# Study on Local Vibration Control of the 100 m X-BOW Polar Exploration Cruise Ship
## 3 Results  
### The 100 m X-Bow Local Vibration Test  
In order to analyze the mode of the polar expedition cruise, a finite element model is established. The total length of the model is 104 m, the ship's width is 18 m, the waterline height is 5.1 m, and the weight of the ship is 4265 tons. A centralized mass point simulation device is used, with a coupling between the centralized mass point and the deck picking, and an increase in material density is used to simulate the distribution of additional mass. The added mass and the center of gravity of the model strictly follow the report of weight and center of gravity, as shown in Figure 4. The mesh size is mainly 400 \(\times\) 400 mm, the plate structure is quad 4 element and tria3 element, the beam structure is bar2 element, and the damping factor of the structure is 2% [1]. The 100 m X-BOW Polar Expedition Cruiser has twin propellers and twin rudders with a 3100 mm oar diameter and 80% rated working speed of 192 RPM; the main engine parameters are shown in Table 1. According to the literature [20], the main excitation forces of the ship are main engine excitation and propeller pulsation excitation, and the excitation spectrum is shown in Figure 5.  
The excitation in Figure 5 was loaded into the finite element model to obtain the vibration velocity of each cabin. Several typical regions were selected to compare the vibration response spectrum curve of the central node in these regions with the test value. The comparison curve is shown in Figure 6. It can be seen from the figure that the dominant frequency positions of the simulation curve and the test curve can correspond well, and the trend of the curves is basically the same. The effective value pair of vibration velocity is shown in Table 2. The area with the largest error is the sunshine deck on the seventh deck, which is 22%, but the difference is only 0.24 mm/s. According to the literature [21] and the literature [22], from the perspective of comfort, this error can be ignored, so the simulation results meet the engineering accuracy requirements. It shows that the 100 m X-Bow polar cruise ship modal can reflect the actual vibration characteristics of the hull. The reasons for this error mainly come from two aspects: (1) Dressing, outfitting, and interior components are omitted in the finite element model, such as the floating bottom plate and interior partition in the four-deck and passenger compartments, which affect the admittance of the transfer path to a certain extent; (2) In the actual measurement, the cruise ship is also affected by the excitation of wind and waves, pumps, steering engines, and fans. For example, the second deck-laundry room is affected by the air compressor in the adjacent cabin, so the error is relatively large compared with other areas.  
Figure 5: Main excitation spectrum diagram. (**a**) Propeller pulsating excitation; (**b**) Host excitation force.  
Figure 6: Comparison between simulation value and test value of vibration response. (**a**) Second deck–laundry room (DECK2); (**b**) Third deck–passenger compartment (DECK3); (**c**) Fourth deck–passenger compartment (DECK4); (**d**) Fifth deck–dining room (DECK5); (**e**) Sixth deck–passenger compartment (DECK6); (**f**) Seventh deck–sun deck (DECK7).