Numerical study of the vibrational behavior hull surface vessel caused by propeller excitation

One of the most important issues in the design of a vessel structure is the vibrations of the structure and its effect on the comfort of the crew and the life of the equipment. The most important factor about the comfort of the crew in a vessel is the range of free and forced vibrations under various internal and external factors in the structure of the vessel. One of the serious factors in stimulation of vibrations in the hull vessel is the propeller. Excessive vibrations as well as the being the structure in the frequency range of propeller excitation, cause fatigue, components exhaustion, and also the resonance phenomenon. Resonance and vibration of the components are the structural design challenges, so in this paper, vibrations caused by a five-bladed propeller KP505 excitation were investigated using numerical simulation on a container vessel (KCS). First, the free vibrations of the hull vessel in wet mode were investigated. Then, to investigate the forced vibrations caused by the propeller excitation, the pressure distribution on the hull in self-propulsion mode was obtained from the numerical solution of the fluid flow by computational fluid dynamics. To validate the results, the natural frequencies obtained in free vibrations were compared with empirical formulas. Comparing the values of the first, second and, third bending frequencies with the empirical values, showed that the analysis error was 5.5, 26, and 26.6, respectively, which explain the accuracy of the analysis. Comparing the results of forced vibrations with the standard allowable range, it was shown that the vibrations are within the allowable range. Also, the structure has not being within the range of the excitation frequency of the propeller. As a result, the resonance phenomenon has not occurred.