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SUMMARY:Scaling law of fractal-generated turbulence and its derivation fro
 m a new scaling group of the multi-point correlation equation - Oberlack\,
  M (Fachgebiet fr Strmungsdynamik)
DTSTART:20081001T133000Z
DTEND:20081001T140000Z
UID:TALK13852@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Investigating the multi-point correlation equations for the ve
 locity and pressure fluctuations in the limit of homogeneous turbulence a 
 new scaling symmetry has been discovered. Interesting enought this propert
 y is not shared with the Euler or Navier-Stokes equations from which the m
 ulti-point correlation equations have orginally emerged. This was first ob
 served for parallel wall-bounded shear flows (see Khujadze\, Oberlack 1994
 \, TCFD (18)) though there this property only holds true for the two-point
  equation. Hence\, in a strict sense there it is broken for higher order c
 orrelation equations. Presently using this extended set of symmetry groups
  a much wider class of invariant solutions or turbulent scaling laws is de
 rived for homogeneous turbulence. In particular\, we show that the experim
 entally observed specific scaling properties of fractal-generated turbulen
 ce (see Vassilicos etal.) fall into this new class of solutions. This is i
 n particular a constant integral and Taylor length scale downstream of the
  fractal grid and the exponential decay of the turbulent kinetic energy al
 ong the same axis. These particular properties can only be conceived from 
 multi-point equations using the new scaling symmetry since the two classic
 al scaling groups of space and time are broken for this specific case. Hen
 ce\, extended statistical scaling properties going beyond the Euler and Na
 vier-Stokes have been clearly observed in experiments for the first time.
LOCATION:Seminar Room 1\, Newton Institute
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