# Model Test Research on the Propagation of Tsunamis and Their Interaction with Navigating Ships
## 5 Impact of Landslide-Induced Tsunamis on the Motion Characteristics of a Sailing Ship  
A ship's movement changes after the ship experiences a landslide-induced tsunami. The wave generated by a landslide differs from a general wave, and the occurrence of a landslide-induced tsunami involves a certain degree of abruptness. This study considers the characteristics of a ship's navigation speed in the region. The constant speed of the ship model is set to 0.4 m/s according to the scale ratio of the test model. The ship's characteristics in terms of roll and pitch are studied according to the rules for the construction and technical regulation for the statutory survey of a river vessel. Roll is, in fact, a lightly damped and lightly restored motion, and the roll natural period of a conventional ship is very close to the richest region in the wave energy spectrum. A very large amplitude of the roll motion can then occur, even in a moderate sea state, if the wave frequency spectrum is narrow and tuned with the ship's roll natural period. As shown in Figure 16, the ship's constant speed navigation route designed in this study is located at the bottom of the landslide point. That is, the most dangerous situation is that the same landslide volume produces a landslide-induced tsunami. Figure 16 demonstrates that at the initial moment, the landslide body begins to slide into the water at a high speed and the landslide body interacts with water. As the action time course continues, the sliding body enters the water to generate a landslide-induced tsunami, and the scattering propagation interacts with the ship. The effect eventually causes the ship's movement response amplitude to change. One second before the ship steadily sails in still water, the roll angle of the ship gradually increases after encountering a surge, and the roll angle reaches the maximum at 5 s. The ship's roll angle gradually decreases due to the effect of the restoring moment. During the entire voyage of the ship, the roll amplitudes increased dramatically due to the resonance effects when the incident wave period coincided with the free decay roll period of the ship. The maximum roll angle of the ship does not exceed 14\({}^{\circ}\), which is within a safe and reasonable range. During the ship's navigation, the ship is subjected to the impact of surge waves, which is superimposed on the other side of the ship after the reflection of the surge on the opposite shore. Therefore, when the amplitude of the roll motion of the ship changes, it is straightened by the reverse wave force: the angle then decreases. The response of the ship's roll motion is similar to the pitch motion response. It is interesting to note that the pitch amplitude begins to decline when the incident wave period is further increased. The amplitude of ship motion changes 1 s after the landslide, and the time of the pitch motion response reaches the maximum at 4.5 s. The pitch amplitudes increased sharply when the incident wave period  
Figure 15: Comparative results for different configurations. was close to the free decay pitch period of the ship. The maximum amplitude of the pitch response of the ship does not exceed \(2^{\circ}\), which is within a safe and reasonable range, as shown in Figure 17.  
In order to provide a better understanding of the yaw response to the incident waves, it is desirable to plot the maximal yaw angle. As shown in Figure 18, after the ship model enters the test region of the landslide water, the ship model goes into a state of unmanned steering. The direction of the ship's bow rapidly changes after encountering the effects of the landslide surge, and the direction of the ship's navigation is changed. Figure 18 shows that the ship is in a landslide. Two seconds before the wave, the ship rotates clockwise. With the continuous action of the landslide surge, the reflected wave from the opposite side acts on the other side of the ship. The ship's model is in a state of constant speed, and the port side of the ship is swelled.