## 5 Effect of the Number of Model-Filled Particles on Simulation Accuracy
### Simulation Test of Wheat Gas-Solid Two-Phase Flow Coupling  
To further verify the effect of different filled particle numbers on simulation accuracy, a gas-solid two-phase flow coupling simulation test was conducted (Figure 6). The seed dispenser selected for the test used positive pressure airflow to press the seeds into the holes and complete seed filling so that its seed filling link could be analyzed. Due to the small size of wheat seeds, the number of seeds in the seed dispenser chamber was relatively dense, and the influence of particles on the airflow field must be considered in the simulation and analysis process. Therefore, the Eulerian two-way coupling model was used. Using three-dimensional software to establish the airflow field model of the seed dispenser and mesh division, the flow field grid volume was larger than the cohesive particle volume. Using the slip grid method, the shell's internal chamber grid area defaulted to static, and the planes in contact with each part were used as interfaces to complete the data exchange between the dynamic and static areas. To establish the link between the real and simulation tests, the leakage rate was adopted as an index between the tests. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Filled Particle Radius/mm** & **Wheat–Wheat Static Friction Coefficient** & **Wheat–Wheat Rolling Friction Coefficient** \\ \hline
0.2 & 0.0405 & 0.00866 \\
0.24 & 0.0486 & 0.00835 \\
0.28 & 0.0549 & 0.00812 \\
0.32 & 0.0568 & 0.00731 \\
0.36 & 0.0587 & 0.00715 \\
0.4 & 0.0598 & 0.00674 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Discrete elemental model results calibrated for physical property parameters by different filled particle radii. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Parameter** & \multicolumn{3}{c}{**Filled Particle Ball Radius/mm**} \\ \cline{2-7}  & **0.4** & **0.36** & **0.32** & **0.28** & **0.24** & **0.2** \\ \hline Y\({}_{1}\) & 0.312 & 0.341 & 0.354 & 0.362 & 0.397 & 0.398 \\ Relative error/\% & 3.95 & 3.19 & 2.33 & 2.41 & 2.26 & 2.19 \\ \hline Y\({}_{2}\) & 0.542 & 0.553 & 0.564 & 0.587 & 0.594 & 0.599 \\ Relative error/\% & 4.13 & 3.74 & 2.48 & 2.37 & 2.24 & 2.14 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Comparative analysis of simulation results for different filling models and actual test results. Considering the position of the type hole in the seed-filling area as the initial point, and the completely detached population as the termination point, we can delineate the seed-filling rate and judgment area. A camera is used to shoot during the seed discharg process, and leakage is judged as leaving the judgment area with no seed in the type hole [26]. The ratio of the number of leakage holes to the total number of holes is the leakage rate, which is calculated by the following formula:  
\[z=\frac{Z_{1}}{Z}\times 100\% \tag{5}\]  
where \(z\) is the leakage rate percentage; \(Z_{1}\) is the number of holes missed; \(Z\) is the total number of holes recorded. The real test waits for the seed discharger to work and stabilize before starting to record. However, due to limited computational resources, the simulation time is shorter. Two consecutive holes have seeds as a triggering condition. Therefore, the number of effective holes, leakage rate, and number of leakage holes are calculated in the same way as the real test. Jimai 22 varieties were selected as test samples, and the seed discharger was independently driven by an ECMA-C10401 ES servo motor with a torque of 0.3 N-m and speed of 3000 r/min. These parameters were accurately controlled to meet the test's high rotational speed requirements. The seed discharge disk speed was 800 r/min, with six holes, and three tests. Each test detection was no less than 1000 holes. The average value of the seed discharger's leakage rate was 8.24%. In the process of simulation and analysis, one must consider the effect of particles on the airflow field. Therefore, the Eulerian two-way coupling model and traction model selection of free flow models (Free-stream) were used.