Direct numerical simulations of magnetic field effects on turbulent flow in a square duct

Magnetic fields are crucial in controlling flows in various physical processes of industrial significance. One such process is the continuous casting of steel, where different magnetic field configurations are used to control the turbulent flow of steel in the mold in order to minimize defects in the cast steel The present study has been undertaken to understand the effects of a magnetic field on mean velocities and turbulence parameters in turbulent molten metal flow through a square duct The,coupled Navier Stokes magnetohydrodynamic equations have been solved using a three-dimensional fractional-step numerical procedure. The Reynolds number was kept low in order to resolve all the scales in the flow without using a subgrid scale turbulence model. Computations were performed with three different grid resolutions, the finest grid having 8.4 x 10(6) cells. Because liquid metals have low magnetic Reynolds number, the induced magnetic field has been considered negligible and the electric potential method for magnetic field-flow coupling has been implemented. After validation of the computer code, computations of turbulent flow in a square duct with different Hartmann numbers were performed until complete laminanzation of the flow. The time-dependent and time-averaged nature of the flow has been examined through distribution of mean velocities, turbulent fluctuations, vorticity, and turbulent kinetic energy budgets. (C) 2010 American Institute of Physics: [doi:10.1063/1.3456724]