Eur. Phys. J. Special Topics 220, 79-89 (2013)
https://doi.org/10.1140/epjst/e2013-01798-x

Regular Article

Optical velocity measurements of electrolytic boundary layer flows influenced by magnetic fields

¹ Faculty of Electrical and Computer Engineering, Laboratory for Measurement and Testing Techniques, Technische Universität Dresden, 01062 Dresden, Germany
² Institute for Fluid Mechanics, Chair of Magnetofluiddynamics, Measuring and Automation Technology, Technische Universität Dresden, 01062 Dresden, Germany
³ Institute for Complex Materials, IFW Dresden, PO 271106, 01171 Dresden, Germany
⁴ MHD Department, Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, PO 510119, 01314 Dresden, Germany

^a e-mail: Joerg.Koenig@tu-dresden.de
^b e-mail: Juergen.Czarske@tu-dresden.de

Received: 17 December 2012
Revised: 5 February 2013
Published online: 26 March 2013

Abstract

Magnetic fields are applied to electrically conducting fluids in order to influence electrochemical processes through the magnetohydrodynamic effect. Various phenomena, e.g. on electrodeposited metal layers, which can be attributed to forced convections were observed. To provide information about acting forces, the laser Doppler velocity profile sensor was applied to measure the transition layer of a Lorentz force influenced flow over a backward-facing step and the velocity boundary layer during copper deposition. With this sensor, the electrolyte convection within < 500 μm of the front of an electrode is measured with a spatial resolution down to 15 μm. The interaction of buoyancy, Lorentz and magnetic field gradient forces is studied by measuring the velocities down to 10 μm in front of the cathode. Inside the concentration boundary layer, complex electrolyte convection is induced, which varies not only in time but also in its structure, depending on the forces present and their influence over time. In inhomogeneous magnetic field configurations, the magnetic field gradient force dominates the velocity boundary layer at steady state and transports electrolyte toward regions of high magnetic gradients, where maximum deposit thicknesses are found. In this way, the measurements confirm the predicted influence of the magnetic field gradient force on the structuring of copper deposits.