Study of transient flow and particle transport in continuous steel caster molds: Part I. Fluid flow

Abstract

Unsteady three-dimensional flow in the mold region of the liquid pool during continuous casting of steel slabs has been computed using realistic geometries starting from the submerged inlet nozzle. Three largeeddy simulations (LES) have been validated with measurements and used to compare results between full-pool and symmetric half-pool domains and between a full-scale water model and actual behavior in a thin-slab steel caster. First, time-dependent turbulent flow in the submerged nozzle is computed. The time-dependent velocities exiting the nozzle ports are then used as inlet conditions for the flow in the liquid pool. Complex time-varying flow structures are observed in the simulation results, in spite of the nominally steady casting conditions. Flow in the mold region is seen to switch between a "doubleroll" recirculation zone and a complex flow pattern with multiple vortices. The computed time-averaged flow pattern agrees well with measurements obtained by hot-wire anemometry and dye injection in fullscale water models. Full-pool simulations show asymmetries between the left and right sides of the flow, especially in the lower recirculation zone. These asymmetries, caused by interactions between two halves of the liquid pool, are not present in the half-pool simulation. This work also quantifies differences between flow in the water model and the corresponding steel caster. The top-surface liquid profile and fluctuations are predicted in both systems and agree favorably with measurements. The flow field in the water model is predicted to differ from that in the steel caster in having higher upward velocities in the lower-mold region and a more uniform top-surface liquid profile. A spectral analysis of the computed velocities shows characteristics similar to previous measurements. The flow results presented here are later used (in Part II of this article) to investigate the transport of inclusion particles.

Computational and experimental study of turbulent flow in a 0.4-scale water model of a continuous steel caster

“…The adequacy of this mesh refinement is demonstrated in separate investigations of the computational issues in LES modeling of continuous casting. [14,41] The time step (⌬t) is set to 0.0003 seconds to keep the simulation stable (CFL ϭ ⌬t max Ͻ 1: [42] here the CFL number was found to be ϳ0.6, so the results should be accurate). The computational time was 24 hours for 1 second of integration time on a Pentium IV 3.2 GHz PC (Linux 8.0, Redhat, Raleigh, NC).…”

“…However, the strong cross-stream flow is not seen when a stopper rod is used instead of a slide gate. [14] …”

“…Despite these differences, however, our recent studies have confirmed that the velocity field in a water model generally agrees with that in a steel caster, especially in the top region. [14] One of the advantages of a water model is that its transparent walls allow flow visualization such as dye injection [14,15] ( Figure 19) and the penetration of laser light. This enables the use of accurate and nonintrusive optical laser velocimetry techniques.…”

“…Recently, a few attempts have been made to apply it to the continuous casting process. [13,14,31] The principal idea of LES is that during the simulation, the time evolution of the large-scale (energy-containing) eddies is resolved and the small energy-dissipative eddies are "filtered." The filtering of the small eddies generates a residual stress tensor [20] in the Navier-Stokes momentum transport equation, which is included using a subgrid scale (SGS) model.…”

Modeling of Transient Two-Phase Flow in a Continuous Casting Mold Using Euler-Euler Large Eddy Simulation Scheme

“…The large eddy simulation (LES) was successfully applied to obtain the asymmetrically flow of molten steel in the single phase in the mold. [15][16][17][18] But there is no work published on studying the two-phase flow for argon gas-molten steel in mold using the LES.…”