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DY: Fachverband Dynamik und Statistische Physik

DY 32: Poster: Active Matter, Soft Matter, Fluids

DY 32.29: Poster

Wednesday, March 20, 2024, 15:00–18:00, Poster C

A basic structure of 2D Boussinesq-Convection — •Lukas Moczarski and Wolf-Christian Müller — Plasma-Astrophysik, TU Berlin, Deutschland

In thermally driven turbulence, heat is mainly carried by buoyant structures, so called thermal plumes. We show that in DNS of 2D homogeneous Boussinesq-convection these plumes condensate on a characteristic scale, on which their mutual interaction induces a large-scale vorticity to the flow. This plume-induced vorticity is proposed as a basis for flow structuring. It is shown that the zero-vorticity level set takes shape as a grid of intersecting lines, whose structure changes slowly on the scale of the large-eddy buoyancy time. A Lagrangian tracer diffusion analysis indicates that the grid lines and their intersection points are paths of enhanced convective transport, whereas the centres of large-scale vortices in between them entrap tracers and lead to reduced transport. A subsequent investigation of the energy cascade in physical space, obtained by Gaussian filtering in spectral space, reveals a strong correlation of the cross-scale energy flux with the grid lines. We show that this is due to the (mis-)alignment of large-scale strain and small scales stress which is strongly modulated by the motion of individual thermal plumes on the grid.

Keywords: Coherent Structures; Convection; Turbulence; Simulation