# Investigation on Ship Hydroelastic Vibrational Responses in Waves
## 3 Hydroelastic Experiment Setup  
A self-propelled segmented model was designed and manufactured according to the target full-scale ship with broad bow flare. Table 1 presents the principal particulars of the ship model. Figure 2 shows the overview of the segmented model. The elastic model is divided into seven segments longitudinally, and sectional loads at the six cut sections are measured during experiments. A total of three steel backbones are used to connect the segments. The backbones are also made of Q235 steel, and therefore, have the same material parameters as those of the real ship hull beam. The heights and widths of these three steel backbones are iteratively adjusted to fulfil the requirements of the principle of similarity on the flexible characteristics for the purpose of reproducing the hydroelastic effect of the real ship. The first order natural frequency of vertical vibration of the ship model after the iteration process mentioned above is adjusted to be similar with that of the real ship. Figure 3 presents the arrangement of the three backbones. The three steel beams are fitted with strain gauges of 200 Hz sampling rate to measure the \(M_{BV}\) of the model at the cut sections. A propelling system, positioned at the stern region, is designed to reach the expected speed of the model in still water and waves.  
The tests were carried out in the ship model towing tank of Harbin Engineering University. The towing tank is 108 m long, 7 m wide, and 3.5 m deep. A towing carriage is used to serve as the platform where the monitoring apparatus such as the data acquisition system are placed. A computer controlled hydraulic driven wave generator, which is currently utilized as flap type, can generate both regular and irregular waves. The waves will be absorbed by a damping beach opposite to the wave  
\begin{table}
\begin{tabular}{c c} \hline Scale & 1:64 \\ \hline Displacement (kg) & 195 \\ \hline Length waterline (m) & 4.30 \\ \hline Length overall (m) & 4.85 \\ \hline Breadth (m) & 0.51 \\ \hline Designed Draft (m) & 0.12 \\ \hline \end{tabular}
\end{table}
Table 1: Main particulars of the model.  
Figure 2: Overview of the model setup.  
maker to prevent the effects of reflected waves on the generated incident waves and the ship model. A wave probe is positioned near the wave generator to monitor and record the generated waves at 50 Hz sampling rate. Table 2 gives the main parameters of the towing tank. Figure 4 shows the towing tank and the wave generator.  
Wave-induced heave and pitch motions of the model are monitored by an in-house designed, four-freedom motion recorder apparatus, which is installed on the towing carriage and connected to the ship model via two heave rods (see Figure 2). The two heave rods are jointly used to measure heave and pitch motions of the ship model while confine sway and yaw motions. The heave of the ship model at its CG can be derived by the two measured heave values at designated positions where the heave rods are installed. The pitch of the ship model is monitored by the inclinometer, which is fixed on the bottom of the heave rod. The sampling rate of motion is set to be 50 Hz during the experiment.