Ultrasound Image Velocimetry with Adaptive Beamforming for Modal Measurements in Liquid Metal Convection

Coherent plane wave compounding allows to enhance the spatial resolution by maintaining high frame rates. Furthermore, by means of a phased array probe with adaptive beamforming, the imaging plane can be extended to the sides of the probe, although using a flat array. This approach is adapted and demonstrated for observing liquid metal convection in magnetohydrodynamic (MHD) model experiments, where high penetration depths of up to 200 mm are required, the access is limited due to the experimental conditions and the decomposition of oscillation modes requires sufficient spatial and temporal resolution. As a result of adapting ultrafast Ultrasound Imaging Velocimetry in this paper, a two component flow regime can be obtained in the conducted model experiment for penetration dephts of up to 100 mm with a spatial resolution of 2.7 mm and a temporal resolution of 2 Hz. The full penetration depth of 200 mm can be obtained with axial velocities only and a reduced spatial and temporal resolution. This allows a planar observation of turbulent and oscillating flow patterns in MHD convection experiments without elaborate fluid simulations.