Electromagnetically generated vortex streets in a narrow channel

The understanding of fluid wakes is of fundamental importance in several technological applications. In this paper, we present an experimental and numerical study of vortex wakes produced by a traveling localized Lorentz force in a thin layer of electrolyte contained in a narrow channel. The experimental set up consists of an open rectangular container with two parallel electrodes placed along its longest walls and connected to a power source that supplies a uniform DC current to the fluid layer. A permanent magnet located underneath the container is moved with a constant velocity so that the interplay of the moving magnetic field and the applied transversal current generates a traveling Lorentz force that stirs the electrolyte and creates different vortex wakes according to the flow conditions. Attention is focused on the effect of lateral walls on the flow patterns, therefore, two containers of different width and magnets of different sizes were used to vary the blockage parameter. Numerical simulations using a quasi-two-dimensional model agree qualitatively with experimental visualizations. Further, flow transition maps built from experimental and numerical results are presented.