## 2 Materials and Methods
### Stacking Test
#### 2.3.3 Simulated Stacking Angle  
The box for the stacking test was three-dimensionally modeled and loaded into EDEM. During the simulation, the total weight of the Sesbania seed model was set to 0.3 kg, and the simulation duration was 3 s. The resulting simulated stacking angle was 47.64\({}^{\circ}\); this corresponds to a percentage error of 38.09%, in contrast to the physical stacking angle of 34.5\({}^{\circ}\). This discrepancy arises because the state of the particle pile is determined by both sliding friction and rolling friction [26], and the contact characteristic parameters of the Sesbania seeds in the model do not perfectly match the actual values. Specifically, the gaps between the spherical particles in the seed model increase the contact area during simulation, leading to deviations. Additionally, the surface of the seed plate used for measuring the contact parameters is relatively uneven, further contributing to errors relative to the measured results and the actual values. Therefore, the relative disparity  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Parameters** & **Numerical Value** \\ \hline \multirow{3}{*}{Sesbania seed} & Density (kg/m\({}^{3}\)) & \(1.154\times 10^{3}\) \\  & Poisson’s ratio & 0.449 \\  & Elastic modulus (Pa) & \(5.577\times 10^{7}\) \\ \hline \multirow{3}{*}{PMMA} & Density (kg/m\({}^{3}\)) & \(1.18\times 10^{3}\) \\  & Poisson’s ratio & 0.33 \\  & Shear modulus (Pa) & \(1.77\times 10^{8}\) \\ \hline \multirow{3}{*}{304 Stainless steel} & Density (kg/m\({}^{3}\)) & \(7.93\times 10^{3}\) \\  & Poisson’s ratio & 0.3 \\  & Shear modulus (Pa) & \(1.7\times 10^{11}\) \\ \hline \multirow{3}{*}{PLA} & Density (kg/m\({}^{3}\)) & \(1.11\times 10^{3}\) \\  & Poisson’s ratio & 0.3 \\  & Shear modulus (Pa) & \(2.2\times 10^{8}\) \\ \hline \multirow{3}{*}{6061 Aluminum alloy} & Density (kg/m\({}^{3}\)) & \(2.7\times 10^{3}\) \\  & Poisson’s ratio & 0.33 \\  & Shear modulus (Pa) & \(2.7\times 10^{9}\) \\ \hline \multirow{3}{*}{Sesbania seed–PMMA} & Coefficient of restitution & 0.376 \\  & Coefficient of static friction & 0.601 \\  & Coefficient of rolling friction & 0.211 \\ \hline \multirow{3}{*}{Sesbania seed–304 Stainless steel} & Coefficient of restitution & 0.474 \\  & Coefficient of static friction & 0.466 \\  & Coefficient of rolling friction & 0.222 \\ \hline \multirow{3}{*}{Sesbania seed–PLA} & Coefficient of restitution & 0.431 \\  & Coefficient of static friction & 0.498 \\  & Coefficient of rolling friction & 0.209 \\ \hline \multirow{3}{*}{Sesbania seed–6061 Aluminum alloy} & Coefficient of restitution & 0.544 \\  & Coefficient of static friction & 0.448 \\  & Coefficient of rolling friction & 0.207 \\ \hline \multirow{3}{*}{Sesbania seeds} & Coefficient of restitution & 0.161 \\  & Coefficient of static friction & 0.677 \\ \cline{1-1}  & Coefficient of rolling friction & 0.242 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Material parameters for the simulation.  
between the measured and simulated stacking angles should be employed as an indicator when calibrating the contact characteristic parameters of the Sesbania seeds.