# Dresden 2020 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 3: Fluid Physics of Turbulence

### DY 3.5: Vortrag

### Montag, 16. März 2020, 10:45–11:00, ZEU 118

The boundary zonal flow (BZF) in turbulent rotating convection — •Stephan Weiss^{1,7}, Xuan Zhang^{1}, Marcel Wedi^{1}, Dennis v. Gils^{2}, Robert E. Ecke^{3}, Lukas Zwirner^{1}, Guenter Ahlers^{4}, Susanne Horn^{5}, Eberhard Bodenschatz^{1,6}, and Olga Shishkina^{1} — ^{1}MPI for Dyn. and Self-Org., Göttingen, Germany — ^{2}Twente University, NL — ^{3}Los Alamos National Lab., USA — ^{4}UCSB, USA — ^{5}Coventry University, UK — ^{6}Georg-August University Göttingen, Germany — ^{7}Max Planck – University Twente Center

Thermal convection under the influence of rotation is one of the main driving forces for flows in astro- and geophysical systems. There, Coriolis forces are usually larger then centrifugal forces and vertical scales (i.e., in the direction of the rotation axis) increases compared to horizontal scales. Therefore, experiments are often conducted in cylinders of rather small aspect ratios (Γ=D/H) between their diameter (D) and height (H), as then the centrifugal forces remain small. We show by using experiments and DNS that in rotating thermal convection in a confined domain with no-slip boundaries, a large-scale flow structure (boundary zonal flow - BZF) develops at the lateral sidewalls, which reaches from the bottom to the top of the cell. In the BZF the vertical velocity and thus the heat transport is severely enhanced. The BZF is periodic in azimuthal direction with a wave number of twice the aspect ratio Γ. While the fluid moves in cyclonic direction close to the sidewall, the entire structure drifts in anticyclonic direction. The BZF is crucial for extrapolating experimental results onto natural systems and also plays an important role in many engineering applications.