The Turbulence Length Scale as A Criterion to Evaluate the Performances of Tundish Inhibitors to Float Non-Metallic Inclusions

Abstract

Five turbulence inhibitor (TI) designs are evaluated to define the highest performance to float non-metallic inclusions through the turbulence length scale analysis. The flow structures in the flow mushrooms, formed by the entry jet and its impact with a TI, generate coherent structures in the boundary layers’ walls of this device. The second invariant of the velocity gradient, Q, analyzes these structures. In the mushroom region, the inhibitor yielding the largest magnitudes of this second invariant has the most significant efficiency to float inclusions. Other criteria like the wall shear stress, the turbulent viscosity ratio, and the kinetic energy/friction velocity ratio are proved to be as valuable as the Q criterion to assess the performance of a given TI to float inclusions. This theory was tested numerically through the dynamics of amine particles in a tundish water model to simulate the dynamics of the non-metallic inclusions in steel and with amine powder injection experiments. The mass of powder escaping through the strand decreased as the absolute magnitudes of these criteria rose.