Phys.org  March 11, 2024
Researchers in Germany conducted an experiment inside a cylinder filled with the ternary alloy GaInSn focusing on the manifestation and dynamics of the large-scale circulation (LSC) in turbulent liquid metal convection. The large-scale flow structures were classified and characterized at Rayleigh numbers by means  enabling the full reconstruction of the three-dimensional flow structures in the entire convection cell. They identified the dominating modes of the turbulent convection. The analysis revealed that a single-roll structure of the LSC alternates in short succession with double-roll structures or a three-roll structure. This was accompanied by dramatic fluctuations of the Reynolds number, whose instantaneous values could deviate by more than 50 % from the time-average value. No coherent oscillations were observed, whereas a correlation analysis indicated a residual contribution of the torsion and sloshing modes. Analysis suggested  a stabilization of the single-roll LSC with increasing Ra at the expense of flow structures with multiple rolls. The relative lifetime of all identified flow states, measured in units of free-fall times, increased with rising Ra… read more. TECHNICAL ARTICLEÂ
The section through the experimental cylinder with magnetic field probes… Credit: B. Schröder/HZDR