# Numerical Simulation of Liquid Film Characteristics during Atomization of Aluminum Alloy Powder
## 3 Simulation Results and Discussion
### Liquid Film Characteristics with Disk Structure at Different Speeds
Therefore, in general, compared with the flat disk, the liquid film thickness on the spherical disk decreases more slowly and stably with the increase in the rotational speed. At the same time, it can be seen from Figure 16 that the average liquid film thickness on the spherical disk is thinner under the same working conditions. Moreover, the thickness difference in the liquid film on the two disk-shaped surfaces decreases from 4.2 \(\upmu\)m to 0.3 \(\upmu\)m as the rotational speed increases from 10,000 rpm to 60,000 rpm. In other words, the influence of the disk shape on the thickness of the liquid film becomes smaller when the rotational speed increases to a certain range, but the distribution uniformity and stability of the liquid film are still mainly affected by the atomizing disk shape. Figure 16: Average thickness of liquid film on the surface of flat disk and spherical disk at different rotational speeds. Figure 15: Curve of continuous liquid film boundary diameter of flat disk and spherical disk at different speeds. The above numerical simulation was used to systematically study the motion state of the liquid film on the surfaces of different disk shapes and the distribution characteristics of the liquid film on the surface of the rotating disk at different rotational speeds. However, the law by which the liquid film breaks and evolves into liquid droplets is still unclear. Therefore, the evolution process of molten metal atomization into droplets in the rotating disk is studied in this section. The geometric model and specific structural parameters of the simulation model used in this part of the research were further simplified on the basis of the previous model. In order to capture the whole process of the liquid film on the surface of the rotating disk, the liquid filaments formed by fracturing, and their further breakage into droplets, as well as to reduce the calculation amount, only the liquid injection port and atomization disk were retained in the model, and the atomization disk was selected as a flat disk with its diameter reduced to 50 mm. Other components were also simplified and omitted. In order to highlight the evolution law of atomization crushing, the atomization flow rate was increased and the inlet liquid flow rate was set to 5.0 m/s, while the atomization speed was reduced to 2000 rpm. By increasing the flow rate and reducing the speed, the liquid film on the surface of the atomization disk is made to become thicker and easier to capture. At the same time, the modified liquid material is selected as the research object, and its material performance parameters are shown in Table 3, exhibiting the characteristics of high viscosity and large surface tension. Thus, it is easier to form a liquid filament state during atomization. Under the condition of high viscosity, more regular changes, such as necking, fracture, and spheroidization, will occur, and the formation and evolution phenomenon will be more obvious. The simulation was divided into two parts, the small-angle fluid domain and the whole-circle fluid domain, in which we studied the evolution law of the single liquid filament and the whole disk liquid film spreading and splitting into liquid filaments and breaking into liquid droplets. The advantage of small-angle domain (angle 10\({}^{\circ}\)) calculation is that the grid is finer and the result is of higher precision. For the small-angle fluid domain (angle 10\({}^{\circ}\)) and the whole-circle fluid domain, we adopted the cutting body mesh; the mesh size was 1.2 mm, and the atomization disk, the inlet area, and the disk edge area were encrypted with a mesh size of 0.0625 mm. To accurately capture the air-liquid interface and particles, the number of meshes was 1.72 million and 32.69 million, respectively.