## 3 Results and Discussions
### Influence of Scaffold Structure on Bone Tissue Repair Scaffolds and Modulation  
#### 3.2.1. Aperture Size  
Numerical simulations of S-0.4 and S-0.62 scaffolds were conducted at an inlet velocity of 1 mm/s, with all other parameters identical to the baseline setup. Pressure contour plots were generated and compared against the S-0.7 scaffold, yielding the results presented in Figure 11.  
From the pressure distribution comparison chart, it can be seen that the pressure distribution trend of stents with different aperture diameters is the same, decreasing layer by layer along the direction of inlet velocity. The smaller the pore diameter, the larger the pressure difference between the inlet and outlet, and the more drastic the change in pressure with the height of the stent. The pressure difference betwe  
Figure 11. Comparison of pressure distribution of S-0.4, S-0.62, and S-0.7 scaffolds. Figure 10. Frequency plot of WSS distribution for S-0.7 scaffold at different flow velocities. of the S-0.62 stent is 1.88 Pa, which is 1.6 times that of the inlet and outlet of the S-0.7 stent, and the pressure difference between the inlet and outlet of the S-0.4 stent is 10.48 Pa, which is 8.9 times that of the inlet and outlet of the S-0.7 stent. When the pore diameter is larger, the liquid molecules can pass through the pore more easily, and the flow resistance is smaller, while when the pore diameter is reduced, due to the viscous effect of the liquid, it makes the friction between the molecules inside the liquid and the shear force between the liquid and the wall increase, which leads to a greater resistance to flow, and therefore the pressure difference increases. The change in permeability and the change in porosity for the three types of scaffolds are plotted in Figure 12.  
It can be seen that the porosity of the square pore unit cell-type scaffolds varies linearly with the cell pore diameter; the permeability increases with the increase in the pore diameter, and the larger the pore diameter, the greater the rate of change in the permeability, indicating that the permeability is very sensitive to the change in the cell pore diameter. When the permeability is low, the mass transfer inside the scaffold is obstructed, which will affect the cell nutrient supply and metabolic waste discharge demand. The velocity vector of the S-0.4 scaffold at an inlet velocity of 1 mm/s is plotted in Figure 13.  
From the velocity vector diagram, it can be seen that the mainstream direction of the S-0.4-type stent is consistent with the flow direction at the inlet and runs through the whole stent along the \(Y\)-axis direction, with the most intense flow at the center of the pore in the \(Y\)-axis direction and very few velocity vectors in the \(X\)-axis direction and \(Z\)-axis direction and slow flow in the lateral direction. Compared with the S-0.7-type stent, the velocity distribution inside the S-0.4-type stent was more inhomogeneous. Due to the decrease in  
Figure 12: Permeability and porosity changes in S-0.4, S-0.62, and S-0.7 scaffolds. Figure 13: S-0.4 scaffold velocity vector map. pore diameter and the increase in wall thickness, the volume of the low-velocity flow zone between the pores on the side of the stent increased, and a large amount of non-permeable volume existed, which was unfavorable to the growth and development of cells. The frequency distribution of WSS at an inlet velocity of 1 mm/s was statistically plotted in Figure 14 for the S-0.4-type stent and the S-0.62-type stent. From the figure, it can be seen that the WSS distribution of square pore cell type scaffolds with different pore sizes are not uniform, and there is a frequency concentration phenomenon, with the largest proportion of the relatively lowest WSS region, and the WSS distribution trend of other values between groups is slightly different, which is due to the flow inhomogeneity. The WSS distribution trend of S-0.4 scaffolds is similar to that of S-0.7, and it is similar to that of S-0.62 scaffolds, which is a concave distribution.