Thermal convection is one of the most important heat transport mechanism and as such plays a crucial role in many geo- and astrophysical systems. We study experimentally different aspects of thermal convection using the Rayleigh-Bénard (RB) setup, where a fluid layer of height L, is confined by a warm plate from below and a cold one from above.

A schematic of a cylindrical RB 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 D and length L. The warm bottom plate is at an excess temperature Δ with respect to the cold top plate at temperature T0. When the temperature difference Δ between the plates is large enough, the fluid enclosed by the cylinder will start to transport heat by convection in addition to conduction.


In our group we study several topics on heat convection. They involve:
  · Two-phase convection
  · Rotating RBC
  · Turbulent RBC and the ultimate-state transition
  · Non-Oberbeck Boussinesq 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)