Experimental investigation of superstructures in turbulent liquid metal convection

在大展弦比范围内，对极低普朗特数流体湍流对流中的热上层结构进行了实验研究。实验将使用普朗特数Pr≈0.03的液态金属镓铟锡（GaInSn）进行。结合温度和速度测量将提供有关湍流、对流上层结构及其动力学的详细信息。一种新型的超声多普勒阵列技术将首次用于测量湍流液态金属对流中上部结构的二维速度矢量场。速度测量与多达100个测量位置的同时温度测量相辅相成，以实现热边界层温度分布的时空映射。将对局部位置的速度场和温度场进行高频采样，以获得湍流统计数据，而对超过上万个对流自由落体时间单位的长时间测量将揭示流型的长期动态。除此之外，我们将提供热量和动量输运的标量。提出的实验将为更深入地理解非常低普朗特数下的湍流上层结构以及它们在地球和天体物理流动以及工程系统中的主要相关性设定一个新的里程碑。

The appearance of thermal superstructures in turbulent convection within very low Prandtl number fluids will be investigated experimentally in a large aspect ratio domain. The experiments will be conducted using the liquid metal Gallium-Indium-Tin (GaInSn) that has a Prandtl number of Pr ≈ 0.03. Combined temperature and velocity measurements will provide detailed information about turbulent, convective superstructures and their dynamics. A novel Ultrasound-Doppler-Array technique will be used to measure for the first time two dimensional velocity vector fields of the superstructures in a turbulent liquid metal convection. The velocity measurements are complemented by simultaneous temperature measurements at up to 100 measuring positions to enable spatio-temporal mapping of the temperature distribution in the thermal boundary layer. High-frequency sampling of the velocity and temperature field at local positions will be performed to obtain turbulent statistics while long time measurements over ten thousands of convective freefall time units will reveal the long-term dynamics of the flow pattern. Besides that, we will provide scalings for the heat and momentum transport. The proposed experiments will set a new milestone for a deeper understanding of turbulent superstructures at very low Prandtl numbers with regard to their major relevance both in geo- and astrophysical flows as well as in engineering systems.