Ultrasound instrumentation with adaptive beam shape for investigat-ing turbulent liquid metal flows
Investigating magnetically influenced flows in liquid metals and semiconductors is increasingly important for optimizing industrial processes as steel casting and photovoltaic silicon production. Especially the characterization of turbulent flows is highly relevant in that context. Turbulent flow behaviour can be described by two-point correlation functions, which are determined by measuring the velocity at two locations at the same time with a high spatial resolution for varying distances of those two points. At the moment no available flow instrumentation for liquid metals provides this measurement modality.
We developed a modular ultrasound research platform [1] to perform measurements using the ultrasound phased array principle. This allows a simultaneous velocity measurement at two different locations with high spatial resolution and enables the measurement of turbulence characteristics in liquid metal flows. This measurement system will be applied to a convection experiment (Rayleigh-Bénard convection) to answer fundamental question on the occurrence and onset of turbulent flow regimes. To investigate these transient and instationary flows, new signal processing techniques will be applied in this research project. Compressed sensing is used to decrease the measurement data rate and to increase the measurement time and temporal resolution. A coherence weighted beamformer and correlation based velocity estimation will be used to increase the spatial resolution.
Staff: C. Kupsch, R. Nauber
Period: 10/18 - 09/21
Partner: Helmholtz-Zentrum Dresden-Rossendorf, Dr. Eckert
Application of two independent sound fields to measure the two-point correlation in a flow. a) spatial f-correlation, b) spatial g-correlation, c) temporal correlation
[1] Mäder, K., Nauber, R., Galindo, V., Beyer, H., Büttner, L., Eckert, S., & Czarske, J. (2017). Phased array ultrasound system for planar flow mapping in liquid metals. IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 64(9), 1327-1335.