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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Turbulent heat transfer in wall-bounded flows - Ge
nta Kawahara (Osaka University)
DTSTART;TZID=Europe/London:20220106T130000
DTEND;TZID=Europe/London:20220106T140000
UID:TALK166429AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/166429
DESCRIPTION:If there is a difference in temperature between th
e bulk fluid and the wall surface in wall-bounded
turbulent flows\, such as thermal convection and s
hear flow\, heat will be transferred between the f
luid and the wall. This is (convection) heat trans
fer\, which is dominated by thermal conduction but
highly depends on flow characteristics. Turbulent
heat transfer is a significant problem not only i
n fluid mechanics but also in a wide variety of en
gineering applications.In the first part of this t
alk\, turbulent heat transfer in Rayleigh-Bé
\;nard convection will be reviewed\, with emphasis
on widely observed scaling properties\, i.e. the
classical scaling\, as well as the so-called ultim
ate scaling (corresponding to the Taylor dissipati
on law\, i.e. inertial energy dissipation) suggest
ed for extremely high Rayleigh numbers\, implying
that a wall heat flux is independent of thermal co
nductivity. Similarity and dissimilarity between h
eat and momentum transfer will also be reviewed fo
r wall-bounded turbulent shear flows\, in which th
e Taylor&rsquo\;s inertial dissipation does not ne
cessarily correspond to the ultimate heat transfer
.In the second part\, the feasibility of the ultim
ate heat transfer will be explored in turbulent Ra
yleigh-Bé\;nard convection and turbulent cha
nnel flow. Wall permeability\, which can be implem
ented on a porous wall\, is introduced in thermal
convection and shear flow. It is found that in bot
h thermal convection and shear flow between the pe
rmeable walls\, the ultimate heat transfer can be
achieved at high Rayleigh numbers and high Reynold
s numbers\, respectively. It will be demonstrated
why the wall permeability can lead to the ultimate
scaling in wall-bounded convective turbulence and
sheared turbulence.
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:
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