Flow structure and heat transport in vertical convection at low Prandtl numbers (DFG VO 2332/4-1)

Through a cooperation of the HZDR and the Max-Planck Institute Göttingen (O. Shishkina, theoretical studies) a significant progress in the understanding of vertical thermal convection at very low Prandtl numbers and large Rayleigh numbers will be achieved. This type of convection has great relevance to industrial silicon crystal growth, in the solidification of metallic castings, the application of liquid metals to high temperature heat exchangers, and to absorbers of concentrated solar radiation in solar power plants. In addition, this category of thermal convection is important for understanding liquid metal planetary cores and stars. In the framework of the performed experimental and theoretical work, numerical models and simulations can be validated, respectively adapted and improved in critical and so far completely inaccessible parameter ranges. The Dresden experiments are performed with liquid gallium-indium-tin (GaInSn, Prandtl number Pr = 0.03) and provide information about the Rayleigh number dependent scaling of the global heat transport (Nusselt number, Nu) and the momentum transport (Reynolds number, Re). In addition, the measurements provide information on the flow field at high Rayleigh numbers, which is difficult to obtain with DNS at such low Prandtl numbers. The Göttingen DNS provides complete information on the velocity and temperature fields of the same Prandtl number, but at lower Rayleigh numbers than in the experiment. In addition to the goal of a global description of convection-driven flow processes, a recently developed analytical method of boundary layer modeling and scaling for the mean heat and momentum transport in laminar liquid metal flows will be extended to the case of fully developed turbulent convection flow of liquid metals.

Publications:
Zwirner, L., Emran, M. S., Schindler, F., Singh, S., Eckert, S., Vogt, T., & Shishkina, O. Dynamics and length scales in vertical convection of liquid metals. J. Fluid Mech. 932. (2022)