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SUMMARY:Extrapolating turbulence to higher Re  - Professor Sergei Chernysh
 enko and Chi Zhang\, Imperial College\, London
DTSTART:20170210T130000Z
DTEND:20170210T140000Z
UID:TALK70381@talks.cam.ac.uk
CONTACT:Akshath Sharma
DESCRIPTION:In many practical applications\, the Reynolds number Re is muc
 h greater than the largest Re that can be achieved in direct numerical sim
 ulations and wind-tunnel experiments. Hence\, to apply the turbulence-rela
 ted results obtained in a wind tunnels or with computers\, extrapolation t
 o higher Re is needed. For the part of the flow very close to the wall suc
 h extrapolation is usually based on the classical universality hypothesis 
 stating that near the wall the turbulent flow parameters\, expressed in so
 -called wall units\, are independent of Re. However\, in recent years it w
 as established that the large-scale structures residing further away from 
 the wall affect the near-wall turbulence. Since these structures\, if expr
 essed in wall units\, are not Re-independent\, the classical universality 
 hypothesis is not correct. Moreover\, recent data indicate that as Re incr
 eases the outer large-scale structures become stronger. An outline will be
  given of the new technique for extrapolating statistical characteristics 
 of near-wall turbulence from medium to higher Re\, based on the recently d
 eveloped quasi-steady quasi-homogeneous (QSQH) theory. The QSQH theory is 
 an alternative to the classical universality hypothesis. The QSQH theory p
 rovided relationships between many turbulence parameters previously though
 t to be unrelated\, including for example those entering the well-known em
 pirical formula for the modulation of near-wall turbulence by outer struct
 ures\, and threw a new light on the Re-dependence of the logarithmic law c
 onstants. First results on extrapolating turbulence statistics to higher R
 e will also be presented. \n\n
LOCATION:JDB Seminar Room\, CUED
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