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SUMMARY:Comparison between turbulent boundary layers and channels from dir
 ect numerical simulations - Jimenez\, J (Universidad Politecnica)
DTSTART:20080908T151000Z
DTEND:20080908T153000Z
UID:TALK13336@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Preliminary results are presented from a new simulation of the
  zero-pressure-gradient turbulent boundary layer at Re_	heta=1000-2100\, w
 hich are compared to simulations of turbulent channels at similar Reynolds
  numbers. Even the low order statistic differ considerably between the two
  flows\, including for some quantities the values within the buffer layer.
  In general the pressure and the transverse velocity fluctuations are stro
 nger in boundary layers than in channels\, even if the wall-parallel scale
 s that can be derived from the spectra and the two-point correlations are 
 simular in both cases. On the other hand\, the streamwise fluctuation inte
 nsities are roughly similar in both flows\, but their scales are shorter a
 nd narrower in boundary layers than in channels. \n\nThe difference betwee
 n the two flows is traced to an excess of production of the streamwise tur
 bulent energy in the outer part of the boundary layers compared to channel
 s (by a factor of order two)\, which is associated with the presence of a 
 stronger wake component of the mean velocity profile. Most of this excess 
 production is compensated by stronger pressure fluctuations and by the pre
 ssure-strain term\, whicht redistribute the energy to the transverse compo
 nents. The difference in the statistic can be traced in experimental resul
 ts at higher Reynolds numbers\, although qunatities such as the pressure f
 luctuations and the energy budgets are not available for them. These resul
 ts suggest that caution should be used in mixing different flows when docu
 ment\, for example\, Reynolds number effects in shear turbulence.\n
LOCATION:Seminar Room 1\, Newton Institute
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