# Scaled Model Simulation and Experimental Verification of Submarine Flexible Pipeline Laying System
## 4 Experiments and Analysis of Scale Model of Paved Tower
### Experimental Contents  
The experiment is mainly carried out for the state of the tower in pipeline laying. The experimental pipeline-laying angle is 90\({}^{\circ}\), and the axial tension generated by the pipeline is the tension generated by laying 10-inch pipeline in 3000 m water depth. For the sea conditions encountered during the laying process, the parameters, shown in Table 5, are selected, and the motion response parameters of the laying barges under the sea conditions parameters can be obtained by simulation in Section 2. The motion parameters of the hull are scaled and used for dynamic simulation of the scaled model to determine the maximum tension required for the scaled model tensioner support. By simulation, the max tensile load required for the tensioner support under each sea condition is shown in Table 6. The maximum load change with the sea condition is shown in Figure 22. Since the tensioner support is subjected to dynamic loads, which have a certain impact on the tower, 1.5 times the max dynamic loads under various sea conditions are used as the experimental loads. According to the analysis of the stress of various components during the operation of the scaled tower in Section 3, the dangerous area with maximum stress can be selected for measurement in the model experiment. There are four measurement points for selection. Because the tower is symmetrical, the points at its symmetrical position will not be measured repeatedly. The positions of these four measuring points have been marked in Figure 23. Point 1 and point 2 are located on the mounting side of the tower and mainly used to detect the stress of laying system when the tower is raised. Point 3 and point 4 are located on the Laying side of the tower, which are mainly used to analyze the stress of the laying system during pipeline laying. According to the above analysis and statistics, the actual measurement point position and tower operation status are shown in Table 7. Because the position of each measuring point is at the maximum stress, the posture of the tower and its mechanisms is different. Therefore, during the actual measurement, it is also necessary to adjust the tower to the corresponding working state and then measure the stress at the relevant points. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sea Condition Serial Number** & **Wave-to-Course Angle (\({}^{\circ}\))** & **Maximum Tension (N)** \\ \hline
1 & 0 & 26,700 \\
2 & 45 & 27,051 \\
3 & 90 & 27,608 \\
4 & 135 & 26,876 \\
5 & 180 & 26,361 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Maximum tension required for tensioner support under various sea conditions. Figure 21: Schematic diagram of scale model experimental system (**a**) and physical device (**b**). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sea Condition Serial Number** & **Significant Wave Height (m)** & **Wave-to-Course Angle (\({}^{\circ}\))** & **Wave Period (s)** \\ \hline
1 & 2.5 & 0 & 10 \\
2 & 2.5 & 45 & 10 \\
3 & 2.5 & 90 & 10 \\
4 & 2.5 & 135 & 10 \\
5 & 2.5 & 180 & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Experimental sea conditions. Figure 23: Location of measuring points on the mounting side of the tower (**a**) and the laying side of the tower (**b**). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Measuring Point** & **Position** & **Working Condition** \\ \hline \multirow{2}{*}{1} & Hinge between tower and upper connecting & \multirow{2}{*}{Tower vertical pipe-laying status} \\  & rod of tensioner support & \\
2 & Hinge between angle adjustment & \\  & mechanism and tower & \\
3 & At the bolt hole of the upper connecting rod & \\  & of the tensioner support & \\  & The hinge between the lower support part of & \\
4 & the tensioner support and the upper & \\  & connecting rod of the tensioner support & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Stress detection points of the scaled model. Figure 22: Maximum tension required for tensioner support under various sea conditions.