Velocity Measurement Techniques for Liquid Metal Flows

Analysis and control of fluid flows, often subsidiary to industrial design issues, require measurements of the flow field. For classical transparent fluids such as water or gas a variety of well-developed techniques (laser Doppler and particle image velocimetry, Schlieren optics, interferometric techniques, etc.) have been established. In contrast, the situation regarding opaque liquids still lacks almost any commercial availability. Metallic and semiconductor melts often pose additional problems of high temperature and chemical aggressiveness, rendering any reliable determination of the flow field a challenging task. This review intends to summarise different approaches suitable for velocity measurements in liquid metal flows and to discuss perspectives, particularly in view of some recent developments (ultrasound, magnetic tomography). Focusing mainly on local velocity measurements, it is subsequently distinguished between invasive and non-invasive methods, leaving entirely aside the acquisition of temperature, pressure, and concentration, for which [1] may serve as a comprehensive reference.