31 May 2021 to 4 June 2021
Europe/Berlin timezone

Scaling of vertical mixing in two-species buoyancy-driven instabilities

31 May 2021, 10:40
15m
Oral Presentation (MS21) Non-linear effects in flow and transport through porous media MS21

Speaker

Anne De Wit (ULB)

Description

A miscible horizontal interface separating two solutions of different solutes
can deform into convective finger-like structures due to buoyancy-driven
instabilities like the classical Rayleigh-Taylor instability or the
double-diffusive instabilities, triggered by differential diffusion of the
solutes in the solutions. We analyse numerically for porous media flows the
scaling of the fingers vertical speed, defined as the slope of the temporal
evolution of the mixing length of the fingers. In the parameter space of the
problem, spanned by the buoyancy ratio R, and the ratio $\delta$ of diffusion
coefficients of the two species, the vertical speed is found to scale linearly
with the adverse density difference that drives the convective mixing in these
flows. The adverse density difference is the density jump across the spatial
domain where the density gradient of the diffusive base-state is negative along
the direction of gravity. It can be computed analytically from the diffusive
base-state density profile and can be significantly different from the initial
density difference when differential diffusion of the solutes are at play. Our
results evidence the possibility of controlling the nonlinear evolution of
mixing of buoyancy-driven instabilities in two-species stratifications

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Primary authors

Anne De Wit (ULB) Dr Shyam Sunder Gopalakrishnan (ULB) Prof. Bernard Knaepen (ULB)

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