collapse of a single laser generated cavitation bubble in microgravity. 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. Previous investigations during the 8th student parabolic flight campaign and 42nd ESA parabolic flight campaign have focused on examining the effect of a spherical water/air interface on cavitation implosion. For the first time, microjet and counterjet formation following cavity collapse were simultaneously observed. As well, additional phenomena resulting from the spherical interface became visible. Finite water volume caused cavity life cycle shortening (Obreschkow et al., 2006). Shockwave confinement created zones of high energy concentration, exciting microbubbles (Obreschkow et al, IAC 2005). This was published in “Cavitation Bubble Dynamics inside Liquid Drops in Microgravity”, Physical Review Letters Vol. 97 No 9. Sept 1, 2006. The direct effects of gravity on the cavity however could not be studied, as the water/air interface directed the geometry of the cavity collapse. Benjamin and Ellis (Mathematical and Physical Sciences, Vol. 260, No. 1110, 1966) demonstrated that large bubbles will deform due to the hydrostatic pressure field in water, influencing the cavity collapse and causing preferential microjet propagation. It is thought that this is a result of the cavity’s sphericity being disturbed by buoyancy forces. This idea is strongly supported by microgravity experiments (Matula et al., Ultrasonics 83, 2000) suggesting that sonoluminescence increases during periods of microgravity. However, the direct role of gravity in single bubble collapses remains poorly understood. From theoretical studies and preliminary ground experiments, we expect that in microgravity a significant amount of the bubble energy would be transformed into a very intense shockwave and increased sonoluminescence, to the detriment of the rebound bubble. In this paper we outline a new microgravity experiment (ESA Parabolic Flight Campaigns) investigating the direct effects of gravity on cavitation bubble collapse. On parabolic flights, it will be possible to compare 3 different gravity levels (0g, 1g, 1.8g) under otherwise identical conditions. The proposed experiment uses a focused laser to generate a highly spherical bubble in an extended water volume without disturbing the liquid. The rapid cavity evolution will be recorded using a fast visualization system (up to 120'000 fps) and shockwaves shall be detected using micro piezo pressure sensors. This setup is quite general, and could equally well be adopted for other forthcoming cavitation studies in microgravity. Such research could give more insight into the possibility of so-called bubble cold fusion and other related phenomenon. Significant insight would be given into the final stages of a nearly perfect spherical bubble collapse.
- Abstract document
- Manuscript document
IAC-07-A2.4.04.pdf (🔒 authorized access only).
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