Baroclinic critical layers in stratified and rotating flows by Patrick Huerre (LadHyX)

Duration: 1 hour 3 mins

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Baroclinic critical layers in stratified and rotating flows by Patrick Huerre (LadHyX)'s image

Description:	Talk given by Prof Patrick Huerre (LadHyX) at Department of Aeronautics, Imperial College, London, 22 February 2017, as part of the ICL Aerodynamics seminar series. The talk considers two separate problems: (i) stratified shear flows with background rotation; and (ii) global linear stability of buoyant jets and plumes as a function of the Richardson number Ri and density ratio S.


Created:	2017-03-17 12:51
Collection:	UKFN_ICL_Aerodynamics
Publisher:	University of Cambridge
Copyright:	Patrick Huerre
Language:	eng (English)
Keywords:	stratified flows; shear flows; rotating flows; stability; zombie vortices; baroclinic instability; buoyant jets; plumes; Strouhal number;


Abstract:	The seminar consists of two distinct parts : Stratified shear flows with background rotation give rise to the spontaneous replication of zombie vortices at singular baroclinic critical points. A large Reynolds number asymptotic analysis is presented, which regularizes the critical point singularity. The predicted cross-stream structure is shown to agree quantitatively with computed viscous eigenfunctions for plane Couette flow. The global linear stability of buoyant jets and plumes is studied as a function of the Richardson number Ri and density ratio S in the low Mach number approximation. Only the m = 0 axisymmetric mode is shown to become globally unstable. A satisfactory prediction of the Strouhal number of the self-sustained oscillations in helium jets is obtained over seven decades of Richardson numbers.

Abstract:

The seminar consists of two distinct parts : Stratified shear flows with background rotation give rise to the spontaneous replication of zombie vortices at singular baroclinic critical points. A large Reynolds number asymptotic analysis is presented, which regularizes the critical point singularity. The predicted cross-stream structure is shown to agree quantitatively with computed viscous eigenfunctions for plane Couette flow. The global linear stability of buoyant jets and plumes is studied as a function of the Richardson number Ri and density ratio S in the low Mach number approximation. Only the m = 0 axisymmetric mode is shown to become globally unstable. A satisfactory prediction of the Strouhal number of the self-sustained oscillations in helium jets is obtained over seven decades of Richardson numbers.

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