The deposition of metallic oxide inclusions (of about 10 µm in diameter) suspended in liquid steel is studied by numerical simulation. Two types of deposition surface are investigated, i.e., the liquid steel/solid wall interface and the liquid steel/liquid slag interface. In both cases, we focus on the boundary layer adjacent to the interface. The inclusion behavior is examined thanks to Lagrangian particle tracking: Newton’s second law governing inclusion motion includes the buoyancy force, the pressure gradient force, the added mass force and the steady drag force.For the liquid steel/solid wall interface, the inclusion behavior is analyzed in the buffer layer and in the viscous layer. These layers are described according to Ahmadi’s model, which provides a kinematic representation of the turbulent structures responsible for deposition, i.e., the sweeps and the bursts of liquid. The numerical simulations show that the deposition is mainly controlled by sedimentation. However, since the direct interception contribution increases with the turbulence intensity, direct interception becomes dominant for the highest values of the friction velocity (greater than 0.1 m.s-1). When the hydrodynamic interactions between the inclusions and the solid surface are taken into account, the deposition velocity is significantly reduced. Finally, it should be noted that the inertial forces have a negligible effect on the inclusion deposition velocity. For the liquid steel/liquid slag interface, the inclusion turbulent deposition is investigated using direct numerical simulation of the liquid flow combined with Lagrangian particle tracking under conditions of one-way coupling. The interface is modeled as a non-deformable free-slip surface. Unsheared turbulence is generated by random forcing in a finite-height region parallel to the free-slip surface. In between, the turbulence diffuses toward the free surface. The Reynolds number at the interface varies from 68 to 235. The inclusion diameter varies from 10-5m to 5.10-5m and the particle to liquid density ratio from 0.5 (alumina inclusions) to 1 (fictitious inclusions). It appears that the deposition of alumina inclusions is controlled by sedimentation whereas direct interception is the only deposition mechanism for non-buoyant inclusions. In the latter case, the deposition velocity strongly depends on the surface Reynolds number. It is shown that the deposition velocity made dimensionless by the free surface characteristic velocity scales as the inclusion diameter made dimensionless by the Kolmogorov length scale calculated at the free surface. When the hydrodynamic interactions between the inclusions and the free surface are taken into account, the direct interception contribution of the deposition velocity is significantly reduced (about half of the value without hydrodynamic retardation) but the scaling law is conserved.
