Flow measurements in liquid metals by means of the ultrasonic Doppler method and local potential probes

Substantial research activities have been carried out at HZDR during the last 15 years on the development and qualification of various methods to measure the velocity field in liquid metal flows. In this paper we report on two complementary methods for measuring the local velocity. The potential difference probe is a local sensor which is immersed into the liquid. Such sensors are very effective for investigations of the turbulent fluctuations at a local point. However, the installation of the probe in the bulk of the liquid might disturb the flow to be measured. Ultrasonic techniques are non-invasive, but need a continuous path from the ultrasonic transducer to the liquid under investigation. The ultrasound Doppler method delivers instantaneous profiles of the local velocity. Experimental applications of these measuring techniques in diverse liquid metal flows under the influence of magnetic fields will be presented here showing the capabilities and limitations of both methods.