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SUMMARY:An optimal transient growth of small perturbations in thin gaseous
  discs - Viacheslav Zhuravlev (Sternberg Astronomical Institute\, Moscow)
DTSTART:20110926T150000Z
DTEND:20110926T160000Z
UID:TALK32558@talks.cam.ac.uk
CONTACT:Henrik Latter
DESCRIPTION:If the matter rotates around a point-mass gravitating body it 
 can form\nan axisymmetric torus that has a rotational profile determined b
 y its\npressure gradient distribution. Although a thick torus with a\nnon-
 keplerian rotation bounded by the free surface has a set of global\nexpone
 ntially growing modes when it approaches a thin disc with an\nalmost keple
 rian rotation this global acoustic instability ceases\npromptly and we get
  a nearly stable shearing flow. However\, a\nsubstantial transient growth 
 of linear perturbations measured by the\nevolution of their acoustic energ
 y is possible even in this case. This\nfact is demonstrated for a simple m
 odel of a non-viscous polytropic thin\ndisc of a finite radial size where 
 small global adiabatic perturbations\nare considered as linear combination
 s of neutral modes with a\ncorotational radius located beyond the outer bo
 undary of the flow.\n
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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