# Numerical Simulation of Liquid Film Characteristics during Atomization of Aluminum Alloy Powder
## 3 Simulation Results and Discussion
### Comparative Analysis of Velocity and Pressure Distribution on Different Disk Surfaces
After this, under certain flow conditions, the thickness of the liquid film in the higher-pressure region will increase significantly to balance the change in momentum, resulting in the \"hydraulic jump\" phenomenon. The thickness distribution of the molten fluid film on the surface of the rotating disk is shown in Figure 7 [33]. In short, the change in pressure distribution in the center region of the rotating disk is attributed to the change in the liquid film caused by the hydraulic jump phenomenon. From the outer ring of the above area to the edge of the rotating disk, the pressure distributions on the surfaces of differently shaped disks reflect the different forces acting on the liquid film on the surfaces of the rotating disks, and these different forces lead to different motion characteristics of the liquid film on the surfaces of the different disks. The forces on the fluid micelles on differently shaped surfaces are shown in Figure 8. We define dF\(\alpha\) as the positive pressure perpendicular to the disk surface. It can be seen that the force on the fluid micelles on the surface of the spherical disk increases the positive pressure dF\(\alpha\) generated by the centrifugal force perpendicular to the disk surface, resulting in greater friction between the metal molten fluid film and the spherical disk surface, smaller sliding of the liquid film relative to the disk surface, and a more uniform spread and velocity distribution of the liquid film. Figure 5: (**a**) Velocity distribution cloud diagram of flat disk; (**b**) velocity distribution cloud diagram of spherical disk. Comparative Analysis of Liquid Film on Disk Surface and Breakage during Different Disk Atomization Processes  
Based on the VOF method, used to simulate the surface velocity and pressure distribution of the atomized molten metal in the spreading motion of flat and spherical plates, the VOF-DPM model was further used to simulate the surface spreading motion characteristics of different disk structures and the breakage law of the molten metal thin liquid film at 10,000 rpm. The liquid film spreading and breakage clouds in different disk atomization processes are shown in Figure 9. It can be seen that the aluminum alloy melt is poured into the center of the rotating disk through the guide nozzle at the central position, where the liquid film is formed. The liquid film diffuses along the radial direction and remains in the state of a continuous liquid film within a certain diameter, which is defined as the boundary diameter of the continuous liquid film. When the liquid film exceeds the critical boundary, the liquid film begins to split into liquid bundles. As is shown, the boundary diameter of the continuous liquid film on the flat disk is 32 mm under the condition of 10,000 rpm, and the boundary diameter of the continuous liquid film on the spherical disk is 45 mm, which indicates an increase equal to 13 mm compared with the flat disk. The liquid filaments produced by the splitting of the spherical disk in the splitting region are thinner and more numerous. Figure 8: The force diagram of fluid micelles on different disk-shaped surfaces. (**a**) Flat disk; (**b**) spherical disk. Figure 6: Pressure distribution cloud diagram in the atomization process of flat disk and spherical disk. (**a**) Flat disk; (**b**) spherical disk. Figure 7: Thickness distribution diagram of molten fluid film on the surface of rotating disk. According to further analysis of the simulation results, after the molten metal flows to the rotating disk, under the action of the friction and centrifugal force, the molten metal begins to move radially. In the process of motion, the speed of the liquid film gradually increases under the continuous action of the friction force and centrifugal force, and the thickness of the liquid film gradually decreases under the condition of a constant flow.