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SUMMARY:Ring-Mode and McIntyre-Type Instabilities in Visco-Diffusive Swirl
 ing Flows: Isothermal and Non-Isothermal Couette–Taylor Annuli - Oleg Ki
 rillov\, Northumbria University
DTSTART:20260225T140000Z
DTEND:20260225T150000Z
UID:TALK243907@talks.cam.ac.uk
CONTACT:Anna Walczyk
DESCRIPTION:Swirling flows\, arising from the interaction of rotation and 
 shear\, are central to many engineering and geophysical systems\, ranging 
 from combustion to screw-type dynamos in magnetohydrodynamics. Even when R
 ayleigh-stable\, such flows can exhibit ring-mode instabilities\, first id
 entified by Leibovich and Stewartson in the aerodynamical context of trail
 ing vortices\, which are highly localised in radius and play an important 
 role in spiral-type vortex breakdown. Owing to their local character\, the
 se instabilities are naturally analysed using short-wavelength\, WKB-based
  methods such as the Lifschitz–Hameiri geometrical-optics approach. In t
 his talk\, I examine the stability of visco-thermodiffusive swirling flows
  in annular geometries with differentially rotating and differentially hea
 ted coaxial cylinders. Using a modified Lifschitz–Hameiri framework\, I 
 analyse localised ring modes in spiral Couette and spiral Poiseuille flows
 \, with and without a radial temperature gradient\, as well as in baroclin
 ic Couette flow. This allows the classical Leibovich–Stewartson criterio
 n to be extended to non-isothermal\, viscous\, thermally diffusive flows. 
 A central result is the discovery of a visco-diffusive oscillatory instabi
 lity of McIntyre type\, absent in the inviscid or isothermal limits. The r
 esults clarify how viscosity and thermal diffusion modify local instabilit
 y mechanisms in swirling flows and provide new insight into the dynamics o
 f non-isothermal Couette–Taylor systems.
LOCATION:LT6
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