## 4 Methodology
### Numerical Simulation and Result Analysis
#### 4.4.2 Simulation Analysis of Air Inlet Velocity  
The initial air velocity of the equipment is set to 10 m/s. However, it is found that this initial wind velocity is insufficient for effectively separating the film impurity mixture. Therefore, experiments are conducted with increased wind velocities of 12 m/s, 14 m/s, 16 m/s, and 18 m/s to analyze their impact on the internal pressure and the winnowing efficiency of the film stalk separation device. To assess the effects of varying the air inlet velocity on the pressure and velocity distribution within the cavity, cross-sections are selected at 100 mm intervals horizontally across the film stalk separation device. A total of 40 cross-sections are chosen, and average pressure and velocity values are calculated for each cross-section. These values are then plotted to visualize the data. Figure 11 depicts the variation of stress along the hole as the air inlet velocity changes, while Figure 12 illustrates the change of fluid velocity along the cavity under different air inlet velocities. The goal of the analysis is to determine how changing the air inlet velocity affects the cavity's internal flow field pressure and velocity distribution.  
The analysis of Figure 11 indicates that as the air inlet velocity increases, the value of the flow field pressure inside the cavity also increases. When the air inlet velocity exceeds 14 m/s, there is a significant increase in the flow field pressure within the hole. The excessive flow field pressure results in an unstable force increase in the horizontal direction of the model and is not conducive to the separation of film impurity devices.  
Figure 11: The change of interior flow fluid pressure along the cavity under different air inlet velocities.  
Figure 12: The change of fluid velocity along the cavity under different air inlet velocities.  
In summary, when the air inlet velocity is set at 14-16 m/s, the pressure of the flow field inside the model increases steadily. The change in the flow field pressure is relatively gentle, indicating that this range of air inlet velocities is more suitable for winnowing. It suggests that maintaining an air inlet velocity within this range would result in more effective film separation.  
According to the analysis of Figure 12, it is observed that in the initial wind velocity, the flow field velocity inside the model is relatively low, ranging from 2 to 2.6 m/s. This low flow field velocity hinders the efficient separation of materials. However, as the air inlet velocity increases, the flow field velocity inside the model also increases significantly. When the air inlet velocity exceeds 14 m/s, the airflow becomes capable of carrying animal material and residual film further forward. Nonetheless, if the airflow velocity is too high at the front end of the model, it results in a significant increase in the magnitude of change of the flow field pressure. This leads to an unstable flow field, which is not conducive to effective material separation. Furthermore, with excessive airflow velocity, the volatility of the airflow increases significantly, preventing the smooth conveyance of materials and residual film. On the other hand, when the inlet wind velocity is 14 m/s, the pressure in the cavity remains relatively stable with minimal fluctuations. This stability allows for smooth material conveyance within the system.  
In summary, the air inlet velocity of 14 m/s is considered more reasonable based on the experiments and measurements.