Numerical Simulation And Experimental Study On The Vibration Characteristics Of The Ship Stern Structure

The vibration characteristics of the ship will greatly affect its availability and habitability.As an important indicator of the performance of the hull structure,the vibration characteristic are getting more and more concern by shipowners and shipbuliding sectors.Harmfull vibration mainly occurs in the stern of the hull,which is the main arrangement area of power machinery and propulsion units.And therefore the vibration characteristic of stern is always in the focus of attention of the researchers.For this reason,the vibration characteristics of a ship stern structure model are studied in this thesis.And the results would provide more reference for the calculation and analysis of the vibration characteristics of the stern.Major research work done by this thesis are as follows:(1)The one-dimensional beam model,hybrid finite element models and separate stern model with different lengths were established.Based on the analysis of the vibration characteristics of the whole,correctness of the finite element model has been verified.On the basis of results of stern vibration from the three kinds of model,the principle of selection of the length of the stern for analysis of stern vibtration was carried out.Then the vibration characteristics of the stern structure were analyzed by using method of effective modal mass.(2)Taking local plated grillage as analytic target,the differences between global and local model calculation results of local vibration were studied.Principle of finite element mesh size was discussed by numerical analysis methods.The different calculating methods to solve problems of fluid-structure interaction vibration in external-unbounded fluid domain and interior-bounded fluid domain were compared and analyzed.The effect of draft on the vibration characteristics of structure was discussed under the plate which contacts with water by one side and both sides.And then,the influences of prestressing on the vibration characteristics of the plate and phase of excitation on the response characteristics of the plate were discussed.(3)The similarity criterion for ship dynamic model design was analyzed and verified by using numerical calculation methods,which is aimed at providing guidance on the ship dynamic model design.The vibration characteristics of a stiffened panels was studied by experimental and numerical methods.Comparison of the results by these two methods was carried out to verify the accuracy of numerical method.