Cavitation structures formed during the rebound of a sphere from a wetted surface
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Mechanical Engineering Program
High-Speed Fluids Imaging Laboratory
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AbstractWe 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. © 2010 Springer-Verlag.
SponsorsThis work was initiated while W. Yong was attached to ICES from NUS during an undergraduate industrial attachment scheme under J.O. Marston. The work was supported by the Science and Engineering Research Council of A*STAR (Agency for Science, Technology and Research), Singapore. The authors would like to thank Ng Junwei for technical support and Professors T. G. Etoh & K. Takehara at Kinki University for use of their laboratory for some early experiments in this work.
JournalExperiments in Fluids