## 2 Materials and Methods  
### Structural Construction  
#### 2.1.1 Three-Dimensional Modeling Design  
1. Pre-Processing  
The current study is based on a regular-structured (cellular) scaffold that is frequently utilized in BTE studies. This scaffold is made up of several repeating cellular units that have apertures running through each surface of the cell to form flow channels inside the cell. The pores are connected, and the cells are arranged in a linear pattern that fits each other closely. This study employed SolidWorks 2021, a CAD software, to construct a three-dimensional (3D) model of the scaffold for bone tissue regeneration. Since the workstation can no longer perform calculations, the number of grid cells in the 5 cm \(\times\) 5 cm \(\times\) 5 cm model of the cellular structural bone tissue repair scaffold, which satisfies the minimum grid quality requirements, has surpassed 50 million, so the full structure of the scaffold was not simulated in this paper due to computer performance limitations. The Representative Volume Elements (RVE) method can be used to concentrate the numerical simulation's scope on one or more relatively small representative volume elements, which reduces computation time and the amount of computation because cell-structured scaffolds have a symmetric, cyclic structure. The results of pre-simulation of five simplified stent models with varying numbers of cells (composed of 3 \(\times\) 3 \(\times\) 5, 3 \(\times\) 3 \(\times\) 10, 5 \(\times\) 5 \(\times\) 5, 5 \(\times\) 5 \(\times\) 10, and 7 \(\times\) 7 \(\times\) 10 cells, respectively) demonstrated that the two simplified stents made up of 5 \(\times\) 5 \(\times\) 10 and 7 \(\times\) 7 \(\times\) 10 cells could meet the simulation requirements and could accurately respond to the necessary parameters (temperature, pressure, velocity, and WSS) of the trends, with a deviation of less than 0.05% between the two sets of simulation results. The numerical simulation experiments are conducted using a simplified scaffold consisting of 5 \(\times\) 5 \(\times\) 10 cells, taking into account the simulation experiments' efficiency. This study has so far established the structure of the scaffold for bone tissue restoration and created various pore diameters and pore distributions. The CAD geometric model of the scaffold with a square pore cell structure and the fluid domain is shown in Figure 1. Following geometric modeling completion, export files in STL or STEP (Standard for the Exchange of Product Model Data) format for import into ANSYS fluent 2021 R1 Workbench pre-processing. This study uses ANSYS Workbench (Wb), the project management platform of ANSYS. Wb integrates a variety of simulation software and modeling and data-processing tools, which can significantly improve work efficiency. In order to ensure the accuracy of the simulation results, structured grids are used for models with regular shapes, and tetrahedral meshes are generated using the patch conforming method for models with complex shapes, and mesh encryption is performed in local areas with complex shapes in order to ensure the quality of the mesh. Figure 2 shows some of the mesh models generated in this paper. 2. Fluent Solver Setup  
Confirm that the mesh quality in the cell mass, skewness, and orthogonal mass meet the requirements of the actual analysis of the experiment, and then define the model boundaries, including the flow inlet, flow outlet, different wall surfaces, and so on. Open Fluent, turn on the display mesh option, and check whether the inlet and outlet conditions and wall settings are read correctly and whether the model size is scaled.