## 3 Results and Discussion  
### Model Verification  
To validate the accuracy of the contact parameters and other relevant parameters in the DEM simulation, the model underwent verification before the simulation test. The experimental verification platform is shown in Figure 5, and the red dotted box is the screw type fertilizer distributor.. The conveying process of the worm-type distributor was captured by a camera to record the flow patterns and particle distribution. The instantaneous comparison between the test and simulation is presented in Figure 6, where each moment corresponds to different motion states of the particles. The comparison reveals that, under the same conditions, the particle flow forms and distributions in different sections of the test device were generally consistent with the simulation results. For further verification of the simulation model's accuracy, changes in the cumulative mass with time under 50 rpm were measured. In the simulation process, data were collected at intervals of 0.1 s, with the moment when fertilizer particles appeared at the Group bin set as 0 s and a total extraction time of 8 s. In the test process, changes in the electronic scale readings were recorded by a camera, and mass data were extracted based on the number of frames in the video. As shown in Figure 7, the simulation and test curves exhibit a good fit,  
Figure 4: Average velocity of particles in the Hindering section. Figure 3: Snapshots from a DEM showing the evolution of fertilizer particles’ flow during fertilization: (**a**) an initial state where the particles are filled in the hopper, (**b**) particles gradually being full inside hindering section, and (**c**) a steady state in which average velocity of particles is in dynamical equilibrium. The screw rotational speed is 50 rpm. worm-type distributor under a rotational speed of 50 rpm was conducted. As illustrated in Figure 8, significant changes in mass flows from the red zone (barrier zone) were observed as the distribution helix rotated through different phase angles. Analyzing the changes in the mass flow rate in the barrier zone revealed regular fluctuations over time, with the mean fluctuating around the upper and lower deviations (Figure 9). Therefore, the continuous rotation of the distributed spiral and periodic changes in the size of the opening between the spiral sleeves were identified as the main cause of the fluctuation of the flow in the obstacle area, which is consistent with [PERSON]'s findings [31]. Furthermore, [PERSON] proposed that flow fluctuation is not only related to the helical structure but also closely associated with the force chain of particle interaction, representing another key influencing factor of flow fluctuation [32]. In the dynamic conveying process, uneven contact forces were generated among particles under the influence of external loads and gravity, forming a transmission path contact network known as force chains [33]. Given the focus on normal stress in the worm-type distributor [34], the force chain analysis primarily concentrates on the normal contact force. The network distribution of normal contact forces among particles under different phase angles is depicted in Figure 10, in order to clarify the failure stage of the force chain, a black dotted line is circled in the diagram. It is important to note that each contact rod represents a connection at the contact point of particles, and its size is proportional to  
Figure 8: Transient simulation effects of different phase angles of screw rotation of the screw fertilizer feeder with screw. The screw rotational speed is 50 rpm. Figure 9: Variation in mass flow rate of particle with time. The screw rotational speed is 50 rpm. the normal contact force (red for large numerical values and blue for small numerical values). With the continuous growth of the phase angle, force chains in the black zone are continuously broken, influenced by gravity.