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SUMMARY:Too much of a good thing? Destabilisation and mixing induced by st
 ratification in shear flows
DTSTART:20140527T140000
DTEND:20140527T150000
DTSTAMP:20261001T160915Z
UID:1c97b5a5581328be0879f46dba810752764bc582b8191986e68448db
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Colm-cille Caulfield\, BP Institute\, University of Cambrid
 ge\nBio : Dr Colm-cille Caulfield holds a joint appointment in the Departm
 ent of Applied Mathematics and Theoretical Physics and the BP Institute at
  the University of Cambridge. The BP Institute is a multi-disciplinary res
 earch centre devoted to fundamental studies of problems related to the ene
 rgy industry\, defined in the broadest sense. It brings together industria
 lists and academics with expertise in applied mathematics\, earth sciences
 \, engineering and chemistry.\nDr Caulfield is interested in working as pa
 rt of such diverse teams to study various fluid flows in the environment\,
  particularly in cases where density differences play a dynamical role. Of
  course\, density differences\, (due to temperature or composition variati
 on) are ubiquitous in the environment. Understanding the fundamental prope
 rties of the associated fluid dynamics is key to ensuring sustainable huma
 n activity. To name just three important examples\, understanding how dens
 ity differences affect fluid flows can allow strategies to be developed to
  model the climate system\, to deal with the dispersion of pollutants\, or
  to minimise energy consumption within buildings.\nAbstract : Statically s
 table fluids\, where the fluid density decreases monotonically with height
 \, are very common in the environment\, and arise due to the natural tende
 ncy for stationary fluid to be arranged in a state which minimises the pot
 ential energy of the system. It is then natural to suppose  that such a s
 tatically stable density distribution will reduce the growth rate and ulti
 mate nonlinear saturated amplitude of instabilities associated with some l
 arge scale vertical shear of the fluid\, compared to the properties of suc
 h instabilities in an unstratified fluid.  However\, stratification  not
  only can introduce  primary instabilities of stratified shear flows whic
 h do not arise in the absence of density variations\, but can also strongl
 y modify the secondary instabilities which subsequently develop\, modulati
 ng\, and in some circumstances significantly accelerating the transition t
 o turbulence. In this talk\, I will review some aspects of the present und
 erstanding of the destabilising effect of statically stable stratification
  in shear flows\, and discuss the central part such destabilisation plays 
 in the commonly observed non-monotonic dependence of turbulent mixing on o
 verall stratification\, leading\, through a classical physical mechanism f
 irst identified by Phillips\, to the inevitable development of layers in s
 tratified fluids.
LOCATION:ME B3 31 http://plan.epfl.ch/?zoom=19&recenter_y=5864112.19121&re
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STATUS:CONFIRMED
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