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SUMMARY:Non-equilibrium turbulence scalings and self-similarity in turbule
 nt planar jets - Giaccchino Cafiero\, BP Institute
DTSTART:20180510T103000Z
DTEND:20180510T113000Z
UID:TALK104101@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:We study the self-similarity and dissipation scalings of a tur
 bulent planar jet and the\ntheoretically implied mean ow scalings. Unlike 
 turbulent wakes where such studies have\nalready been carried out (Dairay 
 et al.  2015\; Obligado et al.  2016)\, this is a boundary-\nfree turbulen
 t shear ow where the local Reynolds number increases with distance\nfrom i
 nlet. The Townsend-George theory revised by Dairay et al.  (2015) is appli
 ed to\nturbulent planar jets. Only a few proles need to be self-similar in
  this theory. The self-\nsimilarity of mean ow\, turbulence dissipation\, 
 turbulent kinetic energy and Reynolds\nstress proles is supported by our e
 xperimental results from 18 to at least 54 nozzle sizes\,\nthe furthermost
  location investigated in this work. Furthermore\, the non-equilibrium\ndi
 ssipation scaling found in turbulent wakes\, decaying grid-generated turbu
 lence\, various\ninstances of periodic turbulence and turbulent boundary l
 ayers (Vassilicos 2015\, Dairay\net al.  2015\, Goto & Vassilicos 2015\, N
 edic et al.  2017) is also observed in the present\nturbulent planar jet a
 nd in the turbulent planar jet of Antonia et al.  (1980). Given these\nobs
 ervations\, the theory implies new mean ow and jet width scalings which ar
 e found to\nbe consistent with our data and the data of Antonia et al.  (1
 980). In particular\, it implies\na hitherto unknown entrainment behaviour
 : the ratio of characteristic cross-stream to\ncentreline streamwise mean 
 ow velocities decays as the -1/3 power of streamwise distance\nin the regi
 on where the non-equilibrium dissipation scaling holds.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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