Steel flows into the mold through ports in the submerged entry nozzle, which is usually bifurcated.
The high velocities produce Reynolds numbers exceeding 100,000 and fully-turbulent behavior. Argon gas is injected into the nozzle to prevent clogging. The resulting bubbles provide buoyancy that greatly affects the flow pattern, both in the nozzle and in the mold. They also collect inclusions and may become entrapped in the solidifying shell, leading to serious surface defects in the final product. The jet leaving the nozzle flows across the mold and impinges against the shell solidifying at the narrow face.