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SUMMARY:On the origin of the hydraulic jump in a thin liquid film  - Rajat
  Bhagat\, Dept of Chemical Engineering\, Uni of Cambridge
DTSTART:20180503T103000Z
DTEND:20180503T113000Z
UID:TALK104395@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION: For more than a century\, it has been believed that all hydra
 ulic jumps are created due to gravity. However\, we found that thin-film h
 ydraulic jumps are not induced by gravity. This study explores the initiat
 ion of thin-film hydraulic jumps. For circular jumps produced by the norma
 l impingement of a jet onto a solid surface\, we found that the jump is fo
 rmed when surface tension and viscous forces balance the momentum in the f
 ilm and gravity plays no significant role. Experiments show no dependence 
 on the orientation of the surface and a scaling relation balancing viscous
  forces and surface tension collapses the experimental data. Experiments o
 n thin film planar jumps in a channel also show that the predominant balan
 ce is with surface tension\, although for the thickness of the films we st
 udied gravity also played a role in the jump formation. A theoretical anal
 ysis shows that the downstream transport of surface tension energy is the 
 previously neglected\, critical ingredient in these flows and that capilla
 ry waves play the role of gravity waves in a traditional jump in demarcati
 ng the transition from the supercritical to subcritical flow associated wi
 th these jumps. 
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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