MULTIMAG—A MULTIpurpose MAGnetic system for physical modelling in magnetohydrodynamics

Abstract Liquid metal model experiments (LMME) are an important tool in metallurgy and crystal growth. They allow investigating the flow structure and the transport properties in industrial facilities on a laboratory scale. Further, LMME provide a profound basis for the validation of numerical simulations. Physical modelling as well as up-scaling is ruled by similarity criteria. These depend, besides on the physical properties of the fluid, on geometry and, in the case of magnetohydrodynamics, on the attainable strengths of the magnetic fields. This paper describes the home-made MULTIpurpose MAGnetic field system, a facility composed of compact coil systems carrying high currents. Prominent features of MULTIMAG are (i) The large bore of 400 mm in height and 365 mm in diameter, which supports, in conjunction with the high current densities, the attainability of similarity criteria in the industrial range. (ii) Because the use of ferromagnetic material was strictly avoided in the construction, the rotating, travelling, pulsating, and DC in either homogeneous or cusp configuration magnetic fields may be superimposed linearly. (iii) In order to have as flexible as possible spatio-temporal distributions of the magnetic fields, the power supplies are realised as amplifiers. Each of the seven phases, three for the rotating and the travelling field, respectively, and one for the pulsating field, comprises a pulse width modulated power amplifier controlled by its own freely programmable frequency synthesizer. A detailed description of the facility is followed by some flow measurement examples demonstrating the performance of MULTIMAG.