Staircase formation in fingering convection
speaker: Francesco Paparella (Division of Sciences and Mathematics New York University Abu Dhabi)abstract: Fingering convection occurs when two buoyancy-changing scalars are strati- fied in such a way that the least-diffusing one, if taken alone, would produce an upward increase of density, but the most diffusing one reverses this tendency, making the density field to increase downwards. Set-ups of this sort are found in stellar physics, metallurgy, volcanology and, especially, oceanography, where the two scalars are temperature and salinity. Although both scalars flow down-gradient, this form of convection transports density up-gradient. The convective motions are sustained by small-scale struc- tures (the blobs) that displace vertically temperature and salinity anomalies, whose non–Gaussian distribution can be deduced from the equations of motion. When the convection is sufficiently vigorous, the blobs self-organize into clusters having enough size and kinetic energy to locally overturn the fluid. I will argue, by means of a simple model embodied by a system of partial differential equation in one spatial variable, that the appearance of clusters is responsible for the formation of staircases: kinked, step-like profiles of horizontally averaged density, temperature and salinity, that have long been observed in laboratory experiments and oceanographic measurements.
timetable:
Wed 7 Feb, 11:05 - 11:40, Aula Dini
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