Study On Modeling Method Of Ship Vibration

In the process of operating, the ships will be inevitably affected by engine, propeller, waves and so on. The role of these external incentives will lead to different degrees of the ship vibration even harmful vibration. These excessive vibration may lead to fatigue damage, influencing work efficiency and even physical health, but will also affect the equipment's normal using. Therefore, in the stage of ship designing, we must predict the inherent vibration characteristics of the ship structure accurately to avoid resonance.The ship structure requires vibration calculation in the design stage. It is necessary for this vibration calculation to seek one calculational model which can improve the accuracy and simplify the calculation to meet the requirements of practical engineering in order to improve the accuracy of vibration forecasting. This paper studies modeling method of the equipments on ship and superstructure's overall vibration, then discuss the modeling method of the ship's overall vibration. We use the lumped mass element, plate element and assembled staff-lumped mass elements to simulate the equipment of ship. Based on computation and comparison of several common models, a new practical model is presented. The numerical result shows that the new model is precise and feasible and it is valuable for ocean engineering structure. As to the modeling of the superstructure's overall vibration, we discuss the influence of different model, boundary conditions, additional water mass and loading conditions on the natural frequency of superstructure. Taking the 8000TEU super container ships, 110000t oil tankers, 174000t bulk carriers, 76000t oil tankers, 30000t bulk carrier, 11800t bulk carriers as examples, we get some useful conclusions for modeling problem of the superstructure's overall vibration. Modeling methods of the ship's overall vibration is also discussed, analyzing the advantages and disadvantages of one-dimensional beam model and three-dimensional finite element model. When calculating on the ship's overall vibration, we can choose different models according to various conditions...