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SUMMARY:Transition to turbulence in a pipe - Mullin\, T (Manchester Centre
  for Nonlinear Dynamics)
DTSTART:20080911T084000Z
DTEND:20080911T090000Z
UID:TALK13368@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:The puzzle of why fluid motion along a pipe is observed to bec
 ome turbulent as the flow rate is increased remains the outstanding challe
 nge of hydrodynamic stability theory\, despite more than a century of rese
 arch. The issue is both of deep scientific and engineering interest since 
 most pipe flows are turbulent in practice even at modest flow rates. All t
 heoretical work indicates that the flow is linearly stable i.e. infinitesi
 mal disturbances decay as they propagate along the pipe and the flow will 
 remain laminar. Finite amplitude perturbations are responsible for trigger
 ing turbulence and these become more important as the non-dimensional flow
  rate\, the Reynolds number Re\, increases. Transition is generally abrupt
  and elucidating the details is difficult in practice. Here we report new 
 experimental results on the appearance of periodic states which arise belo
 w the transition threshold. They are in accord with recent numerical resul
 ts and their role in the transition process will be discussed.
LOCATION:Seminar Room 1\, Newton Institute
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