Turbulent convection in liquid metals at large Rayleigh numbers

采用室内实验和数值模拟相结合的方法，研究了极低普朗特数Pr=0.023时共晶镓铟锡（GaInSn）合金中的湍流对流。利用多个超声传感器布置的速度测量以及磁场层析成像的重建，首次揭示了瑞利数高达2e9的近壁区域和圆柱形对流单元体的速度场结构。这些测量将首次提供关于全球动量转移和三维大尺度结构长期行为的数据。他们得到了大规模平行谱元模拟的支持，重点是完整的三维边界层动力学以及加热和冷却板处非理想热边界条件对动量和传热的影响。模拟也将有助于解释测量到的湍流统计数据。这项联合研究为深入了解极低普朗特数下的湍流对流及其在地球和天体物理流动以及技术系统中的大量应用树立了新的里程碑。

Turbulent convection in an eutectic Gallium-Indium-Tin (GaInSn) alloy at a very low Prandtl number of Pr=0.023 is jointly studied in laboratory experiments and numerical simulations. For the first time, velocity measurements with arrangements of multiple ultrasound sensors as well as a reconstruction by means of magnetic field tomography will reveal the velocity field structure in the near-wall regions and in the bulk of the cylindrical convection cell for Rayleigh numbers up to 2e9. The measurements will provide for the first time data on the global momentum transfer and the long-time behavior of the 3d large-scale structure. They are backed up by massively parallel spectral element simulations with a focus to the full 3d boundary layer dynamics and the impact of non-ideal thermal boundary conditions at the heated and cooled plates on momentum and heat transfer. The simulations will also help to interpret the measured turbulence statistics. The joint investigations set a new milestone for a deeper understanding of turbulent convection at very low Prandtl numbers with its numerous applications in geo- and astrophysical flows as well as in technological systems.