Measurement of Flow and Structures through an Acoustic Multimode Waveguide based on Time Reversal

Ultrasound-based measurements are a key component for fundamental research in Magnetohy-drodynamics, as they allow spatially and temporally highly resolved flow and structure imaging in opaque liquids. Due to the temperature sensitivity of the transducers, experiments are usually limited to room temperature. An approach for
in-process measurements in hot melts is to separate the ultrasound transducers from the hot fluid through an acoustic waveguide, which holds a temperature gradient. Up to now, single-mode waveguides are used that exhibit a strong acoustical attenuation, which leads to a low signal quality. Furthermore they are mechanically complex and do
not allow for direct imaging. This research proposal aims at developing and investigating methods for ultrasound-based imaging through acoustical multimode waveguides that can transport the information of a complete image. Due to the complex sound
propagation, a scrambling of the image occurs, which has to be compensated for quantitative measurements. This project focuses on the system engineering aspects of ultrasound imaging through multimode waveguides. The Time Reversal Virtual Array is
investigated as method for compensating complex sound propagation based on the time reversal invariance, enabling novel ultrasound imaging. Strategies for system identification without access to the measurement volume under laboratory (ex situ) and field conditions (in situ) are to be investigated. The imaging of structures and flows
should be comprehensively characterized and qualified for the use in hot melts. This proposal investigates the possibilities and limitations of the new measurement system and aims at transferring the insights to fundamental research in Magnetohydrodynamics.

Staff:      A. Klass, R. Nauber

Period:  01/19 - 12/21

Partner: Helmholtz-Zentrum Dresden-Rossendorf, Dr. Eckert

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