Interaction between a surface quasi-geostrophic buoyancy filament and an internal vortex
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This paper focuses on the nonlinear interaction between a surface quasi-geostrophic buoyancy filament and an internal vortex. We first revisit the stability of an isolated buoyancy filament. The buoyancy profile considered is continuous and leads to a continuous velocity field, albeit one with infinite shear just outside its edge. The stability properties of an isolated filament help to interpret the unsteady interaction with a sub-surface (internal) vortex studied next. We find that, in all cases, the filament breaks into billows, analogous in form to those occurring in Kelvin-Helmholtz shear instability. For intense buoyancy filaments, the vortex itself may undergo strong deformations, including being split into several pieces. Generally, the nonlinear interaction causes both the filament and the vortex to lose their respective ‘self’-energies to the energy of interaction. The flow evolution depends sensitively on whether the vertical vorticity of the filament and the vortex have the same or opposite signs — termed “cooperative” and “adverse” shear respectively. In cooperative shear, the filament rolls up into a coherent surface eddy above a vortex initially placed below it, whereas in adverse shear, buoyancy is expelled above the vortex. Although sufficiently great shear induced by the buoyancy filament may split the vortex in both cases, adverse shear is significantly more destructive.
Reinaud , J N , Dritschel , D G & Carton , X 2016 , ' Interaction between a surface quasi-geostrophic buoyancy filament and an internal vortex ' Geophysical and Astrophysical Fluid Dynamics , vol. 110 , no. 6 , pp. 461-490 . DOI: 10.1080/03091929.2016.1233331
Geophysical and Astrophysical Fluid Dynamics
© 2016, Informa UK Ltd. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at www.tandfonline.com / https://dx.doi.org/10.1080/03091929.2016.1233331
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