The destabilization and subsequent fragmentation of a liquid phase by a turbulent gas phase is  at  the  core  of  many  applications  that  aim  at  producing  high-quality  sprays.  Certain underlying  physical  mechanisms  of  spray  formation  remain  unresolved,  hindering  process efficiency and control. I will present a multiscale characterization of these mechanisms in a two-fluid atomizer, where a round liquid jet is fragmented by a highly turbulent annular gas jet.  The  interfacial  instabilities,  and  resulting  large-scale  dynamics,  are  experimentally characterized  using  two  high-speed  imaging  methods,  back-lit  optical  imaging  and synchrotron  X-ray  radiography.  A  spatial  characterization  of  the  flapping  dynamics  of  the liquid jet indicates that the flapping dimensionality is related to the change between shear break-up to bag break-up. At higher gas velocities, the scaling laws of the transport of the interfacial  instabilities  highlight  the  change  to  fiber-type  atomization.  Similarly,  studying statistics and temporal dynamics of the length of the liquid jet in a broad parameter space poses  a  framework  to  quantitively  describe  changes  in  fragmentation  mechanisms.  In addition,  I  will  show  how  introducing  angular  momentum  (swirl)  in  the  gas  co-flow dramatically  changes  the  topology  and  dynamics  of  the  atomized  liquid  jet,  resulting  in drastic changes in the spray.
 
Coffee and pastries will be served

Contact : olivier.maillet@cea.fr    /    jean-yves.chauleau@cea.fr - Tel : +33 1 69 08 72 16/ 72 17