Novel ultrasound array measurement system for flow mapping of complex liquid metal flows

In magnetohydrodynamics, model experiments are commonly conducted to investigate the interaction between magnetic fields and electrically conductive fluids. The available flow instrumentation for opaque fluids usually lacks the ability to capture and visualize a velocity field in one shot. We present a multidimensional ultrasound array Doppler velocimeter that employs multiple line arrays of transducers and allows the resolution of small scale structures in complex flows. The system achieves a lateral resolution up to 3 mm, an axial resolution of approx. 1.4 mm and frame rates up to 30 Hz in metal melts at room temperature. A flexible sensor arrangement allows for various measurement configurations, e.g. four planes can be measured simultaneously with one velocity component, two planes with two components or two lines with three components. We present an experiment in a square-shaped container driven by a rotating magnetic field and results of a model experiment for continuous steel casting. The measurement system has proven to be a powerful tool for research in magnetohydrodynamics

Modular Ultrasound Array Doppler Velocimeter with FPGA-based Signal Processing for Real-time Flow Mapping in Liquid Metal

AbstractInvestigating the complex interaction of conductive fluids and magnetic fields is relevant for a variety of applications from basic research in magnetohydrodynamics (MHD) to modeling industrial processes involving metal melts, such as the crystal growth process in the photovoltaic industry. This enables targeted optimizations of the melt flow and allows to significantly increase the yield and energy efficiency of industrial processes. However, experimental studies in this field are often limited by the performance of flow instrumentation for opaque liquids. We present an ultrasound array Doppler velocimeter (UADV) for flow mapping in opaque liquids at room temperature. It is modular and flexible regarding its measurement configuration, for instance it allows capturing two velocity components in two planes (2d − 2c). It uses up to 9 linear arrays with a total element count of 225, driven in a parallelized time division multiplex (TDM) scheme. A FPGA-based signal pre-processing allows to handle the massive data bandwidth of typ. 1.2 GB/s and enables a continuous and near-realtime operation of the measurement system. The capabilities of the UADV system are demonstrated in a basic MHD research experiment with a metal melt (GaInSn) in a cubic container of (67mm)3. The flow induced by a rotating magnetic field is captured with a temporal resolution of 250ms for the horizontal and vertical central cross-section of the cube