Attenuation of Magnetohydrodynamic Oscillations in an Aluminum Reduction Cell Using Periodic Structures

Magnetohydrodynamic instability (MHD) in an aluminum reduction cell is due to the interactions between the conductive liquid currents and the magnetic field generated by very high currents flowing through current feeding circuit buses. Such phenomenon creates oscillations in this fluid, compromising the efficiency of the aluminum reduction process. The reduction cells consist, in their usual configuration, of a container with flat walls that accommodates the liquid. This work proposes a new geometry for the container based on periodic structures to mitigate such oscillations. The analysis of oscillations in fluid for both configurations is carried out with software developed to numerically simulate the process in two dimensions. The numerical formulation employs the finite-difference time-domain method to solve the Navier-Stokes equations explicitly through the Chorin projections method. The volume and surface of the fluid are mapped using the MAC method. The liquid is treated as incompressible and viscous, in addition to being electrically conductive. The accelerations caused by the magnetic field and the electric currents are coupled to Navier-Stokes by calculating the Lorentz Force. Results are analyzed by calculating differences between liquid heights obtained at rest and under applied electric currents.