Ultrasound instrumentation with adaptive beam shape for investigating 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. Phased array ultrasound system for planar flow mapping in liquid metals, IEEE transactions on ultrasonics, ferroelectrics and frequency control, 64(9), 1327-1335.(2017)