Abstract
The mixing phenomena in a six strand billet caster tundish have been studied by numerically solving the Navier-Stokes equations along with the species concentration equation in a boundary fitted coordinate system comprising the geometry of the tundish. The solution of the species concentration equation has been utilised to compute the mixed, dead, and plug volumes of the tundish under different flow conditions. The numerical procedure and solution algorithm have been verified first by comparing the numerically obtained residence time distribution with that of the experiments done for a single strand bare tundish in the literature. It has been observed that the ratio of mixed volume/dead volume for the six strand tundish has a maximum value for a particular position of the outlets measured from one of the tundish walls. At that particular position of the outlets (where mixing is best), an advanced pouring box (APB) is placed on the bottom of the tundish surrounding the incoming inlet jet and the height of the APB has been varied to observe the effect on mixing in the tundish. It has been observed that the ratio of mixed volume/dead volume increases further with the use of an APB and attains a peak value after which it decreases with an increase of the height of the APB, signifying the existence of an optimum APB height. At this optimum height of the APB, the shroud immersion depth was changed from 0 to 400 mm. It was also observed that there exists an optimum immersion depth of the shroud where the ratio of mixed volume/dead volume attains yet another peak signifying still better mixing. However, increasing the immersion depth to higher values spoils the mixing significantly.
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