Finite element analysis of electromagnetic and fluid flow phenomena in rotary electromagnetic stirring of steel

摘要

This paper describes a fixed-grid methodology for the numerical simulation of electromagnetically driven flow in three-dimensional inductively stirred systems. It is based on a hybrid differential-integral formulation of the electromagnetic field to limit the finite difference/element solution of the electromagnetic field problem to the fluid flow domain. The electromagnetic field in the system was described using current vector potential (T) and reduced magnetic scalar potential (ψ) formulation of the field. The fluid flow problem was represented by turbulent Navier-Stokes equation. The governing equations were discretized using Galerkin method of weighted residual, and the discretized electromagnetic and fluid flow equations were solved simultaneously using an efficient finite element segregated algorithm. This new method was used to simulate sub-mold rotary electromagnetic stirring in continuous casting of steel. The computed results have shown that the electromagnetic force field generates a strong rotational flow within the vertical section covered by the stirrer, and a relatively strong secondary flow beyond the stirrer. It has also been shown that the rotational and secondary flows were driven primarily by the vorticity of the force field at the billet corners. The induced flow in the molten pool was found to be turbulent and the effective mixing region in the molten pool was about three times the length of the stirrer. The principal conclusion emerging form this work is that the secondary flow promotes mixing beyond the region confined by the stirrer, and the extent of mixing depends on the frequency of the applied rotating magnetic field.