Vibration Characteristics Analysis Of Semi-submerged Ship

With the increasing development of international trade the world has not satisfied with the traditional small goods transportation and starts to develop semi-submerged ship which can carry large structure. Semi-submerged ship is a new type ship, can not only transport super large goods and industrial machinery but also lay submarine pipeline and be a casual wharf. Compare with other ship it has complex working cases and special structure. Because of large and irregular goods that semi-submerged ship carried it needs large cargo deck, so it has different principal dimension ratio with traditional ship. Otherwise, semi-submerged ship has special working condition; it has not only empty working condition and design working condition likes traditional ship but also has submergence working condition.The analysis of normal ship's vibration prediction is very common, and its theory and formula are full-blown. We used to calculate traditional ships'add mass water with Lewis method, but we must calculate semi-submerged ship's add mass water with fluid structure interaction numerical method for its special structure. In this paper I compile FORTRAN program by Source-sink method theory. First of all, I use the program to calculate an example to verify its accuracy and reliability then calculate a semi-submerged ship's vertical vibration add mass water weight. In this paper I use the whole ship three-dimensional FEM model to calculate the semi-submerged ship's vertical vibration frequency. Add the add mass water weight to the semi-submerged ship with changing component density method.This paper analyzes the semi-submerged ship type and development condition all around the world, and summarizes the hotspots and development direction of semi-submerged ship. Then introduce several popular add mass water weight theories, methods and suitable situation.Use Patran software build FEM modal of the semi-submerged ship, apply Lanczos method of Nastran software to calculate the ship's modes of global vertical vibration in several loading cases. Compare the ship's natural frequency in several loading cases to its main engine and propeller's excitation frequency, and draw the conclusion that vibration performance of this semi-submerged ship is acceptable. This paper has certain reference meaning to vibration prediction of semi-submerged ship.