The thrust variation induced by the coupled vibration of torsional and axial propulsion shafting vibrations is one of the major excitations for the longitudinal deck house vibration of the container carrier. The conventional calculation method of thrust variation has been performed using 1D beam crank shaft model with lumped elements of equivalent stiffness and inertia. The calculation result of thrust variation using conventional method was higher than the measured one. In this study the direct frequency analysis method with the 3 dimensional FE model was used to calculate the thrust variation considering the coupling effects of both the crank throw and the propeller. The thrust variation was measured for the two(2) container carriers and three(3) crude oil carriers to confirm the proposed calculation method. The measurement system with the semiconductor sensors was installed at the intermediate shaft of the vessel. From the results of measurement and calculation it was found out that the calculated thrust variation with the proposed calculation method agreed well with the measured one. The advanced calculation method proposed in this study will be helpful to predict the accurate value of thrust variation at the design stage.
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