Abstract

Fingering convection is a convective instability that occurs in fluids where two buoyancy-changing scalars with different diffusivities have a competing effect on density. The peculiarity of this form of convection is that, although the transport of each individual scalar occurs down-gradient, the net density transport is up-gradient. In a suitable range of non-dimensional parameters, solutions characterized by constant vertical gradients of the horizontally averaged fields may undergo a further instability, which results in the alter- nation of layers where density is roughly homogeneous with layers where there are steep vertical density gradients, a pattern known as “doubly-diffusive staircases”. This instability has been interpreted in terms of an effective negative diffusivity, but simplistic parameteri- zations based on this idea, obviously, lead to ill-posed equations. Here we propose a math- ematical model that describes the dynamics of the horizontally-averaged scalar fields and the staircase-forming instability. The model allows for unstable constant-gradient solutions, but it is free from the ultraviolet catastrophe that characterizes diffusive processes with a negative diffusivity.

Autore Pugliese

• Paparella Francesco

Tutti gli autori

• F. Paparella , J. von Hardenberg

Titolo volume/Rivista

ACTA APPLICANDAE MATHEMATICAE

Anno di pubblicazione

2014

ISSN

0167-8019

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

Ultimo Aggiornamento Citazioni

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Numero di citazioni Scopus

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Ultimo Aggiornamento Citazioni

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Settori ERC

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Codici ASJC

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