Cavitation structures formed during the rebound of a sphere from a wetted surface |
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Authors: | J O Marston W Yong W K Ng R B H Tan S T Thoroddsen |
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Institution: | (1) A-STAR Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore, 627833, Singapore;(2) Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576, Singapore;(3) Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia |
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Abstract: | We use high-speed imaging to observe the dynamics of cavitation, caused by the impact and subsequent rebound of a sphere from
a solid surface covered with a thin layer of highly viscous liquid. We note marked qualitative differences between the cavitation
structures with increase in viscosity, as well as between Newtonian and non-Newtonian liquids. The patterns observed are quite
unexpected and intricate, appearing in concentric ring formations around the site of impact. In all cases, we identify a distinct
radius from which the primary bubbles emanate. This radius is modelled with a modified form of Hertz contact theory. Within
this radius, we show that some fine cavitation structure may exist or that it may be one large cavitation bubble. For the
non-Newtonian fluids, we observe foam-like structures extending radially with diminishing bubble sizes with increase in radial
position. Whereas for the Newtonian fluids, the opposite trend is observed with increasing bubble size for increasing radial
position. Finally, we compare our experimental observations of cavitation to the maximum tension criterion proposed by Joseph (J Fluid Mech 366:367–378, 1998) showing that this provides the lower limit for the onset of cavitation in our experiments. |
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