Dynamics of a two-dimensional flow subject to steady electromagnetic forces

A novel experimental setup is presented to study the dynamics of a two-dimensional (2D) flow formed of an electrolyte subject to steady electromagnetic forcing. A thin layer of potassium hydroxide is poured into a square-base container with a strong magnetic field (\(\vec{B}\)) achieved by permanent neodymium magnets inserted underneath the base. The set of electrodes of alternating polarity distributed along the perimeter of the container generates currents (\(\vec{j}\)) in opposite directions. Coherent primary vortices of scales about 2 cm are thus generated by the \(\vec{j} \times \vec{B}\) force. We also show, and for the first time, that fluid motion is caused by the magnetic field gradient where the amplitude of \(\vec{B}\) is equal to zero. It leads to the generation of jets with size about that of the container, that is, 25 cm. The interaction between these gradB jets and the edge vortices leads to a final flow dominated by large-scale vortices resulting from the inverse cascade process that destroys the small-scale coherent structures on one hand and on the other modifies the initial scale and direction of the gradB jets.