Numerical investigation of particle motion at the steel—slag interface in continuous casting using VOF method and dynamic overset grids

The capillary interactions are prominent for a micro-sized particle at the steel—slag interface. In this study, the dynamics of a spherical particle interacting with the steel—slag interface is numerically investigated using the volume of fluid method in combination with the overset grid technique to account for particle motion. The simulations have shown the particle’s separation process at the interface and successfully captured the formation and continuous evolution of a meniscus in the course of particle motion. A sensitivity analysis on the effect of different physical parameters in the steel—slag—particle system is also conducted. The result indicates that the wettability of particle with the slag phase is the main factor affecting particle separation behavior (trapped at the interface or fully separated into slag). Higher interfacial tension of fluid interface and smaller particle size can speed up the particle motion but have less effect on the equilibrium position for particle staying at the interface. In comparison, particle density shows a minor influence when the motion is dominated by the capillary effect. By taking account of the effect of meniscus and capillary forces on a particle, this study provides a more accurate simulation of particle motion in the vicinity of the steel—slag interface and enables further investigation of more complex situations.

Numerical Simulation of ONRT Turning Motion in Regular Waves

Numerically simulating a ship with six-degrees-of-freedom response motions of an unsteady maneuver in a wave environment is very important in seakeeping characteristics of ship design. This paper presents the simulation studies of the turning motion in regular waves of the ONRT model. Numerical simulations were performed using viscous CFD code HUST-Ship to solve the RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations and dynamic overset grids designed for ship hydrodynamics. RANS equations are solved by the finite difference method (FDM) and PISO arithmetic. The level-set method is used to simulate the free surface flow. Before the turning circle simulation, a V&V study is conducted for the total towed resistance. The real propeller was replaced by a description body force method in the process of turning motion. The constant rate of the revolution was applied throughout the simulation. The rotation of the propeller corresponds to the self-propulsion point of the model speed. The control of rudders was controlled by the following autopilot. The maximum rudder rate was assigned to 35.0 [deg/s]. The ship was released when a wave crest is passing the midship. The study focused on the parameters of the trajectories for turning circle, roll, pitch, velocity, etc, it is helpful to judge the influence of the wave on the turning motion. The simulation results match well with test data from IIHR.

Numerical Simulation of Surface Ship Motion in Regular Head Waves

The motion of surface ship in wave environments is fully three-dimensional unsteady motion and includes complex coupling with hydrodynamic force and dynamic motion of the rigid body. This paper presents simulations of the KCS model with motions involve pitch and heave in regular head waves. Computations were performed with an in-house viscous CFD code to solve RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations and dynamic overset grids designed for ship hydrodynamics. RANS equations are solved by finite difference method and PISO arithmetic. Level-set method is used to simulate the free surface flow. The simulation geometry includes KCS hull and rudder under three conditions with three wave length and wave height combinations and two velocities (Fr = 0.26 and 0.33). Total resistance coefficient CT, heave motion z and pitch angle θ have been compared between CFD and EFD. Comparisons show that pitch and heave are much better predicted than the resistance. In the first section, simulations considered only 2 degrees of freedom (heave and pitch), for the second section, numerical simulation added the rolling motion to study the KCS in regular head waves. The second simulation cases were carried out with the same velocity and wave length and amplitude combination as the first cases. Comparisons of heave and pitch motion between 2DOF simulations and 3DOF simulations were presented in this paper. Results show the difference of heave motion z and pitch angle θ between the 2DOF and 3DOF-simulasions. In both cases the free surface were studied as an example of the flow generated by the ship pitching and heaving.

Multi-Physics Coupled FEM Method to Simulate the Formation of Crater-Like Taylor Cone in Electrospinning of Nanofibers

Crater-like Taylor cone electrospinning is a novel, simple, and powerful approach to mass produce nanofibers. The Taylor cone, crater-like liquid bump on the free liquid surface, in this electrospinning process plays a key role to produce multiple fluid jets which finally solidifies nanofibers. A multi-physics coupled FEM method was employed to simulate the dynamic formation process of crater-like Taylor Cone in crater-like electrospinning. A blended k−ω /k−ε model for turbulence and dynamic overset grids to resolve large amplitude motions were used to simulate two-dimensional uncompressed flow, which was described in axisymmetrical coordinates. The numerical calculation results were obtained by a computational fluid dynamics (CFD) method. The effect of gas flow on the formation of crater-like Taylor cone and the production of nanofibers were also discussed. The experiments were carried out to validate the numerical results. The Polyvinyl Alcohol (PVA)/ distilled water solution with 18wt% and the air pressures ranged varied from 4 to 50kPa were used in our experiments. The results showed that the numerical results were in good agreement with the experimental results. This work provides a deep understanding of the mechanisms of micro fluid jets production in electrospinning processes and two-phase flow in specific type of industrial equipment.