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SUMMARY:How do waves create ‘sausages’\, ‘pancakes’ and ‘cannell
 onis’ from ‘spaghetti’ turbulence? - Avishek Ranjan\, CUED
DTSTART:20150213T130000Z
DTEND:20150213T140000Z
UID:TALK55603@talks.cam.ac.uk
CONTACT:Aleksandra Przydrozna
DESCRIPTION:I will describe how inertial waves can spontaneously create co
 lumnar flow structures from a localized layer of (a) freely decaying turbu
 lence (b) buoyant blobs (as an example of natural forced turbulence) under
  rapid rotation. These examples occur frequently in geophysical environmen
 t\, from the atmosphere-oceans to the core of the Earth. Energy iso-surfac
 es obtained from direct numerical simulation (DNS) in a periodic box show 
 that columnar structures emerge from turbulence and grow into the adjacent
  quiescent fluid. Helicity is used as a diagnostic and confirms that these
  structures are formed by low-frequency inertial waves and travel at their
  group speed. In particular\, it is observed that structures growing paral
 lel to the rotation axis have negative helicity and those moving anti-para
 llel to the axis have positive helicity\, a characteristic typical of iner
 tial waves. Moreover\, proper orthogonal decomposition (POD) can be effect
 ively used to study the dispersion pattern of these waves. In the presence
  of an imposed magnetic field perpendicular to rotation axis\, it is obser
 ved that the flow structures become elongated (anisotropic) along the dire
 ction of the field.
LOCATION:LR3B\, Inglis Building\, CUED.
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