Fluid that is sufficiently heated from below and cooled from above is known as Rayleighâ€“Bénard convection (RBC) and has been at the center of scientific inquiry for a long time [1]. RBC serves as a model system for buoyancy driven convection and can be found in numerous astrophysical, geophysical, atmospheric, and industrial processes.

A schematic of a cylindrical RBC cell is depicted in figure 1. When the temperature difference Δ between the plates is large enough, the fluid enclosed by the cylinder will start to transport heat by buoyancy induced convection in addition to conduction. The temperature difference can be expressed in non-dimensional form by the Rayleigh number *Ra* and is a measure of the system's driving strength. Likewise, the resulting heat flux that passes through the plates and the fluid can be expressed by the non-dimensional Nusselt number *Nu*. One important question is the dependence of *Nu(Ra)*.

A schematic of a cylindrical Rayleigh-Bénard convection (RBC) cell with diameter |

· Turbulent RBC and the ultimate-state transition

· Rotating RBC

· Moist turbulent convection

· Inclined layer convection

To experimentally investigate turbulent heat convection at high

*Ra*numbers our group features the Göttingen "U-Boot".

References

[1] G. Ahlers, S. Grossmann, and D. Lohse, Rev. Mod. Phys. **81**, 503 (2009)