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SUMMARY:From the dynamics of a hydraulic jump to the the asymmetric charac
 ter of stellar explosions - Thierry Foglizzo (Service d’Astrophysique\, 
 CEA Saclay)
DTSTART:20161121T160000Z
DTEND:20161121T170000Z
UID:TALK69026@talks.cam.ac.uk
CONTACT:Jean Teyssandier
DESCRIPTION:\nThe explosion mechanism of massive stars is a challenging pr
 oblem where multidimensional instabilities seem to play a central role.\nN
 on axisymmetric instabilities such as the Standing Accretion Shock Instabi
 lity and neutrino-driven convection are able to break the spherical symmet
 ry and impact the birth condition of pulsars.\nSurprisingly\, the SASI ins
 tability can be illustrated with a simple experiment based on a shallow wa
 ter analogy.\nThe SWASI fountain involves a circular hydraulic jump in a r
 adial converging flow\, which becomes oscillatory and turns into a self su
 stained rotating pattern. \nNumerical simulations and a perturbative analy
 sis suggest that this unstable dynamics is due to the interaction of vorti
 city and surface gravity waves. \nThe most recent experimental setup uses 
 the global rotation of the fountain to study the redistribution of angular
  momentum in the collapsing stellar core. \nA new m=1 spiral mode reminisc
 ent of the Papaloizou-Pringle instability\, fed by differential rotation\,
  has been characterized experimentally using surface PIV. \nResults are di
 scussed in view of the constraints set by stellar evolution and by the spi
 n properties of pulsars.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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