Nonsteady Behaviour of Free Surface Configuration and Velocity Distribution in a Flow Field of Molten Steel in a Mold

This paper treats numerical analyses of the flow structure of molten steel in a mold, focusing upon the unsteady behaviour of the free surface profile and velocity. These calculations were performed using the MAC-type solution method to solve a finite differencing approximation of the three-dimensional Navier-Stokes equations governing incompressible fluid flow. Here, the nonsteady body-fitted coordinate system was used so that the uppermost surface coordinate of the computational domain fits the free surface boundary in the physical space and therefore the mesh system is renewed at each computational time step. Also, the experimental study was undertaken to measure the surface velocity distribution, using water instead of molten steel. It was found that the numerical time-averaged surface velocity distribution is fairly in agreement with the experimental data. According to the results obtained by the present mathematical model, the flow field in a mold, including the free surface configuration and velocity, has been clarified to locally and temporarily fluctuate in somewhat a periodic manner. The effect of the casting speed and the kind of immersion nozzle on the flow structure of molten steel is estimated and discussed from a practical standpoint.