## 3 Results and Discussions
### Influence of Scaffold Structure on Bone Tissue Repair Scaffolds and Modulation
#### 3.2.3 Unit Cell Shapes  
Several sets of numerical simulations were performed to analyze the scaffolds with different cell shapes, which will be discussed in separate cases. Firstly, the pressure was analyzed. C-0.7 and C-0.8 differed only in pore size, which has been discussed in Section 3.2.1. Therefore, the pressure distribution plots of C-0.7, D-0.62, and Z-0.6 stents at an inlet velocity of 1 mm/s are compared here, as shown in Figure 19.  
Figure 18: WSS distribution of S-0.8-0.56 and S-1.2-0.84 scaffolds. At identical inlet velocities, scaffolds with different unit cell shapes exhibit highly similar pressure distributions, all decreasing from the upper to lower layers along the inlet flow direction. Surface integral calculations of inlet-outlet pressure differences yielded values of 1.8433 Pa (C-0.7), 1.0132 Pa (C-0.8), 1.9351 Pa (D-0.62), and 1.6386 Pa (Z-0.6), from which permeability values were calculated and compared against square-pore scaffolds in Figure 20.  
The six scaffolds have the same cell size, with differences in cell shape and pore size. C-0.8 and S-0.7 scaffolds have the same porosity, and C-0.8 scaffolds have a larger pore size and higher permeability. The pore size has a greater effect on the permeability than the cell shape for the same porosity. C-0.8 and S-0.7 scaffolds have the same pore size, and C-0.8 scaffolds have a larger pore size and higher permeability. Comparison of S-0.7 and C-0.7 stents shows that the square pore cell increases the permeability through higher porosity. Comparison of D-0.62, Z-0.6, and S-0.6 reveals that the stents with columnar cell structure have the largest porosity and the highest permeability when the pore sizes are the same, and the difference between the diamond-shaped pore stents and the square pore stents is not obvious in terms of porosity and permeability. It can be seen that for the cell-type scaffolds, the columnar cell is superior to the rhombic pore cell and the square pore cell from the perspective of increasing permeability, and the round pore cell is the least effective. In addition, the permeability of these six types of cells was higher than the value of human trabecular bone permeability (5.13 \(\times\) 10\({}^{-9}\) m\({}^{2}\)), and their overall mass transfer capacity met the demand of osteoblast growth and development. The flow vector in Figure 21 of the Z-0.6 scaffolds was plotted to analyze the effect of cell shape on flow within the scaffolds. Figure 19: Pressure distribution of C-0.7, D-0.62, and Z-0.6 scaffolds. Figure 20: Comparison of permeability of scaffolds with different cell shapes. Velocity vector fields indicate that columnar unit cell scaffolds exhibit axial flow dominance along the inlet direction (perpendicular to the XZ-plane), with peak velocities at XZ-plane pore centers and radial velocity decay toward pore walls. Z-0.6 scaffolds demonstrate superior internal flow homogeneity due to fluid-wall viscous coupling, where wall-adjacent fluid migrates laterally, enhancing inter-pore flow mixing and reducing flow stagnation zones. This uniform flow architecture creates favorable microenvironments for cell growth and differentiation. WSS contour plots for Z-0.6, D-0.62, and C-0.7 scaffolds are presented in Figure 22.  
The cylindrical structure of the Z-0.6 scaffold has the highest WSS in the region closest to the center of the main stream, decreasing radially in the direction away from the main stream, with an ellipsoidal WSS isosurface, and the lowest WSS in the region centered on the unit cell sidewall. The D-0.62 scaffold has high WSS regions distributed on walls close to the main stream, with the lowest WSS at the inter-unit-cell wall junctions. The C-0.7 scaffold exhibits a polarized WSS distribution, with higher WSS on mainstream-aligned walls and lower WSS on lateral pore walls. The transition zone between high and low WSS is indistinct.