Contactless inductive flow tomography for a thermally driven convection problem

The contactless inductive flow tomography (CIFT) allows to visualize the mean flow structure in liquid metals by measuring the flow induced magnetic field perturbations under the influence of one, or several, applied magnetic fields. The reliable measurement of these very small field changes, and the involved mathematics to solve the inverse problem, are the main challenges for this flow diagnostic method. We present preliminary results of CIFT applied to a thermally driven flow within a setup showing some similarity to Czochralski silicon crystal growth. As working fluid GaInSn was used. Due to the low velocities in the order of 1 cm/s, the dynamic range of the measurement system has to be enhanced to 5 orders of magnitude which set high demands on the stability of the installation and the current source. Large efforts were made to adapt CIFT to the experimental setup in order to compensate thermal expansion during the measurement. Typical features of the thermally driven turbulent flow could be detected in the magnetic field measurements and were verified by simultaneous temperature measurements recorded by thermocouples placed in the vicinity of the rim of the heat sink.