Detailed Simulation of Flow in Continuous Casting of Steel using K-ε, LES, and PIV

During the continuous casting of steel, transient flow events can be very important to the generation of quality problems. These transient phenomena can be computationally modeled using Large Eddy Simulation (LES) models while conventional K-ε models yield time-averaged results. Recently, Particle Image Velocimetry (PIV) has been applied to measure quantitatively the transient velocity fields in water models of this process. Results using all three methods compare favorably and give new insight into the flow phenomena. The slide gate creates a strong swirl at the outlet ports of the nozzle, which is also predicted using a K-ε model. The inlet swirl is seen to persist more than halfway across the mold, causing a characteristic staircase velocity vector pattern in the PIV measurements when viewed in a plane parallel to the wide faces. Flow across the top surface was found in PIV to contain periods of 5-10s when the velocities were three to four times their mean values. This is likely related to inlet conditions and is important to the shear entrainment of the liquid flux at the top surface and level fluctuations. In both LES and PIV, the upper roll structure evolves chaotically between a single large recirculation structure and a set of distinct vortices. The lower rolls in PIV are significantly asymmetric for very long periods of time (~ 1-hour) and go through a repeating sequence of features. One of these features involves a short circuit between the upward and downward flow in the lower roll, which is also seen in the simulation. This appears to be inherent to the turbulent nature of the flow and is likely important to inclusion particle and bubble entrapment.