2.3.3. Mesh and Convergence

The computational mesh of the fluid domain was generated using the Body Sizing and Inflation tools, respectively. Body Sizing allows one to set the mesh item type and size. The Inflation tool allows one to thicken the mesh in the near-wall regions to further reveal the near-wall effects (Figure 1a). The computational mesh for the solid domain was selected based on the study of the mesh convergence of the results.

Five different element sizes were selected to analyze the sensitivity to the grid density (Table 1). The element types used in all grids were hexahedral and tetrahedral. An analysis of the sensitivity to the mesh density was carried out based on the achievement of a relative difference ε min P = 0.21%, ε min V = 0.84% of the variation of the maximum values of pressure and velocity in the aorta–shunt–pulmonary artery system. Figure 2 shows a convergence plot for von Mises stress. The results of the study showed that the values of the maximum stress values for a coarse mesh differ significantly from a thickened mesh. Thus, for subsequent calculations, a denser mesh with a side size of a triangular finite element h = 0.2 mm was used. *Materials* **2022**, *15*, x FOR PEER REVIEW 8 of 24

**Figure 2.** Maximum stress variations with respect to the number of mesh elements for solid domain: (**a**) mesh dependency tests for maximum von Mises stress, (**b**) mesh dependency tests for minimum von Mises stress, (**c**) maximum and minimum values for aorta, shunt, and pulmonary artery. **Figure 2.** Maximum stress variations with respect to the number of mesh elements for solid domain: (**a**) mesh dependency tests for maximum von Mises stress, (**b**) mesh dependency tests for minimum von Mises stress, (**c**) maximum and minimum values for aorta, shunt, and pulmonary artery.

the loading rate and geometric dimensions of the specimen. As a result of the experiment, the modulus of elasticity was determined for different specimens (Table 2). The elasticity modulus strongly depends on the diameter and thickness of the shunt: for a thickness over 0.5 mm, its value increases several times, and for a thickness less than 0.35 mm, it decreases strongly. The stress–strain curve for a shunt with a diameter of 4.5 mm, wall thickness of 0.35 mm, and length of 20 mm by a rupture test is shown in the Figure 3. The

**number E (MPa) Diameter, d (mm) Wall Thickness (mm)**

 7.41 4.32 0.34 9.8 3.4 0.4 10.3 4.5 0.35 11.1 5.5 0.48 43.5 5 0.53

load rate was 30 mm/min and the preload was 0.5 MPa.

**Table 2.** Parameters of samples used in the study.

*3.1. Results of the Experimental Study*

**3. Results**

**Sample** 


**Table 1.** Parameters of samples used in the study.
