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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:A-priori quasilinear modeling and beyond - Greg Ch
ini (University of New Hampshire)
DTSTART;TZID=Europe/London:20220401T100000
DTEND;TZID=Europe/London:20220401T103000
UID:TALK171227AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/171227
DESCRIPTION:The quasilinear (QL) reduction\, in which nonlinea
rities among fluctuation fields are retained only
where they modify the evolution of the mean fields
\, has proven surprisingly effective in the descri
ption of both wall-bounded and free (geophysical)
turbulent shear flows. Although generally invoked
as a useful but ad hoc approximation\, the QL redu
ction can be justified asymptotically in the limit
of temporal scale separation between the mean and
fluctuating flow. Notably\, in the limit of large
Reynolds number\, certain classes of invariant so
lutions asymptotically satisfy a QL reduction of t
he Navier-Stokes equations known as the vortex-wav
e interaction (VWI) equations. We begin by introdu
cing a new class of these asymptotically-QL invari
ant solutions that reproduce the uniform-momentum-
zone/internal-shear-layer structure characterizing
the inertial domain of turbulent wall flows. Next
\, we show how the formal asymptotic analysis moti
vates the generalized quasilinear (GQL) reduction\
, which effects a homotopy from QL to fully nonlin
ear models and frequently yields a significant inc
rease in accuracy. Finally\, we introduce a new me
thod for time-integrating slow-fast (G)QL systems
that obviates the need to resolve the fast dynamic
s while also allowing fully nonlinear interactions
(associated with bursting behavior) to be reincor
porated intermittently when prompted by the dynami
cs.
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:
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