Convection

Thermal convection occurs in a great variety of circumstances. In the geophysical context, thermally driven flows are typically turbulent. Many aspects of turbulent convection are poorly understood. Turbulence in general is widely considered to be the most important unsolved problem of classical physics. In many respects we know more about the small scale structure of nuclear matter than about the structure of turbulent flows.

Geophysics is mostly interested in convection in a rotating fluid. Rotation organizes flows into columns aligned with the rotation axis. Convection rolls known from non-rotating Rayleigh-Benard convection cannot form. It is a matter of current research to find out which control parameters decide on whether rotating convection is strongly influenced by the Coriolis force or not. Shown below are isosurfaces of temperature computed numerically for rotating convection in a plane layer.



Convection also shows new behaviors if two distinct agents with different diffusivities determine the density of the convecting fluid, such as temperature and salinity of water. The problem of double diffusive convection has been studied mostly in oceanography, but it also appears in other areas of geophysics and astrophysics. A distinguishing feature of double diffusive convection is the formation of fingers, or long and thin channels in which flow is directed up- or downward. We use an electrochemical system to study double diffusive convection experimentally.