# Analysis of Feed Inlet and Optimal Feeding Amount of Waste Ground Film Impurity Removal Equipment
## 2 Materials and Methods
### CFD-DEM Fluid-Solid Coupling Simulation Analysis
#### 2.2.2 Fluid-Solid Coupling Simulation  
Further, we investigated the maximum collision force inside the tremmel screen, that is, determined where the maximum relative collision velocity occurred. The operation of the membrane miscellaneous wind separator was simulated using a combination of EDEM 2020 and Fluent 18.2 software. Pre-Processing of Fluid-Solid Coupling Simulation  
SolidWorks 2018 3D modeling software was used to model the structure of the membrane miscellaneous wind separator. Flow field simulation as well as the discrete element simulation model were also used to establish the model. The simplified flow field simulation model was imported into ICAM 18.2 software for mesh drawing. The rotating tremmel screen of the film miscible wind separator was located inside the stationary sealing hood; thus, the two fluid domains were plotted separately when the mesh was drawn. The screen holes on the tremmel screen were named interface surfaces. Data exchange between the two fluid domains was realized, and the delineated mesh model was imported into Fluent 18.2 software. The standard k-\(\varepsilon\) model was selected for computations, and the SIMPLEC algorithm was used for solving equations. The internal flow field of the film-hybrid wind separator was simulated, and the simulation results were exported to a.cgns format file. The results of the DEM model and the flow field simulation, data identified using an API function, were imported into the EDEM 2020 software. The operating parameters of each structure of the film miscellaneous wind separator were set separately to ensure that the coupled simulation results were consistent with the test results, and that the bench test material was followed. A three-dimensional model of residual film, straw, and soil particles was established. Parameters for material contact and physical characteristics were obtained using the drainage method via tensile tests with a mass spectrometer, a mechanical testing machine, friction and wear tests, and a literature review [16; 17; 18; 19; 20; 21]. The intrinsic parameters of the materials are shown in Table 1. \begin{table}
\begin{tabular}{c c c} \hline
**Materials** & **Intrinsic Parameters** & **Value** \\ \hline \multirow{4}{*}{Residual film} & Dimensions (length \(\times\) width \(\times\) thickness)/mm \(\times\) mm \(\times\) mm & \(100\times 30\times 0.1\) \\  & Poisson’s ratio & \(0.23\) \\  & Shear modulus/Pa & \(1.2\times 10^{6}\) \\  & Density/kg/m\({}^{3}\) & \(104\) \\ \hline \multirow{4}{*}{Straw} & Dimensions (diameter \(\times\) length)/mm \(\times\) mm & \(8\times 80\) \\  & Poisson’s ratio & \(0.35\) \\  & Shear modulus/Pa & \(1.37\times 10^{8}\) \\  & Density/kg/m\({}^{3}\) & \(257.8\) \\ \hline \multirow{4}{*}{Soil} & Equivalent particle size/mm & \(2\) \\  & Poisson’s ratio & \(0.4\) \\ \cline{1-1}  & Shear modulus/Pa & \(1.6\times 10^{8}\) \\ \cline{1-1}  & Density/kg/m\({}^{3}\) & \(1430\) \\ \hline \end{tabular}
\end{table} 
Table 1: Intrinsic parameters of the materials. The corresponding material intrinsic parameters were set in the Creator parameter setting interface in EDEM 2020. A particle model of residual film, straw, and soil was established, as shown in Figure 7. The Bonding V2 contact model was added to simulate the flexible characteristics of the residual film. The residual film particle arrangement law and the deformation of the residual film particles after the force are shown in Figure 7a,b. The model could represent the formation of flexible bonds between two bonded spherical particles. The flexible characteristics of the residual film were restored to their maximum extent. Since the volume fraction of the residual film inside the device was small, the effect of the thickness of the residual film on the flow field and the motion of the residual film was ignored to minimize computational efficiency.