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SUMMARY:Effect of plastron deformation on the wake of super-hydrophobic sp
 heres - Nicolas Mazellier\, University of Orléans 
DTSTART:20180615T120000Z
DTEND:20180615T130000Z
UID:TALK106924@talks.cam.ac.uk
CONTACT:Charlotte Coles
DESCRIPTION:This presentation is dedicated to the experimental investigati
 on of the wake of free falling super-hydrophobic spheres within the so-cal
 led sub-critical regime. It is found that the air plastron adapts its shap
 e to the flow-induced stresses\, which compete with the surface tension. T
 he study of the falling motion reveals that the plastron compliance has a 
 sizeable influence on the wake development. Investigating the lift force e
 xperienced by the super-hydrophobic spheres\, the onset of wake instabilit
 ies is found to be triggered earlier than for smooth spheres used as refer
 ence. Surprisingly\, it is also observed that the early promotion of the w
 ake instabilities is even more pronounced beyond a critical Weber number\,
  which corresponds to a critical aspect ratio of the plastron. Furthermore
 \, the magnitude of the hydrodynamic loads is found to be dependent on the
  average deformation of the gas/liquid interface. Indeed\, in comparison t
 o the reference spheres\, high plastron deformation leads to lift and drag
  increase\, whereas low plastron deformation yields lift and drag mitigati
 on. Accordingly\, taking into account the plastron deformation provides an
  attractive way to explain the somehow discordant results reported in othe
 r studies at comparable Reynolds numbers. The presentation will then focus
  on preliminary results over a broader range of Reynolds.
LOCATION:JDB Seminar Room\, CUED
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