Thermographic visualization of a flow instability in an electromagnetically driven electrolyte layer

Abstract

Visualization of complex flows is one of the most challenging problems in fluid dynamics. In this paper, we analyze experimentally the free surface swirling flow of a shallow layer of a weak electrolyte driven electromagnetically in a cylindrical container using a thermographic camera. The flow is produced by a force created by the interaction of a radial electric current and the vertical magnetic field of a permanent magnet. For given values of the applied current and fluid layer thickness, the azimuthal flow develops an instability that leads to the formation of long-lived, traveling anticyclonic vortices close to the walls of the container. Under isothermal conditions, a colorant is used to visualize the onset of the flow instability. Thermographic images provide evidence that the instability is also present under non-isothermal conditions and reveal the thermal effect of the vortices in the global flow. Our results encourage the use of non-intrusive electromagnetic and thermographic methods to explore complex phenomena in fluid dynamics and heat transfer.