Vibration analysis of an underwater propeller blade for different core geometries

Underwater vibration may adversely affect life in the sea, or marine vessel comfort. To overcome these problems, it should be known the dynamic response of marine vessel parts like propellers. Vibration analysis of the marine propeller blade is very important to have information about its dynamic response. By this way, it can be learned how the blade behaves under different conditions like an underwater environment or rotation effect. The structures having cellular gradient core geometry can also exhibit better vibrational behavior. In the present study, the propeller blades having three different core geometries which are solid blade, honeycomb blade and anti-tetrachiral blade were designed via the SolidWorks program and analyzed via COMSOL Multiphysics program. The natural frequencies and mode shapes of each blade were obtained for both free condition and underwater environment condition. Then, both the two cases were compared with each other, and the three different blade models were compared within themselves. In addition, the frequency response functions of each blade were achieved to see if there is a resonance condition. The stress distribution on the blades was also inserted. As a result of this study, it is stated that there is no resonance condition as the working frequency (6.67 Hz) is far from the natural frequency of each blade. Furthermore, there is a frequency reduction at the rate of 30.5 percent, 32.7 percent and 35 percent for the solid blade, the honeycomb blade and the anti-tetrachiral blade, respectively, in the case of underwater rotating compared with free condition. The anti-tetrachiral blade has the lowest natural frequency in the underwater condition compared to the others and its frequency reduction ratio is closer to the study in the literature.