Simulation of Slag Droplet Entrainment by Volume of Fluid and Lagrangian Particle Tracking Coupled Modeling

The slag droplet entrainment is a common phenomenon in steel refining processes, which may lead to inclusions and defects. In the multiphase flow system, the distinct interface and tiny blobs possess a wide range of spatial and temporal scales and make it hard to be simulated. In numerical methods, the volume of fluid (VOF) approach is appropriate for capturing the interface, but for the unresolvable tiny blobs, the Lagrangian particle tracking (LPT) is preferable. This work newly implements a bidirectional VOF-LPT transformation algorithm for developing a multiscale solver in OpenFOAM to simulate the slag droplet entrainment. The interIsoFoam solver is selected as the main solver to resolve the interface, and the resolution is improved with using the geometric reconstruction and the adaptive mesh refinement (AMR). For capturing tiny droplets, a connected component labeling (CCL) method is adopted for detecting discrete droplets in the VOF field, and then the VOF-to-LPT transition takes place for saving computational costs. Conversely, the LPT-to-VOF transformation for droplets touching the interface is also incorporated to achieve the bidirectional transition. The solver is first validated by a simple case, indicating that the two-way transition algorithm and the Eulerian-Lagrangian momentum coupling are accurate. Then the solver is applied to simulate the slag layer behavior for revealing the mechanisms of slag droplet formation and entrainment. Two main mechanisms of slag droplet formation are identified, and it is found that fewer discrete droplets are generated when the surface tension increases.