## 5 Results  
### Velocity Field Results  
For an operating point corresponding to a total flow rate of 2.2 L/min, the distributions of various flow parameters in the longitudinal section of TCPC systems are obtained. Figure 6 shows distribution of the flow velocity vector field obtained by the CFD simulation. The velocity vector field defines zones of local eddy flows. Figure 6A shows that the flow from the side of the inferior vena cava to the center inhibits the flow from the side of the superior vena cava, which inevitably leads to increased hydraulic losses. It can be seen in the Figure 6C diagram that the velocity value is less important, while the flow behavior is more uniform, due to this fact, the hydraulic losses of the TCPC system will be smaller. It should be noted that in TCPC-2 and TCPC-3 configurations, the stream is divided into two, practically not mixing with each other (Figure 6B,C). The results of the experimentally obtained distribution of velocity vector field are shown in Figure 7. The flow profile in the TCPC-1 coincides with the CFD modeling results. The flow from the inferior vena cava increases up to the center of the TCPC. Abruptly it stops due to the oncoming pressure of the fluid and is evenly distributed in the LPA and RPA. The fluid moving through the IVC is interfered with the flow from the SVC and spun counterclockwise to the LPA and clockwise to the RPA. Further, the flow is stabilized. TCPC-3 has the lowest mean density of the velocity vector field. Thus, this connection has the smallest hydraulic loss. Figure 8 shows the contour plot of the flow velocity modulus distribution obtained by the CFD simulation (A1-C1) and experimental data (A2-C2). The contour plot clearly shows areas where the flow reaches maximum speed and places where the speed values are minimal, this allows us to discuss the presence of the flow stagnation zones. Figure 6: Distribution of the flow velocity vector field obtained by the computational fluid dynamics (CFD) simulation. Velocity values for the color gradient are given in the sub picture. Flows from inferior and superior vena cava bump into each other that increases the hydraulic losses. Flows in TCPC-2 and TCPC-3 are divided into two parts, effectively decreasing hydraulic losses. Figure 7: Distribution of the flow velocity vector field obtained by experimental data. Flow profiles are similar to CFD results. TCPC-3 has the lowest mean density of the velocity. Figure 9 shows the contour plot of the static pressure distribution. The figure also shows the positions of the sections where the velocity profiles were built along a straight line perpendicular to the central axis of the tube. From the presented diagrams it can be observed that the greatest power losses take place in the TCPC-1 system (Figure 9A). It is shown that due to the incident flow of the inferior vena cava, the flow of the superior vena cava in the center is strongly inhibited and a region of increased pressure appears. In TCPC-2 (Figure 9B), the flow behavior from the inferior vena cava is similar to the case described above. It should be noted that the flow hits the wall of the pulmonary artery, as a result local pressure increases due to a decrease in the flow rate. In contrast, in the TCPC-3 system (Figure 9C), the pressure distribution is more uniform. Figure 8: The contour plot of the flow velocity modulus distribution obtained by CFD simulation (**A1,B1,C1**) and experimental data (**A2,B2,C2**). The contour plot shows areas where the flow reaches maximum speed and places where the speed values are minimal. In order to get a complete picture of the fluid flow in the TCPC models, data on the velocity distribution in the cross-sections was obtained. From the presented data (Figure 10) it can be observed that the experimentally obtained data is in good agreement with the CFD simulation data. In some cases, even repeating the curve shape. Cross-section L2 belongs to SVC and to a less degree corresponds to CFD simulation data. In this section, the flow is compressed closer to the center.