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SUMMARY:Some decay problems of a collisionless gas: Numerical study - Aoki
 \, K (Kyoto)
DTSTART:20100907T080000Z
DTEND:20100907T090000Z
UID:TALK26062@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We investigate time-dependent behavior of a collisionless (or 
 highly rarefied) gas in the following two problems: \n\n(i) A collisionles
 s gas is confined in a closed domain bounded by a diffusely reflecting wal
 l with a uniform temperature. The approach of the gas to an equilibrium st
 ate at rest\, caused by the interaction of gas molecules with the wall\, i
 s investigated numerically. It is shown that the approach is slow and prop
 ortional to an inverse power of time. This is a joint work with T. Tsuji a
 nd F. Golse. \n\n(ii) An infinite plate without thickness is placed in a c
 ollisionless gas\, and an external force\, obeying Hooke's law\, is acting
  perpendicularly on the plate. If the plate is displaced perpendicularly f
 rom its equilibrium position and released\, then it starts an oscillatory 
 motion\, which decays as time goes on because of the drag exerted by the g
 as molecules. This unsteady motion is investigated numerically\, under the
  diffuse reflection condition\, with special interest in the manner of its
  decay. It is shown that the decay of the displacement of the plate is slo
 w and is in proportion to an inverse power of time. The result complements
  the existing mathematical study of a similar problem [S. Caprino\, et al.
 \, Math. Models. Meth. Appl. Sci. 17\, 1369 (2007)] in the case of non-osc
 illatory decay. This is a joint work with T. Tsuji. \n
LOCATION:Seminar Room 1\, Newton Institute
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